电气专业毕业设计外文资料及中文翻译

外文资料：
Intellectual building electric protection and earth Summary : This text pass to several power supply earth systematic generalization introduction, is it suit as intellectual power supply earth system of building to screen, and has done comparatively exhaustive explanation and analysis to all kinds of earth measures should be takenned by it, electric protection that should adopt to the intellectual building and connecting the proper suggestion of local law proposition. Keyword:Load is balanced Electric potential form some earth , TN-S of datum point , defend static earth unify the earth body.
Support distribution in the design , earth is it occupy important status to design systematically in building, because it concerns the dependability of the electric power system , the security . No matter how many buildings, include earth design systematically always in supplying power design. And, different with requirements of the building, functions of all kinds of equipment are different, earth systems are corresponding and different too. Especially after entering the 1990s, a large number of intelligent appearance of building design and get a lot of new contents out of systematically earth. In daily several person who connects place, which kind be suit the intelligent building ? We might as well analyse several kinds of earth systems .
1.TN-C system
TN-C system call that into three-phase Line four system, systematic neutral line N this protect earth PE unite two into one, generally called PEN line. Although this kind of earth system is high in sensitivity to the earth trouble, circuit economy is simple, but it is only suitable for and used in three-phase load in the more balanced place . In the
intelligent building, single-phase load proportion relatively heavy, difficult to realize three-phase to be load balanced, disequilibrium electric current , PEN of line add because fluorescent lamp , brilliant floodgate person who in charge of high times of in harmony wave electric current that equipment cause that exist in the circuit, in it is not the trouble cases , will superpose at the N in neutral line , make the neutral line N voltage fluctuate, and electric current light and extremely unstable when being heavy, cause neutral some electric potential unstable to drift about earth. Not only will electrify equipment outer cover (connects with PEN line ) , cause the rights of the person unsafe, and unable to fetch to a suitable electric potential datum point, the accurate electronic equipment is unable to run accurately reliably. So TN-C earth system can't be regarded as the earth system of the intelligent building .
2.TN-C-S system
TN-C-S system is by two earth composition systematically, first part It is TN-C system, second part It is TN-S system, connect with PE line and click on N line the boundary. This system is generally used in the place attracted by regional switchyard of power supply of the building, enter family adopt TN-C system , enter households of place make repeated earth , enter after the family turning into TN-S system. Have already made analysis in front of TN-C system. The characteristic of TN-S system is: Neutral line N protect earth connection PE after grounding together while entering the family , can't have any electric connection. In this system, the neutral line N regular meeting protects the earth connection PE source without electricity with electricity. Equipment outer cover and metal component that PE line connects are in system normal running, will not be with electricity all the time. So TN-S earth system has obviously improved the securities of people and thing . At the same time so long as we adopt the earth lead wire, draw from earth body some each, choose correct earth resistance value
make electronic equipment obtain one electric potential datum point ,etc. measure together, then TN-C-S system can be regarded as a kind of earth system of the intelligent building.
3.TN-S system
TN-S is a earth system that three-phase Line four added PE line. Building usually is it enter line adopt this system when turning distribution into independently to have. The characteristic of TN-S system is, neutral line N and protecting earth connection PE except in the voltage transformer is grounded neutrally more together a bit, Line two no longer has electric connection of any. Neutral line N belong to electrification, but PE with electricity line. It's time to be grounded the system and totally possessed the safe and reliable basic electric potential. So long as like TN-C-S earth system, takes the same technological measure, TN-S system can be used as the earth system of the intellectual building. If such electronic equipment as the computer ,etc. generally adopt this kind of earth system without special requirement .
4.TT system
Usually call TT system the three-phase Line four earth system. This system supplies power to come from the place of the public electric wire netting dailily in the building. Characteristic, TT of system whether neutral line N protect earth connection PE have a bit electric to join, namely neutral some earth separate from that the line earth of PE is. When this system is in normal running, whether three-phase load is balanced, in case of neutral line N electrification, PE line will not be with electricity. Single-phase earth only at the trouble, protect earth to be low in sensitivity, the trouble can be cut off in time, the equipment outer cover is perhaps with electricity. TT system at the time of normal running is similar to TN-S system , can obtain the securities of people and thing and make the qualified basic earth electric potential too. With electric leakage appearance of
