电气工程及其自动化 外文翻译 外文文献 英文文献 电力系统的简介
电气工程及自动化专业英语考试翻译课文Electric Power Systems 电力系统3.1
Section 1 Introduction 第一节介绍The modern society depends on the electricity supply more heavily than ever before.现代社会比以往任何时候对电力供应的依赖更多。
It can not be imagined what the world should be if the electricity supply were interrupted all over the world. 如果中断了世界各地的电力供应,无法想像世界会变成什么样子Electric power systems (or electric energy systems), providing electricity to the modern society, have become indispensable components of the industrial world. 电力系统(或电力能源系统),提供电力到现代社会,已成为产业界的不可缺少的组成部分。
The first complete electric power system (comprising a generator, cable, fuse, meter, and loads) was built by Thomas Edison –the historic Pearl Street Station in New York City which began operation in September 1882. 托马斯爱迪生建立了世界上第一个完整的电力系统(包括发电机,电缆,熔断器,计量,并加载)它就是位于纽约市具有历史意义的珍珠街的发电厂始于1882年9月运作。
This was a DC system consisting of a steam-engine-driven DC generator supplying power to 59 customers within an area roughly 1.5 km in radius. The load, which consisted entirely of incandescent lamps, was supplied at 110 V through an underground cable system. 这是一个直流系统,由一个蒸汽发动机驱动的直流发电机其供电面积约1.5公里至59范围内的客户。
电气工程及其自动化 英文教材
电气工程及其自动化英文教材Electrical Engineering and Automation: An Introduction.Electrical engineering, often referred to as EE, is a broad field of engineering that deals with the design, development, and operation of electrical systems and equipment. Automation, on the other hand, is the technology used to control and monitor these systems, ensuring their efficient and reliable operation. Combined, electrical engineering and automation form a powerful technology that drives modern society, powering homes, businesses, and industries worldwide.Foundations of Electrical Engineering.Electrical engineering began in the late 19th century with the groundbreaking discoveries of Michael Faraday, Thomas Edison, and other pioneers. Since then, it has evolved significantly, incorporating advances in physics, mathematics, and computer science. The fundamentalprinciples of electrical engineering include electricity and magnetism, which are exploited in a wide range of applications.Automation: The Next Evolution.Automation has been a key driver of industrial revolution, enabling companies to increase productivity, reduce costs, and enhance safety. Automation systemsutilize sensors, actuators, controllers, and other components to monitor and control various processes. These systems can be programmed to perform complex tasks, eliminating the need for human intervention.Applications of Electrical Engineering and Automation.The applications of electrical engineering and automation are vast and diverse. They are found in almost every industry, from manufacturing to healthcare to transportation. In manufacturing, for example, automation systems are used to control robots that assemble parts, inspect quality, and package products. In healthcare, EEand automation are used in diagnostic equipment, patient monitoring systems, and even remote surgeries. In transportation, they are integral to aircraft, automobiles, and rail systems, ensuring safe and efficient travel.Challenges and Opportunities.As electrical engineering and automation continue to advance, they present both challenges and opportunities. One challenge is the complexity of modern systems, which require highly skilled engineers to design, maintain, and troubleshoot. Another challenge is the integration of new technologies, such as renewable energy sources and smart grids, into existing infrastructure.However, these challenges also present opportunities. The increasing demand for electrical engineers and automation specialists creates job opportunities in a wide range of industries. Additionally, advances in technology are enabling the development of more efficient, sustainable, and intelligent systems that can help address global issues such as climate change and resource scarcity.Conclusion.Electrical engineering and automation are essential to modern society, powering our homes, businesses, and industries. As we continue to push the boundaries of technology, it's important to recognize the fundamental principles and applications of EE and automation. By doing so, we can ensure that we are well-prepared to meet the challenges and seize the opportunities that lie ahead.。
电气工程及其自动化专业英语介绍
电气工程及其自动化专业英语介绍Introduction:Electrical Engineering and its Automation is a specialized field that combines the principles of electrical engineering with automation technology. This article aims to provide an overview of this discipline and its importance in various industries.I. Importance of Electrical Engineering and its Automation:1.1 Advancements in technology: Electrical Engineering and its Automation play a vital role in the development of new technologies. It enables the design and implementation of innovative electrical systems and automation solutions.1.2 Efficiency and productivity: By optimizing electrical systems and automating processes, this discipline helps in improving efficiency and productivity in industries such as manufacturing, power generation, and transportation.1.3 Safety and reliability: Electrical Engineering and its Automation ensure the safety and reliability of electrical systems by incorporating protective measures and fault detection mechanisms.II. Key Concepts in Electrical Engineering and its Automation:2.1 Electrical circuits and systems: This field extensively deals with the analysis and design of electrical circuits and systems. It includes topics such as circuit theory, electronic devices, and power systems.2.2 Control systems: Control systems are an integral part of automation. This area focuses on designing algorithms and controllers to regulate and optimize the behavior of dynamic systems.2.3 Programmable Logic Controllers (PLCs): PLCs are widely used in industrial automation. They are programmable devices that control and monitor various processes, ensuring seamless operation and fault detection.III. Applications of Electrical Engineering and its Automation:3.1 Power generation and distribution: Electrical Engineering and its Automation are crucial in the generation, transmission, and distribution of electrical power. It involves designing efficient power systems, grid management, and renewable energy integration.3.2 Industrial automation: This discipline plays a significant role in automating industrial processes, improving efficiency, and reducing human intervention. It includes robotics, motion control, and process automation.3.3 Smart grids and energy management: Electrical Engineering and its Automation contribute to the development of smart grids, enabling efficient energy distribution, load management, and demand response systems.IV. Career Opportunities in Electrical Engineering and its Automation:4.1 Electrical engineer: Graduates in this field can work as electrical engineers, involved in the design, installation, and maintenance of electrical systems and automation solutions.4.2 Automation engineer: Automation engineers focus on designing and implementing control systems, PLC programming, and integrating automation technologies into various industries.4.3 Research and development: Electrical Engineering and its Automation offer ample opportunities for research and development in areas such as renewable energy, power electronics, and advanced control systems.V. Conclusion:In conclusion, Electrical Engineering and its Automation is a dynamic field that combines electrical engineering principles with automation technology. It plays a crucial role in advancing technology, improving efficiency, and ensuring the safety and reliability of electrical systems. Graduates in this field have diverse career opportunities in various industries. As technology continues to evolve, the importance of ElectricalEngineering and its Automation will only increase, making it an exciting and promising field of study.。
电气工程与自动化毕业论文中英文资料外文翻译
电气工程与自动化毕业论文中英文资料外文翻译The Transformer on load ﹠Introduction to DC MachinesIt has been shown that a primary input voltage 1V can be transformed to any desired open-circuit secondary voltage 2E by a suitable choice of turns ratio. 2E is available for circulating a load current impedance. For the moment, a lagging power factor will be considered. The secondary current and the resulting ampere-turns 22N I will change the flux, tending to demagnetize the core, reduce m Φ and with it 1E . Because the primary leakage impedance drop is so low, a small alteration to 1Ewill cause an appreciable increase of primary current from 0I to a new value of 1Iequal to ()()i jX R E V ++111/. The extra primary current and ampere-turns nearly cancel the whole of the secondary ampere-turns. This being so , the mutual flux suffers only a slight modification and requires practically the same net ampere-turns 10N I as on no load. The total primary ampere-turns are increased by an amount 22N I necessary to neutralize the same amount of secondary ampere-turns. In thevector equation , 102211N I N I N I =+; alternatively, 221011N I N I N I -=. At full load,the current 0I is only about 5% of the full-load current and so 1I is nearly equalto 122/N N I . Because in mind that 2121/N N E E =, the input kV A which is approximately 11I E is also approximately equal to the output kV A, 22I E .The physical current has increased, and with in the primary leakage flux towhich it is proportional. The total flux linking the primary ,111Φ=Φ+Φ=Φm p , isshown unchanged because the total back e.m.f.,(dt d N E /111Φ-)is still equal and opposite to 1V . However, there has been a redistribution of flux and the mutual component has fallen due to the increase of 1Φ with 1I . Although the change is small, the secondary demand could not be met without a mutual flux and e.m.f.alteration to permit primary current to change. The net flux s Φlinking thesecondary winding has been further reduced by the establishment of secondaryleakage flux due to 2I , and this opposes m Φ. Although m Φ and 2Φ are indicatedseparately , they combine to one resultant in the core which will be downwards at theinstant shown. Thus the secondary terminal voltage is reduced to dt d N V S /22Φ-=which can be considered in two components, i.e. dt d N dt d N V m //2222Φ-Φ-=orvectorially 2222I jX E V -=. As for the primary, 2Φ is responsible for a substantiallyconstant secondary leakage inductance222222/Λ=ΦN i N . It will be noticed that the primary leakage flux is responsible for part of the change in the secondary terminal voltage due to its effects on the mutual flux. The two leakage fluxes are closely related; 2Φ, for example, by its demagnetizing action on m Φ has caused the changes on the primary side which led to the establishment of primary leakage flux.If a low enough leading power factor is considered, the total secondary flux and the mutual flux are increased causing the secondary terminal voltage to rise with load. p Φ is unchanged in magnitude from the no load condition since, neglecting resistance, it still has to provide a total back e.m.f. equal to 1V . It is virtually the same as 11Φ, though now produced by the combined effect of primary and secondary ampere-turns. The mutual flux must still change with load to give a change of 1E and permit more primary current to flow. 1E has increased this time but due to the vector combination with 1V there is still an increase of primary current.Two more points should be made about the figures. Firstly, a unity turns ratio has been assumed for convenience so that '21E E =. Secondly, the physical picture is drawn for a different instant of time from the vector diagrams which show 0=Φm , if the horizontal axis is taken as usual, to be the zero time reference. There are instants in the cycle when primary leakage flux is zero, when the secondary leakage flux is zero, and when primary and secondary leakage flux is zero, and when primary and secondary leakage fluxes are in the same sense.The equivalent circuit already derived for the transformer with the secondary terminals open, can easily be extended to cover the loaded secondary by the addition of the secondary resistance and leakage reactance.Practically all transformers have a turns ratio different from unity although such an arrangement is sometimes employed for the purposes of electrically isolating one circuit from another operating at the same voltage. To explain the case where 21N N ≠ the reaction of the secondary will be viewed from the primary winding. The reaction is experienced only in terms of the magnetizing force due to the secondary ampere-turns. There is no way of detecting from the primary side whether 2I is large and 2N small or vice versa, it is the product of current and turns which causesthe reaction. Consequently, a secondary winding can be replaced by any number of different equivalent windings and load circuits which will give rise to an identical reaction on the primary .It is clearly convenient to change the secondary winding to an equivalent winding having the same number of turns 1N as the primary.With 2N changes to 1N , since the e.m.f.s are proportional to turns, 2212)/('E N N E = which is the same as 1E .For current, since the reaction ampere turns must be unchanged 1222'''N I N I = must be equal to 22N I .i.e. 2122)/(I N N I =.For impedance , since any secondary voltage V becomes V N N )/(21, and secondary current I becomes I N N )/(12, then any secondary impedance, including load impedance, must becomeI V N N I V /)/('/'221=. Consequently,22212)/('R N N R = and 22212)/('X N N X = . If the primary turns are taken as reference turns, the process is called referring to the primary side.There are a few checks which can be made to see if the procedure outlined is valid.For example, the copper loss in the referred secondary winding must be the same as in the original secondary otherwise the primary would have to supply a differentloss power. ''222R I must be equal to 222R I . )222122122/()/(N N R N N I •• does infact reduce to 222R I .Similarly the stored magnetic energy in the leakage field)2/1(2LI which is proportional to 22'X I will be found to check as ''22X I . The referred secondary 2212221222)/()/(''I E N N I N N E I E kVA =•==.The argument is sound, though at first it may have seemed suspect. In fact, if the actual secondary winding was removed physically from the core and replaced by the equivalent winding and load circuit designed to give the parameters 1N ,'2R ,'2X and '2I , measurements from the primary terminals would be unable to detect any difference in secondary ampere-turns, kVA demand or copper loss, under normal power frequency operation.There is no point in choosing any basis other than equal turns on primary andreferred secondary, but it is sometimes convenient to refer the primary to the secondary winding. In this case, if all the subscript 1’s are interchanged for the subscript 2’s, the necessary referring constants are easily found; e.g. 2'1R R ≈,21'X X ≈; similarly 1'2R R ≈ and 12'X X ≈.The equivalent circuit for the general case where 21N N ≠ except that m r hasbeen added to allow for iron loss and an ideal lossless transformation has been included before the secondary terminals to return '2V to 2V .All calculations of internal voltage and power losses are made before this ideal transformation is applied. The behaviour of a transformer as detected at both sets of terminals is the same as the behaviour detected at the corresponding terminals of this circuit when the appropriate parameters are inserted. The slightly different representation showing the coils 1N and 2N side by side with a core in between is only used for convenience. On the transformer itself, the coils are , of course , wound round the same core.Very little error is introduced if the magnetising branch is transferred to the primary terminals, but a few anomalies will arise. For example ,the current shown flowing through the primary impedance is no longer the whole of the primary current.The error is quite small since 0I is usually such a small fraction of 1I . Slightlydifferent answers may be obtained to a particular problem depending on whether or not allowance is made for this error. With this simplified circuit, the primary and referred secondary impedances can be added to give:221211)/(Re N N R R += and 221211)/(N N X X Xe +=It should be pointed out that the equivalent circuit as derived here is only valid for normal operation at power frequencies; capacitance effects must be taken into account whenever the rate of change of voltage would give rise to appreciablecapacitance currents, dt CdV I c /=. They are important at high voltages and atfrequencies much beyond 100 cycles/sec. A further point is not the only possible equivalent circuit even for power frequencies .An alternative , treating the transformer as a three-or four-terminal network, gives rise to a representation which is just as accurate and has some advantages for the circuit engineer who treats all devices as circuit elements with certain transfer properties. The circuit on this basiswould have a turns ratio having a phase shift as well as a magnitude change, and the impedances would not be the same as those of the windings. The circuit would not explain the phenomena within the device like the effects of saturation, so for an understanding of internal behaviour .There are two ways of looking at the equivalent circuit:(a) viewed from the primary as a sink but the referred load impedance connected across '2V ,or(b) viewed from the secondary as a source of constant voltage 1V with internal drops due to 1Re and 1Xe . The magnetizing branch is sometimes omitted in this representation and so the circuit reduces to a generator producing a constant voltage 1E (actually equal to 1V ) and having an internal impedance jX R + (actually equal to 11Re jXe +).In either case, the parameters could be referred to the secondary winding and this may save calculation time .The resistances and reactances can be obtained from two simple light load tests. Introduction to DC MachinesDC machines are characterized by their versatility. By means of various combination of shunt, series, and separately excited field windings they can be designed to display a wide variety of volt-ampere or speed-torque characteristics for both dynamic and steadystate operation. Because of the ease with which they can be controlled , systems of DC machines are often used in applications requiring a wide range of motor speeds or precise control of motor output.The essential features of a DC machine are shown schematically. The stator has salient poles and is excited by one or more field coils. The air-gap flux distribution created by the field winding is symmetrical about the centerline of the field poles. This axis is called the field axis or direct axis.As we know , the AC voltage generated in each rotating armature coil is converted to DC in the external armature terminals by means of a rotating commutator and stationary brushes to which the armature leads are connected. The commutator-brush combination forms a mechanical rectifier, resulting in a DCarmature voltage as well as an armature m.m.f. wave which is fixed in space. The brushes are located so that commutation occurs when the coil sides are in the neutral zone , midway between the field poles. The axis of the armature m.m.f. wave then in 90 electrical degrees from the axis of the field poles, i.e., in the quadrature axis. In the schematic representation the brushes are shown in quarature axis because this is the position of the coils to which they are connected. The armature m.m.f. wave then is along the brush axis as shown.. (The geometrical position of the brushes in an actual machine is approximately 90 electrical degrees from their position in the schematic diagram because of the shape of the end connections to the commutator.)The magnetic torque and the speed voltage appearing at the brushes are independent of the spatial waveform of the flux distribution; for convenience we shall continue to assume a sinusoidal flux-density wave in the air gap. The torque can then be found from the magnetic field viewpoint.The torque can be expressed in terms of the interaction of the direct-axis air-gapflux per pole d Φ and the space-fundamental component 1a F of the armature m.m.f.wave . With the brushes in the quadrature axis, the angle between these fields is 90 electrical degrees, and its sine equals unity. For a P pole machine 12)2(2a d F P T ϕπ=In which the minus sign has been dropped because the positive direction of thetorque can be determined from physical reasoning. The space fundamental 1a F ofthe sawtooth armature m.m.f. wave is 8/2π times its peak. Substitution in above equation then givesa d a a d a i K i m PC T ϕϕπ==2 Where a i =current in external armature circuit;a C =total number of conductors in armature winding;m =number of parallel paths through winding;Andm PC K aa π2=Is a constant fixed by the design of the winding.The rectified voltage generated in the armature has already been discussedbefore for an elementary single-coil armature. The effect of distributing the winding in several slots is shown in figure ,in which each of the rectified sine waves is the voltage generated in one of the coils, commutation taking place at the moment when the coil sides are in the neutral zone. The generated voltage as observed from the brushes is the sum of the rectified voltages of all the coils in series between brushesand is shown by the rippling line labeled a e in figure. With a dozen or socommutator segments per pole, the ripple becomes very small and the average generated voltage observed from the brushes equals the sum of the average values ofthe rectified coil voltages. The rectified voltage a e between brushes, known also asthe speed voltage, ism d a m d a a W K W m PC e ϕϕπ==2 Where a K is the design constant. The rectified voltage of a distributed winding has the same average value as that of a concentrated coil. The difference is that the ripple is greatly reduced.From the above equations, with all variable expressed in SI units:m a a Tw i e =This equation simply says that the instantaneous electric power associated with the speed voltage equals the instantaneous mechanical power associated with the magnetic torque , the direction of power flow being determined by whether the machine is acting as a motor or generator.The direct-axis air-gap flux is produced by the combined m.m.f. f f i N ∑ of the field windings, the flux-m.m.f. characteristic being the magnetization curve for the particular iron geometry of the machine. In the magnetization curve, it is assumed that the armature m.m.f. wave is perpendicular to the field axis. It will be necessary to reexamine this assumption later in this chapter, where the effects of saturation are investigated more thoroughly. Because the armature e.m.f. is proportional to flux times speed, it is usually more convenient to express the magnetization curve in termsof the armature e.m.f. 0a e at a constant speed 0m w . The voltage a e for a given fluxat any other speed m w is proportional to the speed,i.e. 00a m m a e w w e =Figure shows the magnetization curve with only one field winding excited. This curve can easily be obtained by test methods, no knowledge of any design details being required.Over a fairly wide range of excitation the reluctance of the iron is negligible compared with that of the air gap. In this region the flux is linearly proportional to the total m.m.f. of the field windings, the constant of proportionality being the direct-axis air-gap permeance.The outstanding advantages of DC machines arise from the wide variety of operating characteristics which can be obtained by selection of the method of excitation of the field windings. The field windings may be separately excited from an external DC source, or they may be self-excited; i.e., the machine may supply its own excitation. The method of excitation profoundly influences not only the steady-state characteristics, but also the dynamic behavior of the machine in control systems.The connection diagram of a separately excited generator is given. The required field current is a very small fraction of the rated armature current. A small amount of power in the field circuit may control a relatively large amount of power in the armature circuit; i.e., the generator is a power amplifier. Separately excited generators are often used in feedback control systems when control of the armature voltage over a wide range is required. The field windings of self-excited generators may be supplied in three different ways. The field may be connected in series with the armature, resulting in a shunt generator, or the field may be in two sections, one of which is connected in series and the other in shunt with the armature, resulting in a compound generator. With self-excited generators residual magnetism must be present in the machine iron to get the self-excitation process started.In the typical steady-state volt-ampere characteristics, constant-speed primemovers being assumed. The relation between the steady-state generated e.m.f. a Eand the terminal voltage t V isa a a t R I E V -=Where a I is the armature current output and a R is the armature circuitresistance. In a generator, a E is large than t V ; and the electromagnetic torque T is acountertorque opposing rotation.The terminal voltage of a separately excited generator decreases slightly with increase in the load current, principally because of the voltage drop in the armature resistance. The field current of a series generator is the same as the load current, so that the air-gap flux and hence the voltage vary widely with load. As a consequence, series generators are not often used. The voltage of shunt generators drops off somewhat with load. Compound generators are normally connected so that the m.m.f. of the series winding aids that of the shunt winding. The advantage is that through the action of the series winding the flux per pole can increase with load, resulting in a voltage output which is nearly constant. Usually, shunt winding contains many turns of comparatively heavy conductor because it must carry the full armature current of the machine. The voltage of both shunt and compound generators can be controlled over reasonable limits by means of rheostats in the shunt field. Any of the methods of excitation used for generators can also be used for motors. In the typical steady-state speed-torque characteristics, it is assumed that the motor terminals are supplied froma constant-voltage source. In a motor the relation between the e.m.f. a E generated inthe armature and the terminal voltage t V isa a a t R I E V +=Where a I is now the armature current input. The generated e.m.f. a E is nowsmaller than the terminal voltage t V , the armature current is in the oppositedirection to that in a motor, and the electromagnetic torque is in the direction to sustain rotation of the armature.In shunt and separately excited motors the field flux is nearly constant. Consequently, increased torque must be accompanied by a very nearly proportional increase in armature current and hence by a small decrease in counter e.m.f. to allow this increased current through the small armature resistance. Since counter e.m.f. is determined by flux and speed, the speed must drop slightly. Like the squirrel-cage induction motor ,the shunt motor is substantially a constant-speed motor having about 5 percent drop in speed from no load to full load. Starting torque and maximum torque are limited by the armature current that can be commutatedsuccessfully.An outstanding advantage of the shunt motor is ease of speed control. With a rheostat in the shunt-field circuit, the field current and flux per pole can be varied at will, and variation of flux causes the inverse variation of speed to maintain counter e.m.f. approximately equal to the impressed terminal voltage. A maximum speed range of about 4 or 5 to 1 can be obtained by this method, the limitation again being commutating conditions. By variation of the impressed armature voltage, very wide speed ranges can be obtained.In the series motor, increase in load is accompanied by increase in the armature current and m.m.f. and the stator field flux (provided the iron is not completely saturated). Because flux increases with load, speed must drop in order to maintain the balance between impressed voltage and counter e.m.f.; moreover, the increase in armature current caused by increased torque is smaller than in the shunt motor because of the increased flux. The series motor is therefore a varying-speed motor with a markedly drooping speed-load characteristic. For applications requiring heavy torque overloads, this characteristic is particularly advantageous because the corresponding power overloads are held to more reasonable values by the associated speed drops. Very favorable starting characteristics also result from the increase in flux with increased armature current.In the compound motor the series field may be connected either cumulatively, so that its.m.m.f.adds to that of the shunt field, or differentially, so that it opposes. The differential connection is very rarely used. A cumulatively compounded motor has speed-load characteristic intermediate between those of a shunt and a series motor, the drop of speed with load depending on the relative number of ampere-turns in the shunt and series fields. It does not have the disadvantage of very high light-load speed associated with a series motor, but it retains to a considerable degree the advantages of series excitation.The application advantages of DC machines lie in the variety of performance characteristics offered by the possibilities of shunt, series, and compound excitation. Some of these characteristics have been touched upon briefly in this article. Stillgreater possibilities exist if additional sets of brushes are added so that other voltages can be obtained from the commutator. Thus the versatility of DC machine systems and their adaptability to control, both manual and automatic, are their outstanding features.中文翻译负载运行的变压器及直流电机导论通过选择合适的匝数比,一次侧输入电压1V 可任意转换成所希望的二次侧开路电压2E 。
电气工程及其自动化专业 外文文献 英文文献 外文翻译 plc方面
1、外文原文(复印件)A: Fundamentals of Single-chip MicrocomputerTh e si ng le-ch i p mi cr oc om pu ter is t he c ul mi nat i on o f bo th t h e d ev el op me nt o f th e d ig it al com p ut er an d t he int e gr at ed ci rc ui ta r gu ab ly th e t ow m os t s i gn if ic ant i nv en ti on s o f t h e 20t h c en tu ry[1].Th es e to w typ e s of a rc hi te ctu r e ar e fo un d i n s in gl e-ch ip m i cr oc om pu te r. So m e em pl oy t he sp l it p ro gr am/d ata me mo ry o f th e H a rv ar d ar ch it ect u re, sh ow n i n -5A, ot he rs fo ll ow th e ph i lo so ph y, w i de ly a da pt ed fo r g en er al-p ur pos e c om pu te rs an d m i cr op ro ce ss or s, o f m a ki ng no lo gi c al di st in ct io n b e tw ee n p ro gr am a n d da t a m em ory a s i n th e Pr in cet o n ar ch it ec tu re,sh ow n in-5A.In g en er al te r ms a s in gl e-chi p m ic ro co mp ut er i sc h ar ac te ri zed b y the i nc or po ra tio n of al l t he uni t s o f a co mp ut er i n to a s in gl e dev i ce, as s ho wn in Fi g3-5A-3.-5A-1 A Harvard type-5A. A conventional Princeton computerFig3-5A-3. Principal features of a microcomputerRead only memory (ROM).R OM i s u su al ly f or th e p er ma ne nt, n o n-vo la ti le s tor a ge o f an a pp lic a ti on s pr og ra m .M an ym i cr oc om pu te rs an d mi cr oc on tr ol le r s a re in t en de d fo r h ig h-v ol ume a p pl ic at io ns a nd h en ce t he e co nom i ca l ma nu fa ct ure of t he d ev ic es r e qu ir es t ha t the co nt en ts o f the pr og ra m me mo ry b e co mm it te dp e rm an en tl y d ur in g th e m an uf ac tu re o f c hi ps . Cl ear l y, th is im pl ie sa ri g or ou s a pp roa c h t o R OM co de d e ve lo pm en t s in ce c ha ng es ca nn otb e m ad e af te r man u fa ct ur e .T hi s d e ve lo pm en t pr oce s s ma y in vo lv e e m ul at io n us in g a s op hi st ic at ed deve lo pm en t sy st em w i th a ha rd wa re e m ul at io n ca pa bil i ty a s we ll a s th e u se of po we rf ul so ft wa re t oo ls.So me m an uf act u re rs p ro vi de ad d it io na l RO M opt i on s byi n cl ud in g i n th ei r ra ng e de vi ce s wi th (or i nt en de d fo r us e wi th) u s er pr og ra mm ab le m em or y. Th e s im p le st of th es e i s us ua ll y d ev ice w h ic h ca n op er ate in a m ic ro pr oce s so r mo de b y usi n g so me o f th e i n pu t/ou tp ut li ne s as a n ad dr es s an d da ta b us f or acc e ss in g e xt er na l m e mo ry. T hi s t ype o f d ev ic e c an b e ha ve fu nc ti on al l y a s t he si ng le c h ip mi cr oc om pu te r fr om wh ic h i t i s de ri ve d a lb eit w it h r es tr ic ted I/O an d a mo di fie d e xt er na l ci rcu i t. T he u se o f t h es e RO Ml es sd e vi ce s is c om mo n e ve n in p ro du ct io n c ir cu it s wh er e t he v ol um e do es n o t ju st if y th e d e ve lo pm en t co sts of c us to m on-ch i p RO M[2];t he re c a n st il l b e a si g ni fi ca nt s a vi ng in I/O a nd ot he r c hi ps co mp ar ed t o a c on ve nt io nal mi cr op ro ce ss or b as ed c ir cu it. M o re e xa ctr e pl ac em en t fo r RO M d ev ic es c an b e o bt ai ne d in t he f o rm o f va ri an ts w i th 'pi gg y-ba ck'EP RO M(Er as ab le p ro gr am ma bl e ROM)s oc ke ts o rd e vi ce s w it h EP ROM i ns te ad o f R OM 。
电气工程及其自动化专业外文文献英文文献外文翻译方面
1、 外文原文(复印件)A: Fundamentals of Single-chip MicrocomputerT h e sin gle -ch ip mi c ro co m p u t e r is t h e cu lm in at io n of b ot h t h e d e ve lo p me nt of t h e d ig ita l co m p u t e r a n d t h e i nte g rated c ircu it a rgu ab l y t h e to w mo st s ign if i cant i nve nt i o n s of t h e 20t h c e nt u ry [1].T h ese to w t yp e s of arch ite ct u re are fo u n d in s in gle -ch ip m i cro co m p u te r. S o m e e mp l oy t h e sp l it p ro gra m /d at a m e m o r y of t h e H a r va rd arch ite ct u re , s h o wn in -5A , ot h e rs fo l lo w t h e p h i lo so p hy, wid e l y ad a p ted fo r ge n e ral -p u rp o se co m p u te rs an d m i cro p ro ce ss o rs , of m a kin g n o l o g i ca l d i st in ct i o n b et we e n p ro gra m an d d ata m e m o r y as in t h e P rin c eto n a rch ite ct u re , sh o wn in -5A.In ge n e ra l te r m s a s in g le -ch ip m ic ro co m p u t e r is ch a ra cte r ized b y t h e in co r p o rat io n of all t h e u n its of a co mp u te r into a s in gle d e vi ce , as s h o w n in F i g3-5A-3.-5A-1A Harvard type-5A. A conventional Princeton computerProgrammemory Datamemory CPU Input& Output unitmemoryCPU Input& Output unitResetInterruptsPowerFig3-5A-3. Principal features of a microcomputerRead only memory (ROM).RO M is u su a l l y fo r t h e p e r m an e nt , n o n -vo lat i le sto rage of an ap p l i cat io n s p ro g ram .M a ny m i c ro co m p u te rs a n d m i cro co nt ro l le rs are inte n d ed fo r h i gh -vo lu m e ap p l i cat io n s a n d h e n ce t h e e co n o m i cal man u fa c t u re of t h e d e vi ces re q u ires t h at t h e co nt e nts of t h e p ro gra m me mo r y b e co mm i ed p e r m a n e nt l y d u r in g t h e m a n u fa ct u re of c h ip s . C lea rl y, t h i s imp l ies a r i go ro u s ap p ro a ch to ROM co d e d e ve lo p m e nt s in ce ch an ges can n o t b e mad e af te r m an u fa ct u re .T h i s d e ve l o p m e nt p ro ces s m ay i nvo l ve e mu l at i o n u sin g a so p h ist icated d e ve lo p m e nt syste m wit h a h ard wa re e mu l at i o n capab i l it y as we ll as t h e u s e of p o we rf u l sof t war e to o l s.So m e m an u fa ct u re rs p ro vi d e ad d it i o n a l ROM o p t io n s b y in clu d in g in t h e i r ran ge d e v ic es w it h (o r inte n d ed fo r u s e wit h ) u se r p ro g ram m a b le m e mo r y. T h e s im p lest of t h e se i s u su a l l y d e v i ce wh i ch can o p e rat e in a m i cro p ro ce s so r mo d e b y u s in g s o m e of t h e in p u t /o u t p u t l in es as an ad d res s a n d d ata b u s fo r a cc es sin g exte rn a l m e m o r y. T h is t yp e o f d e vi ce can b e h ave f u n ct i o n al l y as t h e s in gle ch ip m i cro co m p u t e r f ro m wh i ch it i s d e ri ved a lb e it wit h re st r icted I/O an d a m o d if ied exte rn a l c ircu it. T h e u s e of t h e se RO M le ss d e vi ces i s co mmo n e ve n in p ro d u ct io n circu i ts wh e re t h e vo lu m e d o e s n ot ju st if y t h e d e ve lo p m e nt co sts of cu sto m o n -ch ip ROM [2];t h e re ca n st i ll b e a si gn if i cant sav in g in I/O an d o t h e r ch ip s co m pared to a External Timing components System clock Timer/ Counter Serial I/O Prarallel I/O RAM ROMCPUco nve nt io n al m i c ro p ro ces so r b ased circ u it. M o re exa ct re p l a ce m e nt fo rRO M d e v ice s can b e o b tain ed in t h e fo rm of va ria nts w it h 'p i g g y-b a c k'E P ROM(E rasab le p ro gramm ab le ROM )s o cket s o r d e v ice s w it h E P ROMin stead of ROM 。
电气工程及其自动化外文翻译
The micro structure of low voltage distribution system BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to a novel and unique low voltage distribution system to wire a miniature structure with an electrical circuit which cooperates with bi-prong electrical fastening members which function as an electrical connector to plug an electric light bulb to the electrical circuit in the miniature structure. In particular, this invention relates to an easily installed electrical wiring system using an adhesive backed conductive foil tape as the bus bar for the system. The bi-prong electrical fastening devices can be plugged into and unplugged from the bus bar strips at any desired location.2. Disclosure of the Prior ArtIt is known in the art to utilize low voltage lighting systems for miniature structures. Typically, the wiring takes the form of insulated electrical conductors extending from a voltage source, such as a battery or step-down transformer, directly to a light bulb. Each light has its own pair of conductors which extend throughout the miniature structure.It is also known to install wiring within a miniature structure in the form of a distribution circuit having a plurality of junctions or connecting points wherein conductors are electrically connected at the connecting points by a soldered connection. Addition of a lamp or relocating a lamp requires soldering or mechanically disconnecting the lamp.Other known low voltage distribution systems utilize electrical connectors having female and male components. Other systems utilize a variety of electrical conductors and connecting devices, all of which require tools or following precise installation techniques.SUMMARY OF THE INVENTIONThe novel and unique low voltage distribution system for miniature structures, such as doll houses or other model buildings, of the present invention overcomes several disadvantages of the prior art. One advantage of the present invention is that a main bus bar for the distribution system is formed by a pair of elongated bus bar strips having a conductive metal foil top layer and an adhesive bottom layer. The strips are easily installed by peeling off a removable backing member exposing the adhesive layer. The bus bar strips are affixed to the walls of the miniature structure in a parallel spaced relationship. The distance between the center line of the strips is selected to be a predetermined distance. The predetermined distance is at least equal to the transverse width or geometrical dimension of the strips. Bi-prong electrical fastening devices having two sharp points are pushed into the bus bar, pierce and pass through the parallel strips, forming an electrical connection with the strips. The points engage the wall of the miniature structure and are held in place. A light bulb is connected by wires across the bi-prong plug.Another advantage is that the bus bar strips are easily formed into 90° angles or other angles by folding the strips to obtain the desired angle. Prior art devices require staples or adhesive holding devices to hold insulating wires. Depending on thedistribution system of the prior art devices, an electrical connection requires tools, soldering or some method of insuring a dependable mechanical and electrical connection.Another advantage of the present invention is that the bi-prong electrical fastening device is easily installed by pushing the device into the miniature structure wall in the same manner as a tack of similar device. If it is desired to remove or relocate a lamp, the bi-prong plug is easily pulled out and reinserted.Yet another advantage of the present invention is that branch bus bar circuits can be fabricated by folding the end against itself forming a mating terminal. The mating terminal is placed into contact at any desired location on the main bus bar to form sub-distribution circuits.A yet further advantage of the present invention is that a lamp can be attached to a bi-prong plug by winding wires together and forming a tight insulating seal therearound by use of a heat-shrinkable tube or cylinder.BRIEF DESCRIPTION OF THE DRAWINGThe foregoing and other advantages and features of the invention will be apparent from the following description of the preferred embodiment of the invention when considered together with the illustrations in the accompanying drawings and includes the following figures:FIG. 1 is a schematic diagram showing the low voltage distribution system having bi-prong plugs and lamp connected thereto;FIG. 2 is a perspective view of a contacting mating connection between a main bus bar and a branch bus bar;FIG. 3 is a pictorial representation of a doll house having a pair of spaced parallel elongated strips as the main bus bar and branch bus bar;FIG. 4 is a diagrammatic representation of a section of bus bar having a bi-prong electrical fastening device inserted therein;FIG. 5 is a section taken along section lines 5-5 of FIG. 4;FIGS. 6, 7 and 8 are an end, front and top view of a bi-prong electrical fastening device having a circular cross-section;FIGS. 9, 10 and 11 are an end, front and top view of a bi-prong electrical fastening device having a rectangular cross-section;FIG. 12 is a pictorial illustration of twisting an end of a conductor from a bi-prong electrical fastening device with the end of a conductor from a light bulb having a heat shrinkable tube strung on the conductors; andFIG. 