输电英文

An Investigation into Extreme-Weather-Caused Transmission Line UnavailabilityD. O. Koval, Fellow, IEEE, and A. A. Chowdhury, Senior Member, IEEEAbstract-- One of the primary causes of major transmission line outages is extreme weather conditions particularly lightning, wind and conductor icing (e.g., Quebec, U.S. ice storms of 1998). The statistical results of a detailed analysis of an Alberta provincial utility‘s transmission line outage data base andAlberta Environmental Service weather data bases over a 20 yearperiod are investigated in this paper. The analysis will reveal thesignificance of the geographical location of the transmission lines and their frequency of outages. The paper will also reveal that the number of transmission line outages is not necessarily proportional to the physical length of the line for many transmission lines which contradict may publish methodologies. The paper provides the basic framework for constructing advanced probabilistic reliability models of transmission line networks (e.g., Markov models and Monte Carlo simulation models) based on the historical Canadian ElectricityAssociation‘s utility equipment reliability data base [1] and theEnvironmental Service weather data bases.Index Terms—Extreme weather, transmission line, availability, frequency of outages, Markov models I. INTRODUCTIONN today‘s deregulated power industry, the energy sources to supply a given geographical load can originate anywhere in North America as today‘s utilities are purcha sing economical energy from various geographical energy sources (e.g., out of province and out of country) and transporting the energy over various transmission line networks to load centers. New legislation throughout the world is presently focusing on the reliability of transmission lines during adverse weather conditions. The basic objective of transmission system adequacy assessment is to evaluate the ability of transmission system to transfer energy reliably between sources of generation and distribution load points. Any single or multiple transmission line outages can significantly alter the transmission system operating configuration such that continuity between energy delivery sources to system load points is interrupted [2]-[4]. One of the primary causes of major transmission line outages is extreme weather conditions particularly lightning, wind and icing [5]-[7]. These weather events are dependent upon the geographical location of theD. O. Koval is with Electrical Engineering Department, University of Alberta, Edmonton, Canada (e-mail: donkoval@shaw.ca) A. A. Chowdhury is with Electric System Planning, MidAmerican Energy Company, Davenport, IA, USA (e-mail: aachowdhury@) transmission line. This paper will focus on analyzing the extreme-weather caused an Alberta utility‘s transmission line outages in the Province of Alberta. The transmission line outage data base covers the entire area of the province and defines the primarycauses of transmission line outages, e.g., adverse weather, defective equipment, foreign interference, adverse environment, human element and systems conditions. The Alberta Provincial weather data base contains some of the following parameters: daily extreme temperature, daily extreme relative humidity, daily highest wind speed, monthly lightning records, monthly precipitation records, etc.,II. ADVERSE WEATHER STA TISTICS The weather elements that are considered to be adverseweather conditions are lightning, wind and precipitation. Amajor concern for utilities is the answer to the question: ―areadverse weather conditions a significant cause of transmission lines outages in my electric delivery system‖? The answer tothis question is clearly shown in Figures 1 and 2 where thefrequency of line-related outages is shown for all the utilitytransmission lines.Fig. 1. Primary causes of transmission line outagesThe frequency of each type of adverse weather event affecting each transmission line is shown in Figure 3 which reveals the variation in the impact of these elements on individual transmission lines. In comparing the primary causes of outages, adverse weather outages are significant accounting for approximately 33% of all outages as shown in Figure 2.Fig. 2. Frequency of adverse weather outages versus total number of outagesFig. 3. Frequency of lightning, wind and precipitation outages for each line outage.The impact of lightning wind and precipitation varies significantly between each transmission line as shown in Figure 3. A correlation analysis of the transmission line outage data revealed that wind and precipitation outages were not proportional to the physical length of transmission line. However, lightning outages were strongly correlated with the physical length of the transmission line. A summary of transmission line-related sustained forced outage statistics is shown in Table I.TABLE ITRANSMISSION LINE ―LINE-RELATED‖ OVERALLFORCED OUTAGE STATISTICSStatistic 72 kV 144 kV 240 kVFrequency per 100 km.a 1.521699 0.830133 0.882908 Mean duration (hours) 5.03 6.15 10.40 Median duration(hours)2.35 1.93 2.36Fig. 4. Percentage of transmission line outages by geographical region for agiven primary causeThe province of Alberta was divided into four distinctive geographical regions. It is clear from Figure 4 that the majority of transmission line outages occurred in the SE Region of the province (i.e., 56.2%), while the NW Region accounted for 36.9% of the transmission line outages and the NE Region only 6.9%. The SW Region of the province has very few major transmission lines in its territory and was not considered in this paper.The duration of transmission line outage statistics are shown in Tables II, III, IV and V for the various adverse weather primary causes.3TABLE IIDURATION OF TRANSM ISSION LINE ―LINE-RELATED‖ FORCED OUTAGESTA TISTICS (PRIMARY CAUSE – LIGHTNING)Statistic 72 kV 144 kV 240 kV Mean duration (hours) 7.12 104.21 1.45 Median duration (hours) 1.83 1.26 0.39 TABLE IIIDURATION OF TRANSMISSION ―LINE-RELATED‖ FORCED OUTAGESTA TISTICS (PRIMARY CAUSE – PRECIPITA TION)Statistic 72 kV 144 kV 240 kVMean duration (hours) 10.54 8.29 40.91 Median duration (hours) 2.64 1.62 6.77 TABLE IV DURATION OF TRANSMISSION ―LINE-RELATED‖FORCED OUTAGE STATISTICS (PRIMARY CAUSE – WIND)Statistic 72 kV 144 kV 240 kVMean duration (hours)5.79 7.03 23.04Median duration (hours) 4.42 2.19 1.29 TABLE VDURATION OF TRANSMISSION LINE ―LINE-RELATED‖FORCED