person who protect of large capacity, should systematic to can regard intelligent earth system of building as more and more too. According to present situation, because the power of the public electric wire netting is of low quality , difficult to meet the requirement for intelligent equipment, so TT system is seldom adopted by the intelligent building.
5.IT system
IT system three-phase the strategic hinterland of China earth system, system this voltage transformer neutral to ground or pass impedance earth a bit, have neutral line N , have only line voltage (380V), is it is it keep to press to have (220V), protect earth connection PE and is grounded independently each. System this advantage to when the earth , can make outer cover have larger trouble electric current as one phase, the system can run as usual . The shortcoming can not allot the neutral line N. So it is not suitable for the intelligent building with a large number of single-phase equipment .
In the intelligent building, demand to protect earth equipment very much, there is strong electric equipment , weak electric equipment, and the conductive equipment and component not with electricity, must adopt effective protection earth under some normal situations. If adopt TN-C system , use the N line in TN-C system as the earth connection at the same time ; Is it together , join N line and PE line really stiff to get on to connect among the system in TN-S; Set up electronic direct current earth lead wire of equipment and then , receive direct current earth on the PE line directly; Some clear-cut to is it answer together to mix N line , PE line , direct current earth connection. The above methods do not accord with earth requirement , and wrong. Have analysed , in the intelligent building, there is more single-phase power consuming equipment in in the front, single-phase load is relatively great in specific gravity, three-phase load is usually uneven, so there is random electric current in the neutral line N. In addition, because
adopt the fluorescent lamp to light in a large amount, the waves in harmony three times produced by it are superposed on the N line, have strengthened the electric current amount on the N line, if receive N line on the equipment outer cover , will cause shocking by electricity or fire accident ; If on connecting N line and PE line to receive the equipment outer cover in TN-S system, so dangerous and heavy, every receive equipment on the PE line, with electricity outer cover; Will expand the range which will shock by electricity the accident; Connect together except will take place above-mentioned dangers N line , PE line , direct current earth connection, the electronic equipment will be interfered being unable to work. So intelligent building should set up electronic direct current earth of equipment, exchanges earth, safe protection earth, and ordinary dyke thunder that building too should possess protect earth.
Now, we continue analysing various kinds of earth measures which should be taken in intelligent building .
1 .Whether defend thunder's earth: For is it channel earth into rapidly to flow thunder and lightning, taking preventing the thunder from hurting as purpose earth is it defend thunder's earth to call.
There are a large amount of electronic equipment and wiring system in the intelligent building, such as the communication automated system, the fire reports to the police and fire control link the control system , the automated system of the building , monitoring systems of security personnel, office automated system, the closed-circuit TV system,etc., and their corresponding wiring system. By the look of building built, the roof of every storey in the building, the baseplate, the side wall, hang and is nearly covered with by various kinds of wiring while carrying. These electronic equipment and wiring system generally belong to and able to bear the grade of pressing low , defend and interfere expecting much , is most afraid of the part struck by lightning. No matter
attack directly, bunch hit, is it can make electronic equipment the damage in various degree or interfere seriously to strike back. It designs to be must tight , reliable to intelligent dyke thunder earth of building. Intelligent all function earth of building, must in order to avoid thunder based on the system earth, set up tightly , intact dyke thunder structure.
The intelligent building is mostly first class load, should design according to the protective measure of first class Fang thunder building , connect person who flash adopt needle is it is it connect person who flash to make up to take , is it is it adopt 25* 4 (mm ) zinc-plated flat-rolled steel make up net of ≤ 10* 10 (m ) in roof to take to take shelter from the thunder, this net and metal component of the roofing are joined electrically, make and join with the building column cap reinforcing bar electrically, guide and roll off the production line and utilize the reinforcing bar in the column cap, enclose the reinforcing bar of roof beam , the floor reinforcing bar and defending the thunder system to join , other wall all metal component should with defend thunder system join , column cap reinforcing bar connect with earth body too, make up the shape of enveloping with multi-layer shielding and defend the thunder system. Can is it is it damage floor equipment to strike by lightning , but also still can prevent the outside electromagnetism from interfering to prevent effectively like this.