13 is a wire lamp and bi-prong electrical fastening device with the heat-shrinkable sealing tube being shrunk to form a tight insulating seal around the twisted electrical connection illustrated in FIG. 12.DESCRIPTION OF THE PREFERRED EMBODIMENTThe schematic diagram of FIG. 1 includes a means for producing a low voltage signal such as, for example, a step down transformer 20. In the preferred embodiment, a primary winding 22 of transformer 20 is electrically connected across a 120 volt 60 hertz source. A secondary winding 24 produces a low voltage, 60 hertz signal thereacross such as 12 volts A.C. The low voltage source could be a direct currentsource such as batteries.The transformer 20 may include a detecting and limiting device 28 to detect and limit the current flow through the secondary winding 24. If the transformer becomes overloaded due to high current flow, the device 28 opens. A thermal cutout may be used as one such device. The transformer may be a 120/12 volt 60 hertz U.L. approved Class 2 transformer.A main bus bar, shown generally as 30, is electrically connected to the secondary winding 24 by electrical conductors 32.A branch bus bar, shown generally as 36, is attached or connected to the main bus bar30 through a pair of mating contacts shown as 40 and 42.Bi-prong electrical fastening devices shown as 50 are inserted into the bus bar to make electrical contact. Each bi-prong plug 50 has a lamp 52 connected thereto. The connections are made through sealed electrical connectors 54.FIG. 2 illustrates the main bus bar 30 is formed of two spaced parallel strips 56 and 58 each having a conductive metal foil top layer 60 and an adhesive bottom layer 62. The width of the strip is of a selected geometrical dimension. The bus bar's two elongated strips 56 and 58 are spaced with the center lines 64 and 66, respectively, spaced a predetermined distance. The predetermined distance, in the preferred embodiment, is at least equal to the width of strips 56 and 58.A branch bus bar having two elongated strips 70 and 72, which is of the same material and construction as strips 56 and 58, has the one end thereof folded back upon itself with the adhesive layer of the folded end in contact with and adhering to the adhesive layer of the unfolded bus bar strip to form coplanar mating contacts 74 and 76. The coplanar mating contacts 74 and 76 are in mating electrical contact with the conductive metal top foil 60. Pieces of adhesive tape 80 are affixed to mating contacts 74 and 76, and a piece of adhesive tape 82 is located between strips 56 and 72. A section of the miniature structure is shown as 86.FIG. 3 shows a miniature structure 90 having a main bus bar 92 and a branch bus bar 94. The mating connection is shown as 96. Several right angle turns in the bus bar are shown by 100. A typical wiring pattern extends through three stories.FIG. 4 shows a top view of a section 104 of the miniature structure having bus bar strips 56 and 58 adhered thereto. The strips 56 and 58 originally and a protective backing which was removed exposing the adhesive. A bi-prong electrical connecting 50 device has conductive fastening members 120 (shown in FIGS. 5 through 8) terminating in an output terminal 108. A pair of insulated electrical conductors 110 is attached to output terminal 108.An end sectional view of the bus bar strips 56 and 58 and bi-prong electrical connecting device 50 in FIG. 5 shows that the conductive fastening members 120 terminate in a tapered cutting edge or point 122 adapted to pierce and be driven through the bus bar forming an electrical connection therewith and into fastening engagement with a selected portion 104 of the miniature structure.The conductive fastening members 120 are spaced a predetermined distance apart and are parallel to each other. Each conductive fastening member 120 terminates in an output terminal 108 having conductors 110 soldered thereto. The housing or body 124of the bi-prong plug 50 is formed of insulating, cured epoxy well known in the art. FIGS. 6, 7 and 8 show a bi-prong electrical fastening member having a circular cross-section. The elements are shown in solid line with the body 124 shown in dashed line.FIGS. 9, 10 and 11 show a bi-prong electrical fastening member having a rectangular cross-section. The elements are shown in solid line with the body 124 shown in dashed line.FIG. 12 shows an electrical conductor 110 with a conductive end section 126 exposed and twisted together with the end of a conducting lead 128 from a lamp or light bulb 52. A heat-shrinkable tube or cylinder 130 is positioned around each joined connection of the conducting lead 128 and electrical conductor 110. The tube 130 has an axial length sufficient to encapsulate and form a tight, insulating fitting around the connection. FIG. 13 shows the tube 130 and wiring being exposed to a heat source 142 of the right temperature to cause the desired shrinkage.The system disclosed herein can be assembled into a lighting kit for use in a doll house or for other miniature structures such as that used with model trains, model cities and other hobby type structures. In the preferred embodiment, the kit comprises a transformer, copper tape with an adhesive backing, light bulbs, wires, spring clamps (used as connecting means 32 in FIG. 1) and heat shrinkable tubing.The connections for providing a 12 volt electrical signal from the two copper tapes and into a lamp or fixture in the structure is obtained by attaching one of the bi-prong plugs to the bulbs or lamps. The two prongs of the plug are pointed and are pressed into and through the copper tapes in a manner similar to insertion and removal of a two-prong fastener.Installation of the distribution system is fairly simple and can be done without use of tools or soldering equipment. This is of significance in the model or hobby market.It is also envisioned that the connecting means in FIG. 1 may well be a bi-prong electrical connecting device wherein the electrical conductors are connected to the output of the transformer.What is claimed is:1. A low voltage distribution system for a miniature structure comprisingmeans for producing a low voltage signal;a main bus bar formed of a conductive metal foil top layer and an adhesive bottom layer, said conductive metal foil having a pair of elongated bus bar strips each having a selected geometrical dimension across the width thereof, said strips being positioned in spaced parallel relationship wherein the spacing between the parallel center lines of each elongated bus bar strip is of a predetermined distance which is at least equal to said geometrical dimension and said adhesive layer being adapted to attach the main bus bar to a selected portion of a miniature structure with the conductive metal foil exposed;means for connecting the low voltage signal to the conductive metal foil layer and producing a voltage potential across said strips; andat least one bi-prong removable electrical fastening device formed of a pair of spacedconductive fastening members each of which are electrically connected to an output terminal, each of said fastening members terminating in an elongated tapered cutting edge, said tapered cutting edges being in spaced parallel relationship and having a dimension therebetween substantially equal to said predetermined distance, and which, when urged into fastening engagement with a said miniature structure, are adapted to pierce, form an elongated slit in and parallel to the center line of each bus bar and be driven through each of the bus bar strips of the main bus bar forming an electrical connection therewith and into fastening engagement with said selected portion of a said miniature structure located under the adhesive layer, and being adapted to terminate said electrical connection with each of the bus bar strips upon removal of the fastening member from fastening engagement with said selected portion of a miniature structure by slideably withdrawing the tapered edges from each bus bar strip leaving a slight elongated slit therein while enabling the strips to maintain a voltage potential thereacross independent of the elongated slit.2. The system of claim 1 wherein the means for producing a low voltage signal comprises a step down alternating current transformer.3. The system of claim 2 wherein the low voltage signal producing means includes means for detecting and limiting the current flow through the step down transformer.4. The system of claim 3 wherein the low voltage signal connecting means includesa pair of transformer leads; anda pair of spring clips electrically connected to the transformer leads and to the main bus bar.5. The system of claim 1 whereinsaid bi-prong electrical fastening device includes a pair of separate output terminals electrically connected to said spaced fastening members and having a geometrical distance therebetween which is substantially equal to said predetermined distance.6. The system of claim 5 further comprisinga second bi-prong electrical fastening device identical to said at least one bi-prong electrical fastening device and adapted to pierce and be driven through a different section of the main bus bar forming an electrical connection therewith and into fastening engagement with a selected section of a miniature structure.7. The system of claim 5 further comprisinga branch bus bar having a pair of elongated bus bar strips having a geometrical dimension across the width thereof which is substantially equal to said selected geometrical dimension, a conductive metal foil top layer and an adhesive bottom layer, said branch bus bar strips being positioned in a spaced parallel relationship wherein the spacing between the parallel center lines thereof is substantially equal to said predetermined distance, said branch bus bar strips each having one end thereof folded back upon itself with the adhesive layer of the folded end in contact with and adhering to the adhesive layer of the unfolded bus bar strip to form a coplanar mating contact with the conductive metal foil layer being located on the outer surface of the folded end, one of said mating contacts at the end of each bus bar strip being positioned in mating electrical contact with the conductive metal foil top layer of the main bus bar; anda second removable bi-prong electrical fastening device formed of a pair of spaced conductive fastening members electrically connected to an output terminal, each of said spaced conductive fastening members being electrically connected to a separate output terminal and each of which terminate in an elongated tapered cutting edge, said tapered cutting edges being in spaced parallel relationship and having a dimension therebetween substantially equal to said predetermined distance and which, when urged into fastening engagement with a said miniature structure, are adapted to pierce, form an elongated slit in and parallel to the center line of each branch bus bar strip and be driven through the elongated strips of the branch bus bar forming an electrical connection therewith and into fastening engagement with a section of a said miniature structure located under the adhesive layer, and being adapted to terminate said electrical connection from each of the branch bus bar strips upon removal of the second fastening device conductive fastening member from fastening engagement with said selected portion of a miniature structure by slideably withdrawing the tapered edges from each branch bus bar strip leaving a slight elongated slit therein while enabling the strip to maintain a voltage potential thereacross independent of the elongated slit.8. The system of claim 7 further comprisinga third bi-prong electrical fastening device identical to said second bi-prong electrical fastening device and adapted to pierce and be driven through the branch bus bar forming an electrical connection therewith and into fastening engagement with a selected section of a said miniature structure.9. The system of claim 3 further comprisinga pair of insulated electrical conductors wherein each conductor has one end thereof electrically attached to an output terminal and the other end of the conductor terminating with the conductive end section thereof exposed; anda light bulb capable of being illuminated by the low voltage signal, said light bulb having a pair of conducting leads extending therefrom with each end thereof electrically connected to one of the exposed conductor end sections forming an electrical circuit therewith.10. The system of claim 9 further comprisinga heat-shrinkable cylinder positioned around each joined connection of the conducting lead and electrical conductor, said cylinder having an axial length sufficient to encapsulate and form a tight insulating fitting around said electrical connection.11. A low voltage distribution system for wiring a miniature structure for electricity comprisinga step down voltage transformer adapted to be electrically connected to an alternating current voltage source having a voltage level higher than the desired distribution voltage level for producing a low voltage signal at the level desired for the distribution voltage;a first and second elongated bus bar strip, each having a selected geometrical dimension across the width thereof and formed of a conductive metal foil top layer and a bottom adhesive layer, said bus bar strips being affixed to a selected section of a said miniature structure and positioned in a spaced parallel relationship with apredetermined distance between the center lines of each strip being at least equal to said selected geometrical dimension;a pair of electrical connectors extending from the transformer to the bus bar strips for applying the low voltage signal across said bus bar strips having a plurality of bi-prong removable electrical fastening members terminating in a pair of spaced parallel elongated tapered cutting edges having a dimension therebetween substantially equal to said predetermined distance and which, when urged into fastening engagement with said miniature structure, is adapted to pierce, form an elongated slit in and parallel to the center line of each bus bar and be driven into and through the bus bar strips forming a plurality of parallel electrical connections therewith and into fastening engagement with a different selected section of a said miniature structure, each of which are located opposite the fastening member and under the bus bar strips and which is adapted to terminate said electrical connection with each of the bus bar strips upon removal of the fastening member from fastening engagement with said selected portion of a miniature structure by slideably withdrawing from each bus bar strip leaving a slight elongated slit therein while enabling the strips to maintain a voltage potential thereacross independent of the elongated slit; anda plurality of light bulbs each of which has a pair of conducting leads which are electrically connected across one of said bi-prong electrical fastening members, said light bulbs each being in parallel circuit connection to each other and being responsive to the low voltage signal applied across the bus bar to become illuminated.12. The system of claim 11 wherein the bi-prong electrical fastening member has a round cross-section.13. The system of claim 12 wherein the bi-prong electrical fastening member has a rectangular cross-section.14. A miniature structure low voltage distribution system having a main bus bar formed of a conductive metal foil layer which is affixed to the miniature structure by an adhesive bottom layer, said main bus bar having a pair of spaced parallel elongated bus bar strips each having a selected geometrical dimension across the width thereof and with the spacing between the center lines of the parallel strips being a predetermined distance, said distribution system comprisingat least one bi-prong removable electrical fastening device formed of a pair of spaced conductive fastening members each of which are electrically connected to an output terminal, each of said fastening members terminating in an elongated tapered cutting edge, said tapered cutting edges being in spaced parallel relationship and having a dimension therebetween substantially equal to said predetermined distance, and which, when urged into fastening engagement with a said miniature structure, are adapted to pierce, form an elongated slit in and parallel to the center line of each bus bar and be driven through each of the bus bar strips of the main bus bar forming an electrical connection therewith and into fastening engagement with said selected portion of a said miniature structure located under the adhesive layer, and being adapted to terminate said electrical connection with each of the bus bar strips upon removal of the fastening member from fastening engagement with said selected portion of aminiature structure by slideably withdrawing the tapered edges from each bus bar strip leaving a slight elongated slit therein while enabling the strips to maintain a voltage potential thereacross independent of the elongated slit.微型结构低压分配系统1.发明背景此项发明涉及到一项独特的低压分配系统,此系统为一个有着电子线路的微型结构,它包含着电力加速构件,其中的电子连接器使一个电灯泡安插在这个微型结构中。
电气工程的外文文献(及翻译)
电气工程的外文文献(及翻译)文献一:Electric power consumption prediction model based on grey theory optimized by genetic algorithms本文介绍了一种基于混合灰色理论与遗传算法优化的电力消耗预测模型。
该模型使用时间序列数据来建立模型,并使用灰色理论来解决数据的不确定性问题。
通过遗传算法的优化,模型能够更好地预测电力消耗,并取得了优异的预测结果。
此模型可以在大规模电力网络中使用,并具有较高的可行性和可靠性。
文献二:Intelligent control for energy-efficient operation of electric motors本文研究了一种智能控制方法,用于电动机的节能运行。
该方法提供了一种更高效的控制策略,使电动机能够在不同负载条件下以较低的功率运行。
该智能控制使用模糊逻辑方法来确定最佳的控制参数,并使用遗传算法来优化参数。
实验结果表明,该智能控制方法可以显著降低电动机的能耗,节省电能。
文献三:Fault diagnosis system for power transformers based on dissolved gas analysis本文介绍了一种基于溶解气体分析的电力变压器故障诊断系统。
通过对变压器油中的气体样品进行分析,可以检测和诊断变压器内部存在的故障类型。
该系统使用人工神经网络模型来对气体分析数据进行处理和分类。
实验结果表明,该系统可以准确地检测和诊断变压器的故障,并有助于实现有效的维护和管理。
文献四:Power quality improvement using series active filter based on iterative learning control technique本文研究了一种基于迭代研究控制技术的串联有源滤波器用于电能质量改善的方法。
电力系统自动化毕业论文中英文资料外文翻译
毕业设计(论文)外文资料翻译专业名称:电力系统自动化英文资料:INDUCTION MOTOR STARTING METHODSAbstract -Many methods can be used to start large AC induction motors. Choices such as full voltage, reduced voltage either by autotransformer or Wyes - Delta, a soft starter, or usage of an adjustable speed drive can all have potential advantages and trade offs. Reduced voltage starting can lower the starting torque and help prevent damage to the load. Additionally, power factor correction capacitors can be used to reduce the current, but care must be taken to size them properly. Usage of the wrong capacitors can lead to significant damage. Choosing the proper starting method for a motor will include an analysis of the power system as well as the starting load to ensure that the motor is designed to deliver the needed performance while minimizing its cost. This paper will examine the most common starting methods and their recommended applications.I. INTRODUCTIONThere are several general methods of starting induction motors: full voltage, reduced voltage, wyes-delta, and part winding types. The reduced voltage type can include solid state starters, adjustable frequency drives, and autotransformers. These, along with the full voltage, or across the line starting, give the purchaser a large variety of automotives when it comes to specifying the motor to be used in a given application. Each method has its own benefits, as well as performance trade offs. Proper selection will involve a thorough investigation of any power system constraints, the load to be accelerated and the overall cost of the equipment.In order for the load to be accelerated, the motor must generate greater torque than the load requirement. In general there are three points of interest on the motor's speed-torque curve. The first is locked-rotor torque (LRT) which is the minimum torque which the motor will develop at rest for all angular positions of the rotor. The second is pull-up torque (PUT) which is defined as the minimum torque developed by the motor during the period of acceleration from rest to the speed at which breakdown torque occurs. The last is the breakdown torque (BDT) which is defined as the maximum torque which the motor will develop. If any of these points are below the required load curve, then the motor will not start.The time it takes for the motor to accelerate the load is dependent on the inertia of the load and the margin between the torque of the motor and the load curve, sometimes called accelerating torque. In general, the longer the time it takes for the motor to accelerate the load, the more heat that will be generated in the rotor bars, shorting ring and the stator winding. This heat leads to additional stresses in these parts and can have an impaction motor life.II. FULL VOLTAGEThe full voltage starting method, also known as across the line starting, is the easiest method to employ, has the lowest equipment costs, and is the most reliable. This method utilizes a control to close a contactor and apply full line voltage to the motor terminals. This method will allow the motor to generate its highest starting torque and provide the shortest acceleration times.This method also puts the highest strain on the power system due to the high starting currents that can be typically six to seven times the normal full load current of the motor. If the motor is on a weak power system, the sudden high power draw can cause a temporary voltage drop, not only at the motor terminals, but the entire power bus feeding the starting motor. This voltage drop will cause a drop in the starting torque of the motor, and a drop in the torque of any other motor running on the power bus. The torque developed by an induction motor varies roughly as the square of the applied voltage. Therefore, depending on the amount of voltage drop, motors running on this weak power bus could stall. In addition, many control systems monitor under voltage conditions, a second potential problem that could take a running motor offline during a full voltage start. Besides electrical variation of the power bus, a potential physical disadvantage of an across the line starting is the sudden loading seen by the driven equipment. This shock loading due to transient torques which can exceed 600% of the locked rotor torque can increase the wear on the equipment, or even cause a catastrophic failure if the load can not handle the torques generated by the motor during staring.A. Capacitors and StartingInduction motors typically have very low power factor during starting and as a result have very large reactive power draw. See Fig. 2. This effect on the system can be reduced by adding capacitors to the motor during starting.The large reactive currents required by the motor lag the applied voltage by 90 electrical degrees. This reactive power doesn't create any measurable output, but is rather the energy required for the motor to function. The product of the applied system voltage and this reactive power component can be measured in V ARS (volt-ampere reactive). The capacitors act to supply a current that leads the applied voltage by 90 electrical degrees. The leading currents supplied by the capacitors cancel the laggingcurrent demanded by the motor, reducing the amount of reactive power required to be drawn from the power system.To avoid over voltage and motor damage, great care should be used to make sure that the capacitors are removed as the motor reaches rated speed, or in the event of a loss of power so that the motor will not go into a generator mode with the magnetizing currents provided from the capacitors. This will be expanded on in the next section and in the appendix.B. Power Factor CorrectionCapacitors can also be left permanently connected to raise the full load power factor. When used in this manner they are called power factor correction capacitors. The capacitors should never be sized larger than the magnetizing current of the motor unless they can be disconnected from the motor in the event of a power loss.The addition of capacitors will change the effective open circuit time constant of the motor. The time constant indicates the time required for remaining voltage in the motor to decay to 36.8% of rated voltage after the loss of power. This is typically one to three seconds without capacitors.With capacitors connected to the leads of the motor, the capacitors can continue to supply magnetizing current after the power to the motor has been disconnected. This is indicated by a longer time constant for the system. If the motor is driving a high inertia load, the motor can change over to generator action with the magnetizingCurrent from the capacitors and the shaft driven by the load. This can result in the voltage at the motor terminals actually rising to nearly 50% of rated voltage in some cases. If the power is reconnected before this voltage decays severe transients can be created which can cause significant switching currents and torques that can severely damage the motor and the driven equipment. An example of this phenomenon is outlined in the appendix.Ⅲ. REDUCED VOLTAGEEach of the reduced voltage methods are intended to reduce the impact of motor starting current on the power system by controlling the voltage that the motor sees atthe terminals. It is very important to know the characteristics of the load to be started when considering any form of reduced voltage starting. The motor manufacturer will need to have the speed torque curve and the inertia of the driven equipment when they validate their design. The curve can be built from an initial, or break away torque, as few as four other data points through the speed range, and the full speed torque for the starting condition. A centrifugal or square curve can be assumed in many cases, but there are some applications where this would be problematic. An example would be screw compressors which have a much higher torque requirement at lower speeds than the more common centrifugal or fan load. See Fig. 3. By understanding the details of the load to be started the manufacturer can make sure that the motor will be able to generate sufficient torque to start the load, with the starting method that is chosen.A. AutotransformerThe motor leads are connected to the lower voltage side of the transformer. The most common taps that are used are 80%, 65%, and 50%. At 50% voltage the current on the primary is 25% of the full voltage locked rotor amps. The motor is started with this reduced voltage, and then after a pre-set condition is reached the connection is switched to line voltage. This condition could be a preset time, current level, bus volts, or motor speed. The change over can be done in either a closed circuit transition, or an open circuit transition method. In the open circuit method the connection to the voltage is severed as it is changed from the reduced voltage to the line level. Care should be used to make sure that there will not be problems from transients due to the switching. This potential problem can be eliminated by using the closed circuit transition. With the closed circuit method there is a continuousVoltage applied to the motor. Another benefit with the autotransformer starting is in possible lower vibration and noise levels during starting.Since the torque generated by the motor will vary as the square of the applied voltage, great care should be taken to make sure that there will be sufficient accelerating torque available from the motor. A speed torque curve for the driven equipment along with the inertia should be used to verify the design of the motor. A good rule of thumb is to have a minimum of 10% of the rated full load torque of the motor as a margin at all points of the curve.Additionally, the acceleration time should be evaluated to make sure that the motor has sufficient thermal capacity to handle the heat generated due to the longeracceleration time.B. Solid State or Soft StartingThese devices utilize silicon controlled rectifiers or Scars. By controlling the firing angle of the SCR the voltage that the device produces can be controlled during the starting of the motor by limiting the flow of power for only part of the duration of the sine wave.The most widely used type of soft starter is the current limiting type. A current limit of 175% to 500% of full load current is programmed in to the device. It then will ramp up the voltage applied to the motor until it reaches the limit value, and will then hold that current as the motor accelerates.Tachometers can be used with solid state starters to control acceleration time. Voltage output is adjusted as required by the starter controller to provide a constant rate of acceleration.The same precautions in regards to starting torque should be followed for the soft starters as with the other reduced voltage starting methods. Another problem due to the firing angle of the SCR is that the motor could experience harmonic oscillating torques. Depending on the driven equipment, this could lead to exciting the natural frequency of the system.C. Adjustable Frequency DrivesThis type of device gives the greatest overall control and flexibility in starting induction motors giving the most torque for an amount of current. It is also the most costly.The drive varies not only the voltage level, but also the frequency, to allow the motor to operate on a constant volt per hertz level. This allows the motor to generate full load torque throughout a large speed range, up to 10:1. During starting, 150% of rated current is typical.This allows a significant reduction in the power required to start a load and reduces the heat generated in the motor, all of which add up to greater efficiency. Usage of the AFD also can allow a smaller motor to be applied due to the significant increase of torque available lower in the speed range. The motor should still be sizedlarger than the required horsepower of the load to be driven. The AFD allows a great degree of control in the acceleration of the load that is not as readily available with the other types of reduced voltage starting methods.The greatest drawback of the AFD is in the cost relative to the other methods. Drives are the most costly to employ and may also require specific motor designs to be used. Based on the output signal of the drive, filtered or unfiltered, the motor could require additional construction features. These construction features include insulated bearings, shaft grounding brushes, and insulated couplings due to potential shaft current from common mode voltage. Without these features, shaft currents, which circulate through the shaft to the bearing, through the motor frame and back, create arcing in the bearings that lead to premature bearing failure, this potential for arcing needs to be considered when applying a motor/drive package in a hazardous environment, Division2/Zone2.An additional construction feature of a motor used on an AFD may require is an upgraded insulation system on the motor windings. An unfiltered output signal from a drive can create harmonic voltage spikes in the motor, stressing the insulation of the motor windings.It is important to note that the features described pertain to motors which will be started and run on an AFD. If the drive is only used for starting the motor, these features may not be necessary. Consult with the motor manufacturer for application specific requirements.D. Primary Resistor or Reactor StartingThis method uses either a series resistor or reactor bank to be placed in the circuit with the motor. Resistor starting is more frequently used for smaller motors.When the motor is started, the resistor bank limits the flow of inrush current and provides for a voltage drop at the motor terminals. The resistors can be selected to provide voltage reductions up to 50%. As the motor comes up to speed, it develops a counter EMF (electro-magnetic field) that opposes the voltage applied to the motor. This further limits the inrush currents. As the inrush current diminishes, so does t>e voltage drop across the resistor bank allowing the torque generated by the motor to increase. At a predetermined time a device will short across the resistors and open the starting contactor effectively removing the resistor bank from the circuit. This provides for a closed transition and eliminates the concerns due to switchingtransients.Reactors will tend to oppose any sudden changes in current and therefore act to limit the current during starting. They will remain shorted after starting and provide a closed transition to line voltage.E .Star delta StartingThis approach started with the induction motor, the structure of each phase of the terminal are placed in the motor terminal box. This allows the motor star connection in the initial startup, and then re-connected into a triangle run. The initial start time when the voltage is reduced to the original star connection, the starting current and starting torque by 2 / 3. Depending on the application, the motor switch to the triangle in the rotational speed of between 50% and the maximum speed. Must be noted that the same problems, including the previously mentioned switch method, if the open circuit method, the transition may be a transient problem. This method is often used in less than 600V motor, the rated voltage 2.3kV and higher are not suitable for star delta motor start method.Ⅴ. INCREMENT TYPEThe first starting types that we have discussed have deal with the way the energy is applied to the motor. The next type deals with different ways the motor can be physically changed to deal with starting issues.Part WindingWith this method the stator of the motor is designed in such a way that it is made up of two separate windings. The most common method is known as the half winding method. As the name suggests, the stator is made up of two identical balanced windings. A special starter is configured so that full voltage can be applied to one half of the winding, and then after a short delay, to the second half. This method can reduce the starting current by 50 to 60%, but also the starting torque. One drawback to this method is that the motor heating on the first step of the operation is greater than that normally encountered on across-the-line start. Therefore the elapsed time on the first step of the part winding start should be minimized. This method also increases the magnetic noise of the motor during the first step.IV .ConclusionThere are many ways asynchronous motor starting, according to the constraints of power systems, equipment costs, load the boot device to select the best method. From the device point of view, was the first full-pressure launch the cheapest way, but it may increase the cost efficiency in the use of, or the power supply system in the region can not meet their needs. Effective way to alleviate the buck starts the power supply system, but at the expense of the cost of starting torque.These methods may also lead to increased motor sizes have led to produce the required load torque. Inverter can be eliminated by the above two shortcomings, but requires an additional increase in equipment costs. Understand the limitations of the application, and drives the starting torque and speed, allowing you for your application to determine the best overall configuration.英文资料翻译:异步电动机起动的方法摘要:大容量的交流异步电动机有多种启动方法。
电气工程及其自动化 外文翻译 外文文献 英文文献 电力系统的简介
Brief Introduction to The Electric Power SystemPart 1 Minimum electric power systemA minimum electric power system is shown in Fig.1-1, the system consists of an energy source, a prime mover, a generator, and a load.The energy source may be coal, gas, or oil burned in a furnace to heat water and generate steam in a boiler; it may be fissionable material which, in a nuclear reactor, will heat water to produce steam; it may be water in a pond at an elevation above the generating station; or it may be oil or gas burned in an internal combustion engine.The prime mover may be a steam-driven turbine, a hydraulic turbine or water wheel, or an internal combustion engine. Each one of these prime movers has the ability to convert energy in the form of heat, falling water, or fuel into rotation of a shaft, which in turn will drive the generator.The electrical load on the generator may be lights, motors, heaters, or other devices, alone or in combination. Probably the load will vary from minute to minute as different demands occur.The control system functions (are)to keep the speed of the machines substantially constant and the voltage within prescribed limits, even though the load may change. To meet these load conditions, it is necessary for fuel input to change, for the prime mover input to vary, and for torque on the shaft from the prime mover to change in order that the generator may be kept at constant speed. In addition, the field current to the generator must be adjusted to maintain constant output voltage. Thecontrol system may include a man stationed in the power plant who watches a set of meters on the generator output terminals and makes the necessary adjustments manually. In a modern station, the control system is a servomechanism that senses generator-output conditions and automatically makes the necessary changes in energy input and field current to hold the electrical output within certain specifications..Part 2 More Complicated SystemsIn most situations the load is not directly connected to the generator terminals. More commonly the load is some distance from the generator, requiring a power line connecting them. It is desirable to keep the electric power supply at the load within specifications. However, the controls are near the generator, which may be in another building, perhaps several miles away.If the distance from the generator to the load is considerable, it may be desirable to install transformers at the generator and at the load end, and to transmit the power over a high-voltage line (Fig.1-2). For the same power, the higher-voltage line carries less current, has lower losses for the same wire size, and provides more stable voltage.In some cases an overhead line may be unacceptable. Instead it may be advantageous to use an underground cable. With the power systems talked above, the power supply to the load must be interrupted if, for any reason, any component of the system must be moved from service for maintenance or repair. Additional system load may require more power than the generator can supply. Another generator with its associated transformers and high-voltage line might be added.It can be shown that there are some advantages in making ties between the generators (1) and at the end of the high-voltage lines (2 and 3), as shown in Fig.1-3. This system will operate satisfactorily as long as no trouble develops or no equipmentneeds to be taken out of service.The above system may be vastly improved by the introduction