Earth resistance frequently of engineering of all kinds of dyke of thunder earth devices , should according to set thunder reaction terms at confirm generally. Defend if thunder device share one total earth at the network with job earth of electric equipment, earth resistance should accord with its minimum requirement .
2.The exchanges is grounded: Some any of power system, direct passing special equipment (such as impedance, resistance ,etc.), make metal join , call work earth with earth.
Job earth mean voltage transformer neutral a bit or neutral line (N line ) earth mainly. N line must spend copper core insulating line. There is wiring end son of the electric potential such as being auxiliary in the distribution , wait for the wiring end son of the electric potential generally in the case cupboard. Must notice , should wire the end son and can expose ; Can't with other earth system, such as direct current earth, shielding earth, defend static earth is it is it connect to mix to wait for; Can't connect with PE line either.
In high-pressure system , adopt neutral some person who connects place can make earth relay protection accurate movement and dispel single-phase electric arc earth overvoltage. Can prevent the skew of voltage of zero preface , keep the three-phase voltage in a basic balance in some neutral earth, this is very meaningful to low-voltage system, can be convenient to use the single-phase power.
3.Safe protection is grounded: Safe protection earth metal part and earth body with electricity make good metal join electric equipment. Namely power consuming equipment and some metal components near the equipment of building, join with PE thread, but forbid connecting PE line with N line.
In the intelligent building, require there is very much earth equipment of safe protection , there is strong electric equipment , weak electric equipment, and some conductive equipment and component with electricity, must take safe protection earth measure. When insulation not doing the earth electric equipment of safe protection is damaged , its outer cover is possible with electricity. If the outer cover that the human body touches this electric equipment may be wounded or caused the life danger by the electricity. Among neutral power system that ground directly a bit, earth short out electric current pass personal, the earth flows back to a bit more neutrally; In a bit more neutrally power system not grounded directly , the earth electric current flows into the
earth through the human body, and form thorough fare by electric capacity by circuit to ground, two situation these can lead to the fact the rights of the person get an electric shock.
If the insulation which is equipped with the electric equipment of the earth device is damaged while electrifying outer cover , short out in the electric current and flow through two thorough fares of earth body and human body at the same time in earth, I =IL + IP, we know: In a parallel circuit, the electric current value of passing each branch road is in inverse proportion to size of the resistance.
In the type: I - Electric current total value in the earth return circuit
IL - Electric current flowing through along the earth body
IP - Flow through electric current of the human body
Have type can find out earth resistance little , flow through to little electric current have human body, human resistance usually is it ground than earth resistance through electric current of human body electric current of body have several hundred less flowing through too to have several hundred heavier. When earth resistance is extremely small, the electric current that remakable body flows nearly equals zero. Namely I≈IL. In fact, because earth resistance very little, earth short out electric current flow out of date produce press and lower very lightly, so equipment outer cover voltage in earth high. People stand while going to touch the outer cover of the equipment on the earth, the voltage that the human body bears is very low, it can not be dangerous.
Is it protect earth device and reduce earth resistance of it to install additional , not only ensure the electric security of system of intelligent building, the effective measure operated effectively, it is not the essential means of equipment and personal security in the intelligent building that ensure too.
4.Direct current is grounded: In a block of intelligent building , include a large
number of computers , communication apparatus and automation equipment of building with computer. Importing to information in these electronic equipment, transmission information, change energy , amplify signal, logic movement, output information a series of course go on through little electric potential or little electric current fast, and will often carry on the work through the internet between the equipment. So in order to make its accuracy high, the stability is good, besides needing to have a steady power supply power, must also possess a steady basic electric potential . Can adopt bigger and sectionaller insulating copper core line as the lead wire , one end is connected with basic electric potential directly, another end support electronic equipment direct current earth. It is unsuitable to connect with PE line to deserve and go between , forbid connecting with N line.
5.Whether shielding earth defend static earth: In the intelligent building, it is very important to design electromagnetic and compatibly, in order to avoid the dysfunctions of the equipment used, equipment can appear evenned to prevent from damage, form equipment of wiring system should can prevent inside oneself conduct and extraneous interference from. Or because of the coupling phenomenon between the wire in these production that interfere, or because of the electric capacity effect or inductance effect. Main source its superelevation voltage, high-power pieces of radio magnetic field, strike by lightning naturally and static discharge. Phenomenon these will is it send or receive very high to transmit equipment of frequency produce heavy interference very to used for designing. Is it must take the protective measure to equipment the to connect up , avoid the interference from various kinds of respects. Shielding and correct earth to prevent electromagnetic best protection method that interfere. Can connect the equipment outer cover with PE line ; Require both ends of
shielding pipeline and PE line to join reliably in shielding earth of the wire; Indoor shielding should a lot of some is joined with PE thread reliably. It is very important too to defend static interference. In clean, dry room, walking , mobile device of people, is it can produce a large amount of static to grit each. For example 10-20% environmental walking of middleman can gather volt of static voltages , have good earth in relative humidity, will not merely produce the interference to the electronic equipment , even will break the equipment chip . Bring static object or may produce object (insulator ) of static through lead static body and earth form electric earth of return circuit is it defend static earth to call. Defend static earth require of clean quiet dry environment, all equipment outer cover and getting indoor facility must with line many to join reliably a bit PE have.
Earth device of intelligent building little and kind earth resistance have, independent dyke thunder prote ct earth resistance in conformity with ≤ 10Ω; Independent safe protection earth resistance is in conformity with ≤ 4Ω; Independent exchanges earth resistance is in conformity with ≤ 4Ω; The independent working earth resistance of direct current is in confo rmity with ≤ 4Ω; Defend static earth resistance demand ≤ 100Ω the same.
Intelligent power supply earth system of building should adopt TN-S system , should adopt according to norm one a total one common to ground the device , namely unify the earth body. It is a earth electric potential datum point to unify the earth body , therefore draw various kinds of function earth lead wire separately, the way of the electric potential of utilize electric potential such as being total and auxiliarying etc. makes up an intact unified earth system.Generally, unify earth system usable pile reinforcing bar of building, and zinc-plated flat-rolled steel link an organic whole it with 40* 4 (mm), as the natural earth body. According to norm, should systematic defending thunder earth
share systematically , in conformity with ≤ 1Ωearth resistance its. If can not reach the requirement , must increase artificial earth body or adopt chemistry lower law of hindering , make ≤ 1Ω of earth resistance . In turn into distribution is i t wait for electric potential copper arrange always to set up , copper this arrange one end through construct post or reinforcing bar of baseplate connect with unified earth body, another end join with exchanges neutral line , earth of system separately through different connection end son, with is it make safe protection earth every equipment join , with defend thunder's system join to need, join with the insulating copper core earth connection needing to make the earth electronic equipment of direct current. Among intellectual mansion, because system adopt computer is it manage or use computer as job tool to participate in, should adopt some earth not single of so earth of it system and should taking electric potential measure. Single some earth is it protect earth , job earth , direct current earth separate each other at the equipment to mean, it is systematic to become independence each. Can draw three insulating ground terminal each other from cabinet , and then guide to always waiting for the electric potential copper to arrange having and is grounded together from the lead wire. Is it is it together , is it wait for electric potential copper is it have to arrange always to receive three earth with lead wire and then to bind to allow. This to mix earth in fact, this kind connect law to be unsafe to can is it interfere to produce also, the present norm is not allowed .
中文翻译：
智能楼宇的电气保护与接地
摘要:本文通过对几种供电接地系统的概括介绍，筛选出适合作为智能楼宇的供电接地系统，并对其所应采取的各类接地措施作了较为详
尽的说明与分析，对智能楼宇应采取的电气保护与接地方法提出了适当的建议。