of circuit breakers, which may be opened and closed as needed. Circuit breakers added to the system, Fig.1-4, permit selected piece of equipment to switch out of service without disturbing the remainder of system. With this arrangement any element of the system may be deenergized for maintenance or repair by operation of circuit breakers.Of course, if any piece of equipment is taken out of service, then the total load must be carried by the remaining equipment. Attention must be given to avoid overloads during such circumstances. If possible, outages of equipment are scheduled at times when load requirements are below normal.Fig.1-5 shows a system in which three generators and three loads are tied together by three transmission lines. No circuit breakers are shown in this diagram, although many would be required in such a system.Part 3 Typical System LayoutThe generators, lines, and other equipment which form an electric system are arranged depending on the manner in which load grows in the area and may be rearranged from time to time.However, there are certain plans into which a particular system design may be classified. Three types are illustrated: the radial system, the loop system, and the network system. All of these are shown without the necessary circuit breakers. In each of these systems, a single generator serves four loads.The radial system is shown in Fig.1-6. Here the lines form a “tree” spreading out from the generator. Opening any line results in interruption of power to one or more of the loads.The loop system is illustrated in Fig.1-7. With this arrangement all loads may be served even though one line section is removed from service. In some instances during normal operation, the loop may be open at some point, such as A. In case a line section is to be taken out, the loop is first closed at A and then the line section removed. In this manner no service interruptions occur.Fig.1-8 shows the same loads being served by a network. With this arrangement each load has two or more circuits over which it is fed.Distribution circuits are commonly designed so that they may be classified as radial or loop circuits. The high-voltage transmission lines of most power systems are arranged as network. The interconnection of major power system results in networks made up by many line sections.Part 4 Auxiliary EquipmentCircuit breakers are necessary to deenergize equipment either for normal operation or on the occurrence of short circuits. Circuit breakers must be designed to carry normal-load currents continuously, to withstand the extremely high currents that occur during faults, and to separate contacts and clear a circuit in the presence of fault. Circuit breakers are rated in terms of these duties.When a circuit breaker opens to deenergize a piece of equipment, one side of the circuit breaker usually remains energized, as it is connected to operating equipment. Since it is sometimes necessary to work on the circuit breaker itself, it is also necessary to have means by which the circuit breaker may be completely disconnected from other energized equipment. For this purpose disconnect switches are placed in series with the circuit breakers. By opening these disconnectors, thecircuit breaker may be completely deenergized, permitting work to be carried on in safety.Various instruments are necessary to monitor the operation of the electric power system. Usually each generator, each transformer bank, and each line has its own set of instruments, frequently consisting of voltmeters, ammeters, wattmeters, and varmeters.When a fault occurs on a system, conditions on the system undergo a sudden change. V oltages usually drop and currents increase. These changes are most noticeable in the immediate vicinity of fault. On-line analog computers, commonly called relays, monitor these changes of conditions, make a determination of which breaker should be opened to clear the fault, and energize the trip circuits of those appropriate breakers. With modern equipment, the relay action and breaker opening causes removal of fault within three or four cycles after its initiation.The instruments that show circuit conditions and the relays that protect the circuits are not mounted directly on the power lines but are placed on switchboards in a control house. Instrument transformers are installed on the high-voltage equipment, by means of which it is possible to pass on to the meters and relays representative samples of the conditions on the operating equipment. The primary of a potential transformer is connected directly to the high-voltage equipment. The secondary provides for the instruments and relays a voltage which is a constant fraction of voltage on the operating equipment and is in phase with it;similarly, a current transformer is connected with its primary in the high-current circuit. The secondary winding provides a current that is a known fraction of the power-equipment current and is in phase with it.Bushing potential devices and capacitor potential devices serve the same purpose as potential transformers but usually with less accuracy in regard to ratio and phase angle.中文翻译:电力系统的简介第一部分:最小电力系统一个最小电力系统如图1-1所示,系统包含动力源,原动机,发电机和负载。
电力系统外文英语文献资料
Electric Power SystemElectrical power system refers to remove power and electric parts of the part,It includes substation,power station and distribution. The role of the power grid is connected power plants and users and with the minimum transmission and distribution network disturbance through transport power,with the highest efficiency and possibility will voltage and frequency of the power transmission to the user fixed 。
Grid can be divided into several levels based on the operating voltage transmission system,substructure,transmission system and distribution system, the highest level of voltage transmission system is ZhuWangJia or considered the high power grids. From the two aspects of function and operation,power can be roughly divided into two parts,the transmission system and substation。
The farthest from the maximum output power and the power of the highest voltage grade usually through line to load。
关于电气工程及其自动化电力方面的外文翻译
毕业设计(论文)外文翻译题目。
水电站电气一、二次设计专业电气工程及其自动化(电力)班级。
学生。
指导教师。
2011年2010International Conference on Power System Technology New Challenges to Power System Planning and Operation of Smart Grid Development in China Zhang Ruihua,Du Yumei,Liu YuhongAbstract--The future development trend of electric power gridis smart grid,which includes such features as secure and reliable,efficient and economical,clean and green,flexible andcompatible,open and interactive,integrated and so on.Theconcept and characteristics of smart grid are introduced in thispaper.On the basis of practical national situation, thedevelopment plans of smart grid in china with Chinesecharacteristics are proposed.Smart grid1development in china isbases on information technology,communication technology,computer technology with the high integration with infrastructure of generating,transmission and distributionpower system.Besides,smart grid development in china bringsforward many new challenge and requirements for power systemplanning and operation in9key technologies as below:1.Planning and construction of strong ultra high voltage(UHV)power gridrge-scale thermal power,hydropower and nuclear powerbases integration of power gridrge-scale renewable energy sources2integration of powergrid4.Distributed generation and coordinated development of thegrids of various voltage ratings5.Study on smart grid planning and developing strategy6.Improve the controllability of the power grid based onpower electronics technology.7.Superconductivity,energy storage and other new technologies widely used in power system8.Power system security monitoring,fast simulation,intelligent decision-making and comprehensive defensetechnology9.The application of emergency and restoration control3technology in power systemIn response to the challenge,this paper presents the mainresearch contents,detailed implementation plan and anticipatedgoals of above9key technologies.Some measures and suggestions for power system planning and operation of smartgrid development in China are given in this paper. Index Terms--smart grid,power system planning, powersystem operation,key technologies,large-scale power bases,information and communication technology,computer technology.Zhang Ruihua is with the Institute of Electrical Engineering,ChineseAcademy of Sciences(CAS),Beijing100190,China (E-mail:4ruihuazh@).DU Yumei is with the Institute of Electrical Engineering,ChineseAcademy of Sciences(CAS),Beij ing100190,China Liu Yuhong is with the Institute of Electrical Engineering,ChineseAcademy ofSciences(CAS),Beijing100190,China 978-1-4244-5940-7/10/$26.00.2010IEEEI.INTRODUCTIONWITH the increasing pressure on environmental protection,energy conserving and persistence developsimproves gradually required for society.At the same time,power market-oriented development consistently and providehigher electric energy reliability and quality are required forconsumer_It require that the future smart grid must5can toprovide secure,reliable,clean,high quality power supply,isable to adapt to various of electric power generation,needbeing able to adapt to highly becomemarket-oriented electricpower exchange especially,acting on selfs own being able toadapt to customer especially chooses need,further, improvethe ample power grid assets utilization efficiency andbeneficial result,provide higher quality service. For thispurpose,many countries without exception look upon smartgrid as future development direction of power grid [1-4].6On the basis of present situation and practical condition,the development plans of smart grid in china with Chinesecharacteristics are proposed.The imbalance in the distributionof energy resources and the development of regional economic requires the high efficient development of energyresource in western region to satisfy the electricity demand ofwhole country.Besides,the limitation of environmentalcapacity confines conventional coal-fired thermal power inEast China,which requires a new model of power supply,which will carry out large-scale power flows and balance7between regions[5].The power system condition in different areas of China isvery different.The condition of China's energy and electricityload distribution to determine the long-distance large scalepower transmission will be the direction of the developmentof China's power system_So,this determined the smart grid ofChina with the common characters of smart grid,it with theunique characters of large sending ends,large receiving ends,large power transmission grid[6-9].Smart grid development in china is bases on informationtechnology,communication technology,computer8technologywith the high integration with infrastructure of generating,transmission and distribution power system[10-13]. Smartgrid development in china addresses many new challenge andrequirements for power system planning and operation in9key technical aspects.To response the challenge, the paperpresents main research contents and key technologies in thearea of power system planning and operation,and proposeddetailed implementation procedure and anticipated goals.Finally,some measures and suggestions for power system9planning and operation about China smart grid developmentare given in the paper.II.DEFINITION AND CHARACTERISTICS OF SMART GRID A.The Definition of Smart GridBased on physical power grid,smart grid is a new typepower grid which highly integrates modern advanced information techniques,communication techniques, computerscience and techniques with physical grids.It has manyadvantages,such as improving energy efficiency, reducing theimpact to environment,enhancing the security and reliabilityof power supply and reducing the power loss of the electricitytransmission network and so on.The objectives of smart grid are:fully satisfy customerrequirements for electrical power,optimize resourcesallocation,ensure the security,reliability and economic ofpower supply,satisfy environment protection constraints,guarantee power quality and adapt to power market development.Smart grid can provide customer with reliable,economical,clean and interactive power supply and valueaddedservices.B.The Characteristics of Smart GridSmart grid holds the promise that the power sector can go"green"by not simply reducing the use of dirty powergeneration methods but instead become a system that can takemore aggressive measures to lower greenhouse gas emissionsthrough efficient integration of renewable energy sources.Smart grid that focus on improving demand-side managementfor energy and promoting renewable energy could be atransformational force that redefines the way people viewenergy generation,transmission and consumption, in that suchgrids would encourage active engagement by the broadersociety,not just power sector specialists. Smart grid mainly has features as secure and reliable,efficient and economical,clean and green,flexible andcompatible,open and interactive,integrated and so on[14-15].(1)Secure and Reliable:The power grid is still tomaintain the power supply capacity to the users, rather than alarge area power outage when big disturbances on the powergrid,faults,natural disasters and extreme weather conditions,or man-made damage happen.(2)Efficient and Economical:The power grid can improve the economic benefits through technologicalinnovation,energy efficient management,orderly marketcompetition and related policies.The power grid isin supportof the electricity market and power transactions effectively toachieve the rational allocation of resources and reduce powerlosses and finally to improve the efficiency of energy.(3)Clean and Green:a large-scale of renewable energysources can be fed into the grid which will reduce thepotential impact on the environment.2(4)Optimization:The power grid can improve power supply reliability and security to meet electricity demand indigital age.The optimal cost to provide qualified electricity tothe community.Smart grid can optimize utilizationof assets,reduce investment costs and operation and maintenance costs.Quality of power meets industry standards and consumerneeds.Provide various level of power quality for the range ofneeds.(5)Interactive:interaction and real-time response to thepower market and consumers,which improves service. Maturewholesale market operations in place,well integratednationwide and integrated with reliability coordinators.Retailmarkets flourishing where appropriate.Minimize transmissioncongestion and constraints.(6)Self-healing:The power grid has capabilities such asreal-time&on-line security assessment and analysis,powerfulcontrol system for early warning and prevention control,automatic fault diagnosis,automatic fault isolation and systemself-recovery capability.Self-Healing and adaptive to correctproblems before they become emergencies. Predictive ratherthan reactive,to prevent emergencies ahead rather than solveafter.Resilient to attack and natural disasters with rapidrestoration capabilities.(7)Flexible and Compatible:The power grid can supportcorrect,reasonable integration of renewable energy sourcesand it is suitable for integration of distributed generation andmicro power grid.Besides,it can improve and enhance thefunction of demand side management to achieve the efficientinteraction capability with users.Accommodate all generationand storage options.Very large numbers of diverse distributedgeneration and storage devices deployed to complement thelarge generating plants.(8)Integrated:Unified platform and models are used onthe power grid.It can achieve a high degree of integration andinformation sharing of power grid,and to achieve standard,normative and refined management,which integrates theinfrastructure,processes,devices,information and marketstructure so that energy can be generated, distributed,andconsumed more efficiently and cost effectively. Therebyachieving a more resilient,secure and reliable energy system.Integrated to merge all critical information. III.SMART GRID DEVELOPMENT IN CHINAA.Necessities of Constructing China's Smart grid(1)Rapid growth of economy and society require to construct strong and reliable,efficient and economicalpower gridPower grid is the important infrastructure of energy.Chinese economy will remain high-growth in the future,China's energy and electricity demand over a longer period oftime to maintain a rapid growth in the basic pattern, as well asthe distribution of primary energy resources, unevendistribution and productivity of the basic national conditions,objectively determine the need to implementlong-distance,large-scale transmission,walking across the countryoptimization resource allocation path.Therefore, there is needto construct strong and reliable,efficient andeconomicalpower grid.(2)Global resource environment pressure require to construct resource-saving andenvironmentally-friendlypower gridA smart grid is an inevitable choice for China to addressissues in its power industry and develop alower-carboneconomy.Much of China's power is generated by dirty coalplants.The government has stated that it wants to clean up itsact by boosting renewable power generation to15 percent ofthe total power supply by2020.Chinese smart grid proposalscall for the integration of renewable power sources,includingwind and solar.The current power grid isn't able to efficientlyintegrate intermittent power generation from wind turbines orsolar panels.In order to optimize the energy structure,improve energyefficiency and improve the climate adaptability, the state hasintensified the development on wind,solar and otherrenewable energy.Especially for the large-scale renewableenergy base in the"Three North"area,the local demand is notlarge enough to consume all local electricity,it's necessary totransmit the electricity through long-distancegrid to loadcenter.Generally,due to the intermittence and fluctuation ofrenewable energy,formulation and implementation ofaccurate power generation plan is impossible,which challengethe request the present ability on power acceptance andoptimizing resource allocation.(3)Various generation options require to construct open and transparent,friendly and interactive power gridWith the improving of future Chinese electrification level,power generation enterprises and customers will have higherrequirements for service quality and principles.In order toguarantee the power production and transmission, powergeneration enterprises require power grid to provide reliable,efficient and flexible power integration. Electrical powercustomers will be able to flexibly choose power supply modes,need interaction between power grid to realize high efficienteconomical power utilization,and be capable to senddistributed energy power to power grid in the right time torealize clean and efficient energy utilization.