关键词: 负荷平衡电位基准点TN－S 单点接地防静电接地统一接地体
在建筑物供配电设计中，接地系统设计占有重要的地位，因为它关系到供电系统的可靠性，安全性。

不管哪类建筑物，在供电设计中总包含有接地系统设计。

而且，随着建筑物的要求不同，各类设备的功能不同，接地系统也相应不同。

尤其进入90年代后，大量的智能化楼宇的出现对接地系统设计提出了许多新的内容。

在常用的几种接地方式中，哪一种能够适合智能化楼宇呢？我们不妨分析一下下面几种接地系统。

1.TN－C系统
TN－C系统被称之为三相四线系统，该系统中性线N与保护接地PE 合二为一，通称PEN线。

这种接地系统虽对接地故障灵敏度高，线路经济简单，但它只适合用于三相负荷较平衡的场所。

智能化大楼内，单相负荷所占比重较大，难以实现三相负荷平衡，PEN线的不平衡电流加上线路中存在着的由于荧光灯、晶闸管（可控硅）等设备引起的高次谐波电流，在非故障情况下，会在中性线N上叠加，使中性线N电压波动，且电流时大时小极不稳定，造成中性点接地电位不稳定漂移。

不但会使设备外壳（与PEN线连接）带电，对人身造成不安全，而且也无法取到一个合适的电位基准点，精密电子设备无法准确可靠运行。

因此TN－C 接地系统不能作为智能化建筑的接地系统。

2.TN－C－S系统
TN－C－S系统由两个接地系统组成，第一部分是TN－C系统，第二部分是TN－S系统，分界面在N线与PE线的连接点。

该系统一般用在建
筑物的供电由区域变电所引来的场所，进户之前采用TN－C系统，进户处做重复接地，进户后变成TN－S系统。

TN－C系统前面已做分析。

TN －S系统的特点是：中性线N与保护接地线PE在进户时共同接地后，不能再有任何电气连接。

该系统中，中性线N常会带电，保护接地线PE没有电的来源。

PE线连接的设备外壳及金属构件在系统正常运行时,始终不会带电.因此TN－S接地系统明显提高了人及物的安全性.同时只要我们采取接地引线,各自都从接地体一点引出,及选择正确的接地电阻值使电子设备共同获得一个等电位基准点等措施,那么TN－C－S系统可以作为智能型建筑物的一种接地系统。

3.TN－S系统
TN－S是一个三相四线加PE线的接地系统。

通常建筑物内设有独立变配电所时进线采用该系统。

TN－S系统的特点是，中性线N与保护接地线PE除在变压器中性点共同接地外，两线不再有任何的电气连接。

中性线N是带电的，而PE线不带电。

该接地系统完全具备安全和可靠的基准电位。

只要象TN－C－S接地系统，采取同样的技术措施，TN－S系统可以用作智能建筑物的接地系统。

如果计算机等电子设备没有特殊的要求时，一般都采用这种接地系统。

4.TT系统
通常称TT系统为三相四线接地系统。

该系统常用于建筑物供电来自公共电网的地方。

TT系统的特点是中性线N与保护接地线PE无一点电气连接，即中性点接地与PE线接地是分开的。

该系统在正常运行时，不管三相负荷平衡不平衡，在中性线N带电情况下，PE线不会带电。

只有单相接地故障时，由于保护接地灵敏度低，故障不能及时切断，设备外壳才可能带电。

正常运行时的TT系统类似于TN－S系统，也能获得人与
物的安全性和取得合格的基准接地电位。

随着大容量的漏电保护器的出现，该系统也会越来越作为智能型建筑物的接地系统。

从目前的情况来看，由于公共电网的电源质量不高，难以满足智能化设备的要求，所以TT系统很少被智能化大楼采用。

5.IT系统
IT系统是三相三线式接地系统，该系统变压器中性点不接地或经阻抗接地，无中性线N，只有线电压（380V），无相压压（220V），保护接地线PE各自独立接地。

该系统的优点是当一相接地时，不会使外壳带有较大的故障电流，系统可以照常运行。

缺点是不能配出中性线N。

因此它是不适用于拥有大量单相设备的智能化大楼的。

在智能化楼宇内，要求保护接地的设备非常多，有强电设备，弱电设备，以及一些正常情况下不带电的导电设备与构件，均必须采用有效的保护接地。

如果采用TN－C系统，将TN－C系统中的N线同时用做接地线；或者在TN－S系统中将N线与PE线接在一起，再连接到底板上去；再或不设置电子设备的直流接地引线，而将直流接地直接接到PE线上；有的干脆把N线、PE线、直流接地线混接在一起。