(4)The development of power and relative industry require to construct power grid with leading technologyand equipmentDepending on technology innovation,constructing unifiedstrong smart grid is the development direction of power gridof china.Many advanced technologies and advanced equipment will be applied in constructing smart grid,asubstantial platform can be established for the stable andsecure operation of grids and improve the strength of thegrids'primary systems.It can upgrade the manufacturetechnology of power equipment and control technology ofpower grid.The development of smart grid involved technology and products in many fields of information,communication,power equipment manufacture,intelligent3home electricity machine and so on.It will promote not onlythe development of relative industry but also the technologyinnovation and equipment creation for intelligent building,intelligent home and intelligent transportation.B.Basis oj Constructing China's Smart gridThe basic development goal of power grid is to form asecurity and economical power grid.Constructing smart gridfirstly depend on strong physical power grid.China speedingup the construction the power grid with UHV grid as backbone and subordinate grids coordinated development atall levels.In the technical and institutional, equipmentmanufacturing and project put into practice aspects has laiddown solid basis for the development of smart grid [16].China pays more attention to research and project implementation,many achievements in smart grid have beenaccomplished in China.To be specific,China has alreadyresearch and implementation in following technical aspects:Generation link:In the power generation link includesdistributed generation,renewable energy generation,generatorand power system coordinate operation,and energy-savingoriented dispatching technology andauto-generation control.Transformation link:In the power transformation linkincludes UHV AC and UHV DC transmission,FACTS, digitalsubstation technology,PMU-based W AMS,DMS, stateorientedmaintenance and so on.Distribution and supply link:In the power distributionand supply link includes distribution automation system andfeeder automation system,custom power,auto-metering,Automation measurement technology and electric automobilecharge power station construction and so on. Dispatching link:In the Dispatching link,muchresearchand application have been carried out,such as next generationdispatch technology supporting system,four main dispatchapplication platforms,dispatch technology of energy-savinggeneration,online early warning and coordinated security anddefense technology,integrated model management, massiveinformation process technology,intelligent visualization,dispatch defense technology for extreme disaster. Information building link:In the information buildinglink includes construction of system information collection,load management system,automatic meter readingsystem andother related systems.After promoting of marketing information work for many years,the coverage of users withelectricity collected automatically improves every year,scopeand effect of the system is in gradual expansion, it has playedan active role in the company's marketing, production andsafety management.Many electricity companies are makingthemselves more digital and information-wise, which alsocontributes to smart grid construction.C.Development Goals oJ China's Smart gridThe general development goals of China smart grid isspeed up construction of a strong power grid withUHV powergrid as backbone,coordinated development of power grid atall voltage levels,with information technology, digitization,automation,interactive features into independent innovation,the world's leading strong smart grid.To achieve this goal,the State Grid Corporation of Chinain accordance with unified planning,unified standard,pilotfirst,as a whole to promote the principle of speeding up theconstruction by the UHV AC transmission lines and ±800kV,±1000kV DC transmission lines constitute a UHV backbonepower grid to achieve coordinated development ofthe powergrid at all voltage levels around the power generation,transmission,substations,power distribution, supply,dispatching and other major links and information building,inphases to promote the development of strong smart grid.D.Characteristics of China's Smart Grid Chinese smart grid framework could be different from therest of the world.This is due to the relatively primitivestructure at the distribution ends,the extensive developmentofUHV transmission in recent years,and also the unique assetownership and management structure in China.China's specific national conditions determined the smartgrid of China with the common characters of smart grid,besides,it has own unique characters.These characteristics asbelow:(1)Large sending ends.Based on intensive exploitation oflarge-scale thermal power,hydro power,nuclear power andrenewable energy base,build a strong and smart guideconstructed of UHV power networks as the backbone according to the general requirements of a reliable efficientself-adjustable grid.The strong and smart grid will greatlyoptimize the allocation of resources,improve theservicequality and achieve flexible integration of different sourcesand loads.(2)Large power transmission grid.The Smart Grid initially proposed in the world is to promote intelligence andautomation for distribution system.The shortage of electricpower supply in China is still a challenge,so construction fora strong national transmission networks to realize the electricpower transmission from the west to the east and the mutualsupply between the south and the north is still the main task.In China,to develop a smart transmission grid should beranked in a priority.Smart transmission grid includes both theconstruction of a strong UHV grid and the development of thesmart dispatch and control technologies.(3)Large receiving ends.In China,the electricity pricewas not opened to follow the electricity market,so the roomfor demand side management and costumer participation islimited.Therefore Smart Grid in China has a much differentconnotation compared with that used in west countries.The smart grid with Chinese characteristics are the meansand modes to realize grid asset efficient management,enlargegrids'capability to serve both electricity producers andelectricity users,make rational developing planning strategiesand optimize system operation under the conditions ofcontinuously lowering costs,improving efficiency andbenefits and bettering the reliability and availability of thewhole power systems,with UHV power grid as backbone andthe coordinated development of the power grid of various4voltage levels and in combination of advanced information,communication and control technologies and the advancedmanagerial philosophy[17-18].IV.NEW CHALLENGES TO POWER SYSTEM PLANNING OF SMART GRID DEVELOPMENT IN CHINAThe development of smart grid in china bring forward many new challenges and requirements for power systemplanning in5key technical aspects,which are analyzed in thissection,detailed implementation plan and anticipated goals areproposed.5key technical aspects are as follows: A.Planning and Construction of Strong UHV Power GridResearch content:Construct the UHV power grid structure to meet the requirements of smart grid development.The structure must have strong adaptive ability, highreliability and security,strong ability to resistfailure for theintegration of the multifarious large-scale power generation,and can provides a flexible and easy network infrastructureconditions for the stability control system.Study of the smartpower grid structure with the flexible energy exchange abilityand the operating conditions adjust ability that can achieve theeffective management and efficient use of resources byadjusting power network,and can continuously improve theeconomic benefits of the power grid.Study the HVDC planning for the receiving-end of the power system,propose the configuration principles for theintelligent dynamic reactive power compensation devices andthe planning indices of the HVDC that can improve thevoltage stability in the multi-infeed HVDC power system.Forecasting the load,the installed capacity and the power flowscale on the base of the analysis to economic and socialdevelopment and the energy resources distribution in ourcountry.Demonstrate the major technical problems thatshould be considered during the construction process of thestrong and reasonable UHV network structure.Study thevarious factors which will affect the developmentof UHVnetwork with the current technology and the current development status of the power network. Implementation Plan:The first stage will focus mainly onthe UHV power development strategy,and the rationalstructure of UHV power network.The second stage will fullyresearch the way of the large power base integration to UHVpower network,the main factors which will affect the multiinfeedHVDC power system,the planning for the receivingendof multi-infeed HVDC power transmission system,and other pivotal technologies.The third stage will fully build thestrong UHV network that can meet the demand of thesmartgrid.Targets:Present the particular configuration of the UHVnetwork that can meet the special needs of the future smartgrid.Guide the coordinated and sustainable development tothe power grid in our country.rge-Scale Ordinary Power Bases Integration of PowerSystemResearch content:Smart grid development in china require to study on security and stability,control measures andintegration patterns of large-scale hydropower or thermalpower bases connecting to power systems.Study the securitystability and control technology of the HVDC islandedsending mode.Study coordinated control strategy of AC/DCsystem to improve system stability and the interactionsbetween the integrated huge wind farms and the power grid.The factors which impact on large power supplies integrationof power system are analyzed.Implementation Plan:The first stage will focus mainly oncompare the various integration patterns of large powersupplies to power grid.The second stage will fully researchcoordinated control strategy of AC/DC system to improvesystem stability.The third stage will propose integrationpatterns and control measures of large power supplies topower grid satisfied to the requirement of smart grid.Targets:Propose the principles optimized integrationpatterns of large power supply integration to power grid.Enhance generators and power grid coordinate operation,toensure power system safely and economical operation.rge-Scale Renewable Energy Sources Integration ofPower SystemResearch content:Study and summarize the electricityproduction features of various renewable energy sources(suchas wind power,photovoltaic power generation). Analyze the influence,the interaction and the technologiesthat must be considered when the large-scale renewableenergy production with different characteristics integration tothe power grid.Implementation Plan:The first stage will focus mainly onthe influence when the large-scale renewable energy production with different characteristics integration to thepower grid.The second stage will fully study the interactionand the technologies that must be considered when the largescalerenewable energy production integration to the powergrid.The third stage will study the reasonable delivery scaleof the renewable energy base and the reasonable deliveryproportion of the renewable energy and the conventionalenergy and other storage systems such as pumped storagedevice and flywheel energy storage device. Targets:propose the system planning methods and thetechnologies that can meet the demands when the largerenewable energy integration to the power grid.D.Distributed Generation and Coordinated Development ofTransmission and Distribution NetworkResearch content:Study the operating characteristics ofdifferent distributed power generation and power supplysystem,study the interaction mechanism between the distributed power supply system and the power grid. Study thecoordinated development at all levels of power transmissionand distribution under the smart grid goals,and propose thedesign principles about the coordinated development of the5power transmission and distribution planning at all levels;Study the planning method for the coordinated developmentof UHV IEHV power grid;study the planningprinciples forregional power grid that are adapt to the development ofUHVpower grid;study the influence of HVDC powerin-feed andthe development of regional EHV power grid;study theprinciples and the time of looping-off for UHV IEHV electromagnetic loop;study the coordinated planning forUHV IEHV power grid that can improve grid stability andinhibit the short circuit current. Implementation Plan:The first stage will focus mainly onthe analysis methods for the distributed power supply systemperformance,and the coordinated development of the powertransmission and distribution at all levels.The second stagewill fully research the interaction mechanism between thedistributed power supply system and the power grid, and theplanning method for the coordinated development of UHV/EHV power grid.The third stage will propose the standardsand test specifications for the distributed power gridconnectionrunning.Targets:Propose the planning methods for the coordinateddevelopment of the transmission and distribution network,optimize the network resources and improve the safety and。
毕业设计毕业论文电气工程及其自动化外文翻译中英文对照
毕业设计毕业论文电气工程及其自动化外文翻译中英文对照电气工程及其自动化外文翻译中英文对照一、引言电气工程及其自动化是一门涉及电力系统、电子技术、自动控制和信息技术等领域的综合学科。
本文将翻译一篇关于电气工程及其自动化的外文文献,并提供中英文对照。
二、文献翻译原文标题:Electric Engineering and Its Automation作者:John Smith出版日期:2020年摘要:本文介绍了电气工程及其自动化的基本概念和发展趋势。
首先,介绍了电气工程的定义和范围。
其次,探讨了电气工程在能源领域的应用,包括电力系统的设计和运行。
然后,介绍了电气工程在电子技术领域的重要性,包括电子设备的设计和制造。
最后,讨论了电气工程与自动控制和信息技术的结合,以及其在工业自动化和智能化领域的应用。
1. 介绍电气工程是一门研究电力系统和电子技术的学科,涉及发电、输电、配电和用电等方面。
电气工程的发展与电力工业的发展密切相关。
随着电力需求的增长和电子技术的进步,电气工程的重要性日益凸显。
2. 电气工程在能源领域的应用电气工程在能源领域的应用主要包括电力系统的设计和运行。
电力系统是由发电厂、输电线路、变电站和配电网络等组成的。
电气工程师负责设计和维护这些设施,以确保电力的可靠供应。
3. 电气工程在电子技术领域的重要性电气工程在电子技术领域的重要性体现在电子设备的设计和制造上。
电子设备包括电脑、手机、电视等消费电子产品,以及工业自动化设备等。
电气工程师需要掌握电子电路设计和数字信号处理等技术,以开发出高性能的电子设备。
4. 电气工程与自动控制和信息技术的结合电气工程与自动控制和信息技术的结合是电气工程及其自动化的核心内容。
自动控制技术可以应用于电力系统的运行和电子设备的控制,以提高系统的稳定性和效率。
信息技术则可以用于数据采集、处理和传输,实现对电力系统和电子设备的远程监控和管理。
5. 电气工程在工业自动化和智能化领域的应用电气工程在工业自动化和智能化领域的应用越来越广泛。
电力系统毕业论文中英文外文文献翻译
电力系统电力系统介绍随着电力工业的增长,与用于生成和处理当今大规模电能消费的电力生产、传输、分配系统相关的经济、工程问题也随之增多。
这些系统构成了一个完整的电力系统。
应该着重提到的是生成电能的工业,它与众不同之处在于其产品应按顾客要求即需即用。
生成电的能源以煤、石油,或水库和湖泊中水的形式储存起来,以备将来所有需。
但这并不会降低用户对发电机容量的需求。
显然,对电力系统而言服务的连续性至关重要。
没有哪种服务能完全避免可能出现的失误,而系统的成本明显依赖于其稳定性。
因此,必须在稳定性与成本之间找到平衡点,而最终的选择应是负载大小、特点、可能出现中断的原因、用户要求等的综合体现。
然而,网络可靠性的增加是通过应用一定数量的生成单元和在发电站港湾各分区间以及在国内、国际电网传输线路中使用自动断路器得以实现的。
事实上大型系统包括众多的发电站和由高容量传输线路连接的负载。
这样,在不中断总体服务的前提下可以停止单个发电单元或一套输电线路的运作。
当今生成和传输电力最普遍的系统是三相系统。
相对于其他交流系统而言,它具有简便、节能的优点。
尤其是在特定导体间电压、传输功率、传输距离和线耗的情况下,三相系统所需铜或铝仅为单相系统的75%。
三相系统另一个重要优点是三相电机比单相电机效率更高。
大规模电力生产的能源有:1.从常规燃料(煤、石油或天然气)、城市废料燃烧或核燃料应用中得到的蒸汽;2.水;3.石油中的柴油动力。
其他可能的能源有太阳能、风能、潮汐能等,但没有一种超越了试点发电站阶段。
在大型蒸汽发电站中,蒸汽中的热能通过涡轮轮转换为功。
涡轮必须包括安装在轴承上并封闭于汽缸中的轴或转子。
转子由汽缸四周喷嘴喷射出的蒸汽流带动而平衡地转动。
蒸汽流撞击轴上的叶片。
中央电站采用冷凝涡轮,即蒸汽在离开涡轮后会通过一冷凝器。
冷凝器通过其导管中大量冷水的循环来达到冷凝的效果,从而提高蒸汽的膨胀率、后继效率及涡轮的输出功率。
而涡轮则直接与大型发电机相连。
电气 自动化 外文翻译 外文文献 英文文献
外文出处:Farhadi, A. (2008). Modeling, simulation, and reduction of conducted electromagnetic interference due to a pwm buck type switching power supply. Harmonics and Quality of Power, 2008. ICHQP 2008. 13th International Conference on, 1 - 6.Modeling, Simulation, and Reduction of Conducted Electromagnetic Interference Due to a PWM Buck Type Switching Power Supply IA. FarhadiAbstract:Undesired generation of radiated or conducted energy in electrical systems is called Electromagnetic Interference (EMI). High speed switching frequency in power electronics converters especially in switching power supplies improves efficiency but leads to EMI. Different kind of conducted interference, EMI regulations and conducted EMI measurement are introduced in this paper. Compliancy with national or international regulation is called Electromagnetic Compatibility (EMC). Power electronic systems producers must regard EMC. Modeling and simulation is the first step of EMC evaluation. EMI simulation results due to a PWM Buck type switching power supply are presented in this paper. To improve EMC, some techniques are introduced and their effectiveness proved by simulation.Index Terms:Conducted, EMC, EMI, LISN, Switching SupplyI. INTRODUCTIONFAST semiconductors make it possible to have high speed and high frequency switching in power electronics []1. High speed switching causes weight and volume reduction of equipment, but some unwanted effects such as radio frequency interference appeared []2. Compliance with electromagnetic compatibility (EMC) regulations is necessary for producers to present their products to the markets. It is important to take EMC aspects already in design phase []3. Modeling and simulation is the most effective tool to analyze EMC consideration before developing the products. A lot of the previous studies concerned the low frequency analysis of power electronics components []4[]5. Different types of power electronics converters are capable to be considered as source of EMI. They could propagate the EMI in both radiated and conducted forms. Line Impedance Stabilization Network (LISN) is required for measurement and calculation of conducted interference level []6. Interference spectrum at the output of LISN is introduced as the EMC evaluation criterion []7[]8. National or international regulations are the references forthe evaluation of equipment in point of view of EMC []7[]8.II. SOURCE, PATH AND VICTIM OF EMIUndesired voltage or current is called interference and their cause is called interference source. In this paper a high-speed switching power supply is the source of interference.Interference propagated by radiation in area around of an interference source or by conduction through common cabling or wiring connections. In this study conducted emission is considered only. Equipment such as computers, receivers, amplifiers, industrial controllers, etc that are exposed to interference corruption are called victims. The common connections of elements, source lines and cabling provide paths for conducted noise or interference. Electromagnetic conducted interference has two components as differential mode and common mode []9.A. Differential mode conducted interferenceThis mode is related to the noise that is imposed between different lines of a test circuit by a noise source. Related current path is shown in Fig. 1 []9. The interference source, path impedances, differential mode current and load impedance are also shown in Fig. 1.B. Common mode conducted interferenceCommon mode noise or interference could appear and impose between the lines, cables or connections and common ground. Any leakage current between load and common ground couldbe modeled by interference voltage source.Fig. 2 demonstrates the common mode interference source, common mode currents Iandcm1 and the related current paths[]9.The power electronics converters perform as noise source Icm2between lines of the supply network. In this study differential mode of conducted interference is particularly important and discussion will be continued considering this mode only.III. ELECTROMAGNETIC COMPATIBILITY REGULATIONS Application of electrical equipment especially static power electronic converters in different equipment is increasing more and more. As mentioned before, power electronics converters are considered as an important source of electromagnetic interference and have corrupting effects on the electric networks []2. High level of pollution resulting from various disturbances reduces the quality of power in electric networks. On the other side some residential, commercial and especially medical consumers are so sensitive to power system disturbances including voltage and frequency variations. The best solution to reduce corruption and improve power quality is complying national or international EMC regulations. CISPR, IEC, FCC and VDE are among the most famous organizations from Europe, USA and Germany who are responsible for determining and publishing the most important EMC regulations. IEC and VDE requirement and limitations on conducted emission are shown in Fig. 3 and Fig. 4 []7[]9.For different groups of consumers different classes of regulations could be complied. Class Afor common consumers and class B with more hard limitations for special consumers are separated in Fig. 3 and Fig. 4. Frequency range of limitation is different for IEC and VDE that are 150 kHz up to 30 MHz and 10 kHz up to 30 MHz respectively. Compliance of regulations is evaluated by comparison of measured or calculated conducted interference level in the mentioned frequency range with the stated requirements in regulations. In united European community compliance of regulation is mandatory and products must have certified label to show covering of requirements []8.IV. ELECTROMAGNETIC CONDUCTED INTERFERENCE MEASUREMENTA. Line Impedance Stabilization Network (LISN)1-Providing a low impedance path to transfer power from source to power electronics converter and load.2-Providing a low impedance path from interference source, here power electronics converter, to measurement port.Variation of LISN impedance versus frequency with the mentioned topology is presented inFig. 7. LISN has stabilized impedance in the range of conducted EMI measurement []7.Variation of level of signal at the output of LISN versus frequency is the spectrum of interference. The electromagnetic compatibility of a system can be evaluated by comparison of its interference spectrum with the standard limitations. The level of signal at the output of LISN in frequency range 10 kHz up to 30 MHz or 150 kHz up to 30 MHz is criterion of compatibility and should be under the standard limitations. In practical situations, the LISN output is connected to a spectrum analyzer and interference measurement is carried out. But for modeling and simulation purposes, the LISN output spectrum is calculated using appropriate software.基于压降型PWM开关电源的建模、仿真和减少传导性电磁干扰摘要:电子设备之中杂乱的辐射或者能量叫做电磁干扰(EMI)。
3-电气工程及其自动化专业 外文文献 英文文献 外文翻译
3-电气工程及其自动化专业外文文献英文文献外文翻译1、外文原文(复印件)A: Fundamentals of Single-chip MicrocomputerThe single-chip microcomputer is the culmination of both the development of the digital computer and the integrated circuit arguably the tow most significant inventions of the 20th century [1].These tow types of architecture are found in single-chip microcomputer. Some employ the split program/data memory of the Harvard architecture, shown in Fig.3-5A-1, others follow the philosophy, widely adapted for general-purpose computers and microprocessors, of making no logical distinction between program and data memory as in the Princeton architecture, shown in Fig.3-5A-2.In general terms a single-chip microcomputer is characterized by the incorporation of all the units of a computer into a single device, as shown in Fig3-5A-3.ProgramInput& memoryOutputCPU unitDatamemoryFig.3-5A-1 A Harvard typeInput&Output CPU memoryunitFig.3-5A-2. A conventional Princeton computerExternal Timer/ System Timing Counter clock componentsSerial I/OReset ROMPrarallelI/OInterrupts RAMCPUPowerFig3-5A-3. Principal features of a microcomputerRead only memory (ROM).ROM is usually for the permanent,non-volatile storage of an applications program .Many microcomputers and microcontrollers are intended for high-volume applications and hence the economical manufacture of the devices requires that the contents of the program memory be committed permanently during the manufacture of chips . Clearly, this implies a rigorous approach to ROM code development since changes cannot be made after manufacture .This development process may involve emulation using a sophisticated development system with a hardware emulation capability as well as the use of powerful software tools.Some manufacturers provide additional ROM options by including in their range devices with (or intended for use with) user programmablememory. The simplest of these is usually device which can operate in a microprocessor mode by using some of the input/output lines as an address and data bus for accessing external memory. This type of device can behave functionally as the single chip microcomputer from which itis derived albeit with restricted I/O and a modified external circuit. The use of these ROMlessdevices is common even in production circuits where the volume does not justify the development costs of custom on-chip ROM[2];there canstill be a significant saving in I/O and other chips compared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with 'piggy-back' EPROM(Erasable programmable ROM )sockets or devices with EPROM instead of ROM 。
电气工程及其自动化 外文翻译 外文文献 英文文献 短路电流
电气工程及其自动化外文翻译外文文献英文文献短路电流Short-circuit current1 Terms and DefinitionsThe following terms and definitions correspond largely to those defined in IEC 60909. Refer to this standard for all terms not used in this book.The terms short circuit and ground fault describe faults in the isolation ofoperational equipment which occur when live parts are shunted out asa result. , Causes:1. Overtemperatures due to excessively high overcurrents.2. Disruptive discharges due to overvoltages.3. Arcing due to moisture together with impure air, especially on insulators. , Effects:1. Interruption of power supply.2. Destruction of system components.3. Development of unacceptable mechanical and thermal stresses in electrical operational equipment., Short circuit:According to IEC 60 909, a short circuit is the accidental or intentional conductive connection through a relatively low resistance orimpedance between two or more points of a circuit which are normally at different potentials., Short circuit current:According to IEC 60 909, a short circuit current results from a short circuit in an electrical network.It is necessary to differentiate here between the short circuit current at the position of the short circuit and the transferred short circuit currents in the network branches., Initial symmetrical short circuit current:This is the effective value of the symmetrical short circuit current at the moment at which the short circuit arises, when the short circuit impedance has its value from the time zero., Initial symmetrical short circuit apparent power:The short circuit power represents a fictitious parameter. During the planning of networks, the short circuit power is a suitable characteristic number. , Peak short circuit current:The largest possible momentary value of the short circuit occurring. , Steady state short circuit current:Effective value of the initial symmetrical short circuit current remaining after the decay of all transient phenomena., DC aperiodic component:Average value of the upper and lower envelope curve of the short circuit current, which slowly decays to zero., Symmetrical breaking current:Effective value of the short circuit current which flows through the contact switch at the time of the first contact separation., Equivalent voltage source:The voltage at the position of the short circuit, which is transferred to the positive-sequence system as the only effective voltage and is used for the calculation of the short circuit currents., Superposition method:The superposition method considers the previous load of the network before the occurrence of the short circuit. It is necessary to know the load flow and the setting of the transformer step switch., Voltage factor:Ratio between the equivalent voltage source and the network voltage Un,divided by 3., Equivalent electrical circuit:Model for the description of the network by an equivalent circuit. , Far-from-generator short circuit:The value of the symmetrical AC periodic component remains essentially constant., Near-to-generator short circuit:The value of the symmetrical AC periodic component does not remain constant. The synchronous machine first delivers an initial symmetrical short circuit current which is larger than twice the rated current of the synchronous machine. , Positive-sequence short circuit impedance:The impedance of the positive-sequence system as seen from the position of theshort circuit., Negative-sequence short circuit impedance:The impedance of the negative-sequence system as seen from the position ofthe short circuit., Zero-sequence short circuit impedanceThe impedance of the zero-sequence system as seen from the position of theshort circuit. Three times the value of the neutral point to ground impedanceoccurs here., Short circuit impedance:Impedance required for calculation of the short circuit currents at the positionof the short circuit. p•••1.2 Short circuit path in the positive-sequence systemFor the same external conductor voltages, a three-pole short circuit allows three currents of the same magnitude to develop between the three conductors. It is therefor only necessary to consider one conductor in further calculations. Depending on the distance from the position of the short circuit from the generator, here it is necessary to consider near-to-generator andfar-from-generator short circuits separately. For far-from-generator and near-to-generator short circuits, the short circuit path can be represented by a mesh diagram with AC voltage source, reactances X and resistances R (Figure 1.2). Here, X and R replace all components such as cables,conductors, transformers, generators and motors.Fig. 1.2: Equivalent circuit of the short circuit current path in the positive-sequence systemThe following differential equation can be used to describe theshort circuit processwhere w is the phase angle at the point in time of the short circuit. This assume that the current before S closes (short circuit) is zero. The inhomogeneous first order differential equation can be solved by determining the homogeneous solution ik and a particular solution i?k.The homogeneous solution, with the time constant g = L/R, solution yields:For the particular solution, we obtain:The total short circuit current is composed of both components:The phase angle of the short circuit current (short circuit angle)is then, in accordance with the above equation,For the far-from-generator short circuit, the short circuit current is therefore made up of a constant AC periodic component and the decaying DC aperiodic component. From the simplified calculations, we can now reach the following conclusions:, The short circuit current always has a decaying DC aperiodic component inaddition to the stationary AC periodic component., The magnitude of the short circuit current depends on theoperating angle ofthe current. It reaches a maximum at c = 90 (purely inductive load). Thiscase serves as the basis for further calculations., .The short circuit current is always inductive.1.4 Methods of short circuit calculationThe equivalent voltage source will be introduced here as the only effective voltage of the generators or network inputs for thecalculation of short circuit currents. The internal voltages of generators or network inputs are short circuited, and at the position ofthe short circuit (fault position) the value ( is used as the only effective voltage (Figure 1.4)., The voltage factor c [5] considers (Table 1.1):, The different voltage values, depending on time and position, The step changes of the transformer switch, That the loads and capacitances in the calculation of the equivalentvoltage source can be neglected, The subtransient behavior of generators and motors, This method assumes the following conditions:, The passive loads and conductor capacitances can be neglected , The step setting of the transformers do not have to be considered , The excitation of the generators do not have to be considered , The time and position dependence of the previous load (loading state) ofthe network does not have to be consideredFig. 1.4: Network circuit with equivalent voltage sourcea) three-phase network, b) equivalent circuit in positive sequencesystem1.4.2 Superposition methodThe superposition method is an exact method for the calculation of the short circuit currents. The method consists of three steps. The voltage ratios and the loading condition of the network must be known before the occurrence of the short circuit. In the first step the currents, voltages and the internal voltages for steady-state operation before onset of the short circuit are calculated (Figure 1.5b). The calculation considers the impedances, power supply feeders and node loads of the active elements. In the second step the voltage applied to the fault location before the occurrence of the short circuit and the current distribution at the fault location are determined with a negative sign (Figure 1.5c). This voltage source is the only voltage source in the network. The internal voltages are short-circuited. In the third step both conditions are superimposed. We then obtain zero voltage at the fault location. The superposition of the currents also leads to the value zero. The disadvantage of this method is that the steady-state condition must be specified. The data for the network (effective andreactive power, node voltages and the step settings of the transformers) are often difficult to determine. The question also arises, which operating state leads to the greatest short circuit current. Figure 1.5 illustrates the procedure for the superposition method.Fig. 1.5: Principle of the superposition methoda) undisturbed operation, b) operating voltage at the faultlocation, c) superposition of a) and b)1.4.3 Transient calculationWith the transient method the individual operating equipment and, as a result, the entire network are represented by a system of differential equations. The calculation is very tedious. The method with the equivalent voltage source is a simplification relative to the other methods. Since 1988, it has been standardized internationally in IEC 60 909. The calculation is independent of a current operational state. Inthisbook, we will therefore deal with and discuss the method with the equivalent voltage source.1.5 Calculating with reference variablesThere are several methods for performing short circuit calculations with absolute and reference impedance values. A few are summarized here and examples are calculated for comparison. To define the relative values, there are two possible reference variables.For the characterization of electrotechnical relationships we require the four parameters:, Voltage U in V, Current I in A, Impedance Z in W, Apparent power S in VA.Three methods can be used to calculate the short circuit current:1. The Ohm system: Units: kV, kA, V, MVA2.The pu system:This method is used predominantly for electrical machines; allfour parameters u, i, z and s are given as per unit (unit = 1). The reference valueis 100 MVA. The two reference variables for this system are UB and SB.Example: The reactances of a synchronous machine Xd, X?d, X?d are givenin pu or in % pu, multiplied by 100 %.3.The %/MVA system:This system is especially well suited for thefastdetermination of short circuit impedances. As formal unit only the % symbol isadd.短路电流1 术语和定义以下术语和定义对应IEC 标准60 909。
电气工程及其自动化 英语
电气工程及其自动化英语Electric Engineering and its AutomationElectric engineering is a branch of engineering that is concerned with the study, design, application, and maintenance of electrical systems. These systems includepower generation, transmission, distribution, and utilization. Electric engineering plays a critical role in the development and improvement of our daily lives, as it is responsible for the functionality and optimization of machines, devices, and systems that we rely on every day.One of the key developments in electric engineering in recent years is automation. Automation has revolutionized industries across the globe by increasing efficiency, reducing labor costs, and improving safety. Automation allows for thecontrol and operation of machines or systems without human intervention, thereby increasing the accuracy, speed, and reliability of processes.An example of automation in electric engineering is the useof programmable logic controllers (PLCs). PLCs are electronic devices that can be programmed to control industrialprocesses such as conveyor systems, robotic arms, andassembly lines. They can automate complex processes,improving efficiency, accuracy, and reducing the risk of errors.Another example is the use of smart grids. Smart grids useadvanced technologies to automate the distribution of electricity. They allow for two-way communication between the utility and the customer, enabling real-time monitoring and control of electricity usage, reducing consumption, and improving energy efficiency.The automation of electric engineering has also increased the availability of data analysis, allowing for better decision making through the use of mathematical modeling and simulation. This has led to the development of newtechnologies and the improvement of existing ones.In conclusion, electric engineering and its automation have become essential components of modern living. From power generation to distribution, from manufacturing to transportation, electric engineering plays a critical role in our everyday lives. With the continued development of automation technologies and their integration into electric engineering, we can expect further improvements to efficiency, safety, and sustainability.。
电气化专业外文资料翻译
英文原文:Control theory and electricity grids theory is the electrical engineering and automation major foundation, the power electronic technology, computer technology is its main technical means, also contains a systems analysis, system design, system development and system management and decision-making, etc research field.The professional and some feature that weak electricity combining, electrical and electronic technology to combine together, software and hardware, combining with interdisciplinary nature, electric power, electronics, control, computer multi-discipline, give graduates have strong adaptability, is "the broad caliber" professional.Electrical engineering and automation to the examinee has a strong attraction, belongs to the popular major, the university entrance exam to admit fractional line often than other professional direction high, killing this lot are the main reasons:(1) the employment easy, working environment is good, the high income;(2) the name of students listen, professional content attractive;Social propaganda and public opinion guide to its advantage.The professional direction has a very good prospects for development, the research results easier to reality and product shifts, with considerable benefits.His creative thinking attracts many examinee, here is really good place to display their talent.But given the form of domestic now, examinee in enter oneself for an examination the professional when should pay attention to the following two points: (1) fully consider their interests.Maybe he could not for the sense of direction interested, but many people say, so oneself "interest".The following development is very harmful. After all, the interest is the best teacher.(2) measure their comprehensive quality.Electrical engineering and automation need strong knowledge of mathematics, physics foundation, strong language comprehensive ability, can grasp and flexible for future use professional knowledge for preparation.The professional direction of the personnel needs, but although large selection of many people, if not very strong comprehensive quality, it is difficult to get out in the crowd, outstanding achievements.Perhaps this for many bosom the examinee of lofty ambition it is unacceptable.Of course, here said the two also and whether it is feasible to the pursuit of individual students about, if a person is limited to pursuit a better job, this major is a good choice.But, if want to make breakthrough technology innovation or based on personal contribution strength as well as hard work, on the basis of the pie is never unprovoked fell from the sky.Because this major research scope, the application prospect of professional quality, graduates are relatively high, therefore employment situation very well.Our country is very need the professional direction of the talent, small to a family, to the whole society, are inseparable from these professional work. Normally, students can choose state-owned quality technical supervision department, research institute, industrial mining enterprises etc;Can also be some foreign investment, private enterprise, treatment of course is considerable.If it is strong enough, and students' ability in during study accumulated better research achievements, can completely his business, rush piece of the sky belongs.It should bepointed out that, because in the professional direction of the overseas research, so bringing preceded us if they want to have further development, establish themselves in the leading position in domestic this direction, to go abroad for further study is a good choice.中文译文:控制理论和电力网理论是电气工程及其自动化专业的基础,电力电子技术,计算机技术是它的主要技术手段,也包含了系统分析,系统设计,系统开发以及系统管理与决策等研究领域。
电气工程及其自动化电压波动论文中英文资料外文翻译文献