以上这些做法都是不符合接地要求的，且是错误的。

前面已经分析过，在智能化大楼内，单相用电设备较多，单相负荷比重较大，三相负荷通常是不平衡的，因此在中性线N中带有随机电流。

另外，由于大量采用荧光灯照明，其所产生的三次谐波叠加在N线上，加大了N线上的电流量，如果将N线接到设备外壳上，会造成电击或火灾事故；如果在TN－S系统中将N线与PE 线连在一起再接到设备外壳上，那么危险更大，凡是接到PE线上的设备，外壳均带电；会扩大电击事故的范围；如果将N线、PE线、直流接地线均接在一起除会发生上述的危险外，电子设备将会受到干扰而无法工作。

因此智能建筑应设置电子设备的直流接地，交流工作接地，安全保护接
地，及普通建筑也应具备的防雷保护接地。

下面，我们接着分析一下智能化楼宇应采取的各种接地措施。

１.防雷接地：为把雷电流迅速导入大地，以防止雷害为目的的接地叫作防雷接地。

智能化楼宇内有大量的电子设备与布线系统，如通信自动化系统，火灾报警及消防联动控制系统，楼宇自动化系统，保安监控系统，办公自动化系统，闭路电视系统等，以及他们相应的布线系统。

从已建成的大楼看，大楼的各层顶板，底板，侧墙，吊顶内几乎被各种布线布满。

这些电子设备及布线系统一般均属于耐压等级低，防干扰要求高，最怕受到雷击的部分。

不管是直击，串击，反击都会使电子设备受到不同程度的损坏或严重干扰。

因此对智能化楼宇的防雷接地设计必须严密，可靠。

智能化楼宇的所有功能接地，必须以防雷接地系统为基础，并建立严密，完整的防雷结构。

智能建筑多属于一级负荷，应按一级防雷建筑物的保护措施设计，接闪器采用针带组合接闪器，避雷带采用25×4（mm）镀锌扁钢在屋顶组成≤10×10（m）的网格，该网格与屋面金属构件作电气连接，与大楼柱头钢筋作电气连接，引下线利用柱头中钢筋，圈梁钢筋，楼层钢筋与防雷系统连接，外墙面所有金属构件也应与防雷系统连接，柱头钢筋与接地体连接，组成具有多层屏蔽的笼形防雷体系。

这样不仅可以有效防止雷击损坏楼内设备，而且还能防止外来的电磁干扰。

各类防雷接地装置的工频接地电阻，一般应根据落雷时的反击条件来确定。

防雷装置如与电气设备的工作接地合用一个总的接地网时，接地电阻应符合其最小值要求。

2.交流工作接地：将电力系统中的某一点，直接或经特殊设备（如
阻抗，电阻等）与大地作金属连接，称为工作接地。

工作接地主要指的是变压器中性点或中性线（N线）接地。

N线必须用铜芯绝缘线。

在配电中存在辅助等电位接线端子，等电位接线端子一般均在箱柜内。

必须注意，该接线端子不能外露；不能与其它接地系统，如直流接地，屏蔽接地，防静电接地等混接；也不能与PE线连接。

在高压系统里，采用中性点接地方式可使接地继电保护准确动作并消除单相电弧接地过电压。

中性点接地可以防止零序电压偏移，保持三相电压基本平衡，这对于低压系统很有意义，可以方便使用单相电源。

3.安全保护接地：安全保护接地就是将电气设备不带电的金属部分与接地体之间作良好的金属连接。

即将大楼内的用电设备以及设备附近的一些金属构件，用PE线连接起来，但严禁将PE线与N线连接。

在智能化楼宇内，要求安全保护接地的设备非常多，有强电设备，弱电设备，以及一些非带电导电设备与构件，均必须采取安全保护接地措施。

当没有做安全保护接地的电气设备的绝缘损坏时，其外壳有可能带电。

如果人体触及此电气设备的外壳就可能被电击伤或造成生命危险。

在中性点直接接地的电力系统中，接地短路电流经人身，大地流回中性点；在中性点非直接接地的电力系统中，接地电流经人体流入大地，并经线路对地电容构成通路，这两种情况都能造成人身触电。

如果装有接地装置的电气设备的绝缘损坏使外壳带电时，接地短路电流将同时沿着接地体和人体两条通路流过，I=IL＋IP，我们知道：在一个并联电路中，通过每条支路的电流值与电阻的大小成反比。