中英文资料外文翻译文献原文:A SPECIAL PROTECTION SCHEME FOR VOLTAGESTABILITY PREVENTIONAbstractVoltage instability is closely related to the maximum load-ability of a transmission network. The energy flows on the transmission system depend on the network topology, generation and loads, and on the availability of sources that can generate reactive power. One of the methods used for this purpose is the Voltage Instability Predictor (VIP). This relay measures voltages at a substation bus and currents in the circuit connected to the bus. From these measurements, it estimates the Thévenin’s equivalent of the network feeding the substation and the impedance of the load being supplied from the substation. This paper describes an extension to the VIP technique in which measurements from adjoining system buses and anticipated change of load are taken into consideration as well.Keywords: Maximum load ability; Voltage instability; VIP algorithm.1.IntroductionDeregulation has forced electric utilities to make better use of the available transmission facilities of their power system. This has resulted in increased power transfers, reduced transmission margins and diminished voltage security margins.To operate a power system with an adequate security margin, it is essential to estimate the maximum permissible loading of the system using information about the current operation point. The maximum loading of a system is not a fixed quantity but depends on various factors, such as network topology, availability of reactive power reserves and their location etc. Determining the maximum permissible loading, within the voltage stability limit, has become a very important issue in power system operation and planning studies. The conventional P-V or V- Q curves are usually used as a tool for assessing voltage stability and hence for finding the maximum loading at the verge of voltage collapse [1]. These curves are generated by running a large number of load flow cases using, conventional methods. While such procedures can be automated, they are time-consuming and do not readily provide information useful in gaining insight into the cause of stability problems [2].To overcome the above disadvantages several techniques have been proposed in the literature, such as bifurication theory [3], energy method [4], eigen value method [5],multiple load flow solutions method [6] etc.Reference [7] proposed a simple method, which does not require off-line simulation and training. The Voltage Indicator Predictor (VIP) method in [7] is based on local measurements (voltage and current) and produces an estimate of the strength / weakness of the transmission system connected to the bus, and compares it with the local demand. The closer the local demand is to the estimated transmission capacity, the more imminent is the voltage instability. The main disadvantage of this method is in the estimation of the Thévenin’s equivalent, which is obtained from two measurements at different times. For a more exact estimation, one requires two different load measurements.This paper proposes an algorithm to improve the robustness of the VIP algorithm by including additional measurements from surrounding load buses and also taking into consideration local load changes at neighboring buses.2. Proposed MethodologyThe VIP algorithm proposed in this paper uses voltage and current measurements on the load buses and assumes that the impedance of interconnecting lines (12Z ,13Z ) are known, as shown in (Figure 1). The current flowing from the generator bus to the load bus is used to estimate Thévenin’s equivalent for the system in that direction. Similarly the current flowing from other load bus (Figure 2) is used to estimate Thévenin’s equivalent from other direction. This results in following equations (Figure 3). Note that the current coming from the second load bus over the transmission line was kept out of estimation in original (VIP) algorithm.)()()(111112211111----=-+th th th L Z E Z V Z Z V [1] )()()(122112112122----=-+th th th L Z E Z V Z Z V [2] 1111111)()(E th th th I Z V Z E =--- [3] 2122122)()(E th th th I Z V Z E =--- [4] Where 1E I and 2E I are currents coming from Th évenin buses no.1 and 2. Equation (1)-(4) can be combined into a matrix form:⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡---++---++-------------121211111212112121-12111121111211000000th th th th th th L th th L Z Z Z Z Z Z Z Z Z Z Z Z Z Z *=⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡2121th th E E V V ⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡2100E E I I [5] Using the first 2 rows in the system Equations (1)-(4), the voltage on buses number 1 and 2 can be found as shown in Equation (6) below. From Equation (6) wecan see that the voltage is a function of impedances. Note that the method assumes that all Thévenin’s parameters are constant at the time of estimation.⎥⎥⎦⎤⎢⎢⎣⎡⎥⎥⎦⎤⎢⎢⎣⎡++--++=⎥⎦⎤⎢⎣⎡-----------12211111121212112112112111121*th th th th th L th L Z E Z E Z Z Z Z Z Z Z Z V V [6] Where, 111-=L Z y 11212-=Z y and 122-=L Z yThe system equivalent seen from bus no.1 is shown in Figure 3. Figure 4(a) shows the relationship between load admittances (1y and 2y ) and voltage at bus no.1. Power delivered to bus no.1 is (1S ) and it is a function of (1L Z ,2L Z ).1211*L y V S = [7]Equation 7 is plotted in figure 4 (b) as a ‘landscape’ and the maximum loading point depends on where the system trajectory ‘goes over the hill’.Fig. 1. 3-Bus system connections Fig. 2. 1-Bus modelFig. 3. System equivalent as seen by the proposed VIP relay on bus #1 (2-bus model)(a)Voltage Profile (b) Power ProfileFig. 4. Voltage and power profiles for bus #12.1. On-Line Tracking of Thévenin’s ParametersThévenin’s parameters are the main factors that decide the maximum loading of the load bus and hence we can detect the voltage collapse. In Figure3, th E can be expressed by the following equation:I Z V E th load th += [8]V and I are directly available from measurements at the local bus. Equation (8) can be expressed in the matrix form as shown below.⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡--⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡=⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡000010000001)()(00..r i i r th th th th i r I I I I X R i E r E V V [9] B= A X [10] The unknown parameters can be estimated from the following equation:B A AX A T T = [11] Note that all of the above quantities are functions of time and are calculated on a sliding window of discrete data samples of finite, preferably short length. There are additional requirements to make the estimation feasible:• There must be a significant change in load impedance in the data window of at least two set of Measurements.• For small changes in Thévenin’s parameters within a particular data window, the algorithm can estimate properly but if a sudden large change occurs then the process of estimation is postponed until the next data window comes in.• The monitoring device based on the above principle can be used to impose a limit on the loading at each bus, and sheds load when the limit is exceeded. It can also be used to enhance existing voltage controllers. Coordinated control canalso be obtained if communication is available.Once we have the time sequence of voltage and current we can estimate unknowns by using parameter estimation algorithms, such as Ka lm an Filtering approach described [6].stability margin (VSM) due to impedances can be expressed as (Z VSM ); where subscript z denotes the impedance.Therefore we have: Load thev Load Z Z Z Z VSM -= [12] The above equation assumes that both load impedances (1Z , 2Z ) are decreasing at a steady rate, so the power delivered to bus 1 will increase according to Equation(7). However once it reaches the point of collapse power starts to decrease again.Now assume that both loads are functions of time. The maximum critical loading point is then given by Equation(13):011==dtds S Critical [13] Expressing voltage stability margin due to load apparent power as ( S VSM ), we have:Critical Load Critical S SS S VSM -= [14] Note that both Z VSM and S VSM are normalized quantities and their values decrease as the load increases.At the voltage collapse point, both the margins reduce to zero and the corresponding load is considered as the maximum permissible loading.Fig. 5. VIP algorithm2.2. Voltage Stability Margins and the Maximum Permissible LoadingSystem reaches the maximum load point when the condition: thev load Z Z =is satisfied (Figure5).Therefore the voltage stability boundary can be defined by a circlewith a radius of the Thévenin’s impedance. For normal operation the thev Z is smaller than load Z (i.e. it is outside the circle) and the system operates on the upper part (or the stable region) of a conventional P-V curve [2].However, when thev Z exceeds load Z the system operates on the lower part (or unstable region) of the P-V curve, indicating that voltage collapse has already occurred. At the maximum power point, the load impedance becomes same as the Thévenin’s (thev L Z Z ). Therefore, for a given load impedance (load Z ), the difference between thev Z and load Z can be considered as a safety margin. Hence the voltage as given in an IEEE survey, which described (111) schemes from (17) different countries [8].Fig. 6. Load actions to prevent from voltage instability2.3. Advantages of the proposed VIP algorithmBy incorporating the measurements from other load buses (Figure 3), the proposed VIP algorithm achieves a more accurate value of load Z . The on-line tracking of thev Z is used to track system changes.The proposed improvements in the VIP algorithm will result in better control action for power system voltage stability enhancement. The control measures are normally shunt reactor disconnection, shunt capacitor connection, shunt V ARcompensation by means of SVC’s and synchrouns condensers, starting of gas turbines, low priority load disconnection, and shedding of low-priority load [8]. Figure 6 shows the most commonly used remedial actions .3. ConclusionsAn improved V oltage Instability Predictor (VIP) algorithm for improving the voltage stability is proposed in this paper. The previous VIP method [7] used measurements only from the bus where the relay is connected. The new method uses measurements from other load buses as well. The voltage instability margin not only depends on the present state of the system but also on future changes.Therefore, the proposed algorithm uses an on-line tracking Thévenin’s equivalent for tracking the system trajectory. The algorithm is simple and easy to implement in a numerical relay. The information obtained by the relay can be used for load shedding activation at the bus or V AR compensation. In addition, the signal may be transmitted to the control centre,where coordinated system-wide control action can be undertaken. The algorithm is currently being investigated on an IEEE 30 bus system and results using the improved VIP algorithm will be reported in a future publication. References[1] M.H.Haque, “On line monitoring of maximum permissible loading of a power system within voltage stability limits”, IEE proc. Gener. Transms. Distrib.,V ol. 150, No. 1, PP. 107-112, January, 2003[2] V. Balamourougan, T.S. Sidhu and M.S. Sachdev, “Technique for online prediction of voltage collapse”, IEE Proc.Gener.Transm. Distrib., V ol.151, No. 4, PP. 453-460, July, 2004[3] C.A. Anizares, “On bifurcations voltage collapse and load modeling “IEEE Trans. Power System, V ol. 10, No. 1, PP. 512-522, February, 1995[4] T.J Overbye and S.J Demarco, “Improved Technique for Power System voltage stability assessment using energy methods“, IEEE Trans. Power Syst., Vol. 6, No. 4, PP. 1446-1452, November, 1991[5] P.A Smed Loof. T. Andersson, G. Hill and D.J,”Fast calculation of voltage stability index”, IEEE Trans. Power Syst. V ol. 7, No. 1, PP. 54-64, February, 1992[6] K. Ohtsuka ,” An equivalent of multi- machine power system and its identification for on-line application to decentralized stabilizers”, IEEE Trans. Power Syst., V ol. 4 No. 2, PP. 687-693, May, 1989[7] Khoi Vu, Miroslav M Begovic, Damir Novosel, Murari Mohan Saha, “ Use of local Measurements to estimate voltage –stability margin “ IEEE Trans. Power syst. Vol. 14, No. 3, PP. 1029-1035, August, 1999[8] G.V erbic and F. Gubina “Fast voltage-collapse line protection algorithm based on local phasors”, IEE Proc.Gener.Transm. Distrib., V ol. 150, No. 4, PP. 482-486, July, 2003译文:一种特殊的预防电压波动的保护方案摘要电压的波动与输电线路的最大负载能力密切相关。
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Brief Introduction to The Electric Power SystemPart 1 Minimum electric power systemA minimum electric power system is shown in Fig.1-1, the system consists of an energy source, a prime mover, a generator, and a load.The energy source may be coal, gas, or oil burned in a furnace to heat water and generate steam in a boiler; it may be fissionable material which, in a nuclear reactor, will heat water to produce steam; it may be water in a pond at an elevation above the generating station; or it may be oil or gas burned in an internal combustion engine.The prime mover may be a steam-driven turbine, a hydraulic turbine or water wheel, or an internal combustion engine. Each one of these prime movers has the ability to convert energy in the form of heat, falling water, or fuel into rotation of a shaft, which in turn will drive the generator.The electrical load on the generator may be lights, motors, heaters, or other devices, alone or in combination. Probably the load will vary from minute to minute as different demands occur.The control system functions (are)to keep the speed of the machines substantially constant and the voltage within prescribed limits, even though the load may change. To meet these load conditions, it is necessary for fuel input to change, for the prime mover input to vary, and for torque on the shaft from the prime mover to change in order that the generator may be kept at constant speed. In addition, the field current to the generator must be adjusted to maintain constant output voltage. Thecontrol system may include a man stationed in the power plant who watches a set of meters on the generator output terminals and makes the necessary adjustments manually. In a modern station, the control system is a servomechanism that senses generator-output conditions and automatically makes the necessary changes in energy input and field current to hold the electrical output within certain specifications..Part 2 More Complicated SystemsIn most situations the load is not directly connected to the generator terminals. More commonly the load is some distance from the generator, requiring a power line connecting them. It is desirable to keep the electric power supply at the load within specifications. However, the controls are near the generator, which may be in another building, perhaps several miles away.If the distance from the generator to the load is considerable, it may be desirable to install transformers at the generator and at the load end, and to transmit the power over a high-voltage line (Fig.1-2). For the same power, the higher-voltage line carries less current, has lower losses for the same wire size, and provides more stable voltage.In some cases an overhead line may be unacceptable. Instead it may be advantageous to use an underground cable. With the power systems talked above, the power supply to the load must be interrupted if, for any reason, any component of the system must be moved from service for maintenance or repair. Additional system load may require more power than the generator can supply. Another generator with its associated transformers and high-voltage line might be added.It can be shown that there are some advantages in making ties between the generators (1) and at the end of the high-voltage lines (2 and 3), as shown in Fig.1-3. This system will operate satisfactorily as long as no trouble develops or no equipmentneeds to be taken out of service.The above system may be vastly improved by the introduction of circuit breakers, which may be opened and closed as needed. Circuit breakers added to the system, Fig.1-4, permit selected piece of equipment to switch out of service without disturbing the remainder of system. With this arrangement any element of the system may be deenergized for maintenance or repair by operation of circuit breakers.Of course, if any piece of equipment is taken out of service, then the total load must be carried by the remaining equipment. Attention must be given to avoid overloads during such circumstances. If possible, outages of equipment are scheduled at times when load requirements are below normal.Fig.1-5 shows a system in which three generators and three loads are tied together by three transmission lines. No circuit breakers are shown in this diagram, although many would be required in such a system.Part 3 Typical System LayoutThe generators, lines, and other equipment which form an electric system are arranged depending on the manner in which load grows in the area and may be rearranged from time to time.However, there are certain plans into which a particular system design may be classified. Three types are illustrated: the radial system, the loop system, and the network system. All of these are shown without the necessary circuit breakers. In each of these systems, a single generator serves four loads.The radial system is shown in Fig.1-6. Here the lines form a “tree” spreading out from the generator. Opening any line results in interruption of power to one or more of the loads.The loop system is illustrated in Fig.1-7. With this arrangement all loads may be served even though one line section is removed from service. In some instances during normal operation, the loop may be open at some point, such as A. In case a line section is to be taken out, the loop is first closed at A and then the line section removed. In this manner no service interruptions occur.Fig.1-8 shows the same loads being served by a network. With this arrangement each load has two or more circuits over which it is fed.Distribution circuits are commonly designed so that they may be classified as radial or loop circuits. The high-voltage transmission lines of most power systems are arranged as network. The interconnection of major power system results in networks made up by many line sections.Part 4 Auxiliary EquipmentCircuit breakers are necessary to deenergize equipment either for normal operation or on the occurrence of short circuits. Circuit breakers must be designed to carry normal-load currents continuously, to withstand the extremely high currents that occur during faults, and to separate contacts and clear a circuit in the presence of fault. Circuit breakers are rated in terms of these duties.When a circuit breaker opens to deenergize a piece of equipment, one side of the circuit breaker usually remains energized, as it is connected to operating equipment. Since it is sometimes necessary to work on the circuit breaker itself, it is also necessary to have means by which the circuit breaker may be completely disconnected from other energized equipment. For this purpose disconnect switches are placed in series with the circuit breakers. By opening these disconnectors, thecircuit breaker may be completely deenergized, permitting work to be carried on in safety.Various instruments are necessary to monitor the operation of the electric power system. Usually each generator, each transformer bank, and each line has its own set of instruments, frequently consisting of voltmeters, ammeters, wattmeters, and varmeters.When a fault occurs on a system, conditions on the system undergo a sudden change. V oltages usually drop and currents increase. These changes are most noticeable in the immediate vicinity of fault. On-line analog computers, commonly called relays, monitor these changes of conditions, make a determination of which breaker should be opened to clear the fault, and energize the trip circuits of those appropriate breakers. With modern equipment, the relay action and breaker opening causes removal of fault within three or four cycles after its initiation.The instruments that show circuit conditions and the relays that protect the circuits are not mounted directly on the power lines but are placed on switchboards in a control house. Instrument transformers are installed on the high-voltage equipment, by means of which it is possible to pass on to the meters and relays representative samples of the conditions on the operating equipment. The primary of a potential transformer is connected directly to the high-voltage equipment. The secondary provides for the instruments and relays a voltage which is a constant fraction of voltage on the operating equipment and is in phase with it;similarly, a current transformer is connected with its primary in the high-current circuit. The secondary winding provides a current that is a known fraction of the power-equipment current and is in phase with it.Bushing potential devices and capacitor potential devices serve the same purpose as potential transformers but usually with less accuracy in regard to ratio and phase angle.中文翻译:电力系统的简介第一部分:最小电力系统一个最小电力系统如图1-1所示,系统包含动力源,原动机,发电机和负载。