式中：I—接地回路中的电流总值
IL—沿接地体流过的电流
IP—流经人体的电流
由上式可以看出，接地电阻越小，流经人体的电流越小，通常人体电
阻要比接地电阻大数百倍经过人体的电流也比流过接地体的电流小数百倍。

当接地电阻极小时，流过人体的电流几乎等于零。

即I≈I L。

实际上，由于接地电阻很小，接地短路电流流过时所产生的压降很小，所以设备外壳对大地的电压是不高的。

人站在大地上去碰触设备的外壳时，人体所承受的电压很低，不会有危险。

加装保护接地装置并且降低它的接地电阻，不仅是保障智能建筑电气系统安全，有效运行的有效措施，也是保障非智能建筑内设备及人身安全的必要手段。

4.直流接地：在一幢智能化楼宇内，包含有大量的计算机，通讯设备和带有电脑的大楼自动化设备。

在这些电子设备在进行输入信息，传输信息，转换能量，放大信号，逻辑动作，输出信息等一系列过程中都是通过微电位或微电流快速进行，且设备之间常要通过互联网络进行工作。

因此为了使其准确性高，稳定性好，除了需有一个稳定的供电电源外，还必须具备一个稳定的基准电位。

可采用较大截面的绝缘铜芯线作为引线，一端直接与基准电位连接，另一端供电子设备直流接地。

该引线不宜与PE线连接，严禁与N线连接。

5.屏蔽接地与防静电接地：在智能化楼宇内，电磁兼容设计是非常重要的，为了避免所用设备的机能障碍，避免甚至会出现的设备损坏，构成布线系统的设备应当能够防止内部自身传导和外来干扰。

这些干扰的产生或者是因为导线之间的耦合现象，或者是因为电容效应或电感效应。

其主要来源是超高电压，大功率幅射电磁场，自然雷击和静电放电。

这些现象会对设计用来发送或接收很高传输频率的设备产生很大的干扰。

因此对这些设备及其布线必须采取保护措施，免受来自各种方面的干扰。

屏蔽及其正确接地是防止电磁干扰的最佳保护方法。

可将设备外
壳与PE线连接；导线的屏蔽接地要求屏蔽管路两端与PE线可靠连接；室内屏蔽应多点与PE线可靠连接。

防静电干扰也很重要。

在洁净、干燥的房间内，人的走步、移动设备，各自磨擦均会产生大量静电。

例如在相对湿度10～20%的环境中人的走步可以积聚3.5万伏的静电电压、如果没有良好的接地，不仅仅会产生对电子设备的干扰，甚至会将设备芯片击坏。

将带静电物体或有可能产生静电的物体（非绝缘体）通过导静电体与大地构成电气回路的接地叫防静电接地。

防静电接地要求在洁静干燥环境中，所有设备外壳及室内（包括地坪）设施必须均与PE线多点可靠连接。

智能建筑的接地装置的接地电阻越小越好，独立的防雷保护接地电阻应≤10Ω；独立的安全保护接地电阻应≤4Ω；独立的交流工作接地电阻应≤4Ω；独立的直流工作接地电阻应≤4Ω；防静电接地电阻一般要求≤100Ω。

智能化楼宇的供电接地系统宜采用TN－S系统，按规范宜采用一个总的共同接地装置，即统一接地体。

统一接地体为接地电位基准点，由此分别引出各种功能接地引线，利用总等电位和辅助等电位的方式组成一个完整的统一接地系统。

通常情况下，统一接地系统可利用大楼的桩基钢筋，并用40×4（mm）镀锌扁钢将其连成一体，作为自然接地体。

根据规范，该系统与防雷接地系统共用，其接地电阻应≤1Ω。

若达不到要求，必须增加人工接地体或采用化学降阻法，使接地电阻≤1Ω。

在变配电所内设置总等电位铜排，该铜排一端通过构造柱或底板上的钢筋与统一接地体连接，另一端通过不同的连接端子分别与交流工作接地系统中的中性线连接，与需要做安全保护接地的各设备连接，与防雷系统连接，与需做直流接地的电子设备的绝缘铜芯接地线连接。

在智能大厦中，因为系统采用计算机参与管理或使用计算机作为工作工具，所以其接地系。