OUTAGE STATISTICS(PRIMARY CAUSE – DEFECTIVE EQUIPMENT)Statistic 72 kV 144 kV 240 kV Mean duration (hours)5.42 40.20 11.16Median duration (hours)2.57 6.28 5.11It is important to note that for all the primary causes ofadverse weather, the duration of transmission line outage statistics varied significantly. The mean value and the medianvalue were significantly different implying the underlying statistical distributions for the duration of outages are not symmetrical and are skewed significantly. This skewness significantly impacts the mean value which is often used inreliability modeling of transmission lines. It is also important to note that the duration of outages for the various primary causes associated with adverse weathervaried significantly with the operating voltage level of the transmission line emphasizing the need to categorize transmission lines by voltage levels instead of grouping them into a single category. III. CONCLUSIONSThis paper has attempted to present the extreme (i.e., adverse) – weather caused transmission line outage statistics for a 20 year data bases of an Alberta provincial utility andEnvironment Services. The objective of the paper was to reveal the unique failure pattern and characteristics of transmission lines in the Province of Alberta. These statistics and the patterns of failure provide the framework forconstructing probabilistic reliability models of transmission lines operating in complex network configurations. The basic stratification of transmission line outage and weather data bases can be applied to any geographical area and any utilityin Canada.There is often the belief that extreme or adverse weather-related transmission line outages are an infrequent occurring event. This paper has clearly shown that adverse weather transmission line outages account for approximately one third of all transmission line outages in the Province of Alberta [6]. When adverse weather patterns affect a large geographical area and/or a concentrated number of transmission lines (e.g.,1998 Quebec Ice Storm), then part of or all of the transmission line network can be interrupted. In other cases,similar weather patterns may only interrupt a portion of the network but due to redundancy the transmission line network continuity of service to it load points can be maintained. This paper clearly revealed that the major cause of outages for some transmission lines was wind and precipitation (i.e.,freezing rain, snow, etc.) particularly in the south easternregion of the province. Also for all primary causes ofoutages, the south eastern region accounted for 56.2% of all transmission line outages. The application of overall provincial average transmission line outage statistics to aparticular transmission system configuration can lead toincorrect predictive reliability performance indices computed using the established system reliability assessmentmethodologies. IV. REFERENCES [1] Canadian Electricity Association, "Forced outage performance oftransmission equipment for the period Jan. 1, 1991 to Dec. 31, 1995‖, Montreal, Quebec, May 1996.[2] Electric Power Research Institute, "Predicting transmission outages for system reliability evaluations," EPRI-3880, Project 1468-2, May 1985. [3] D. O. Koval, ―Transmission equipment reliability data from CanadianElectrical Association‖, IEEE Transactions on Industry Applications, V ol. 32, No. 6, November/December 1996, pp. 1431-1439.[4] Recommended practice for the design of reliable industrial and commercial power systems, IEEE Std. 493-1998, (IEEE Gold Book).[5] D. O. Koval, ―Power system disturbance patterns‖, IEEE Transactions onIndustry Applications, V ol. 26, No. 3, May June, 1990, pp. 556-562. [6] A. A. Chowdhury, J. Voss, K. Berg, D. Frehlich, ―Development ofConsistent Transmission Outage Data Reporting and Analysis Procedures by Alberta Utilities‖, Canadian Electricity Association (CEA) Transactions, V olume 33, 1994.[7] A. A. Chowdhury, B. P. Glover, S. Herbert, A. Jensen, K. Stradley, and H. Turanli, ― Bulk Transmission Equipment Outage Performance Reporting atMid-Continent Area Power Pool‖, in Proceedings of ProbabilisticMethods Applied to Power Systems (PMAPS-2004) Conference (CD-ROM), Ames, Iowa, September 13-16, 2004.V. BIOGRAPHIESAli A. Chowdhury (A‘83—S‘86—M‘88—SM‘94) rec eived his M. Sc. Degree with Honors in electrical engineering from the Belarus Polytechnic Institute, Minsk, Belarus, the M. Sc. and Ph. D. degrees in electrical engineering with specialization in power systems reliability and security from the University of Saskatchewan, Saskatoon, Canada, and an MBA degree from the St. Ambrose University, Davenport, IA, USA. He has over 25 years of electric utility, electricequipment manufacturing industry, consulting, teaching, and R&D experience in power system reliability and security assessments, planning, and analysis. He is actively involved in the development of probabilistic models, criteria and software for use in power system planning, operating and maintenance. He has given invited lectures on power system reliability and security nationally and internationally. He has published about 90 peer reviewed technical papers including four ‗Best Prize Paper Awards‘ on the power system reliability and value-based utility system planning and design topics. He is currently with MidAmerican Energy Company, Davenport, Iowa.Dr. Chowdhury is a recipient of numerous national and international talent scheme scholarships covering his entire academic career. He received the IEEE Region 4 ‗2003 Outstanding Engineer of the Year A ward‘ for contributions to power system reliability and value-based system facilityplanning. He has been listed in International Biographical Center‘s ‗2004 Living Legends‘, Marquis‘s Who‘s Who in America, Who‘s Who in the World, and Who‘s who in Science and Engineering. Dr. Chowdhury is a Fellow of the British Institution of Electrical Engineers (IEE), a Chartered Engineer in the United Kingdom, a Registered Professional Engineer in the State of Texas, and in the Province of Alberta, Canada.D. O. Koval (S‘64-M‘65-SM‘78-F‘90) is a professor in the Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada. He teaches classes in Reliability Engineering, Power Quality, Power System Analysis, and ―IEEE Gold Book.‖ For 12 years, he was a Distribution Special Studies Engineer with B. C. Hydro and Power Authority, Vancouver, B. C., Canada, and for two years, he was a Sub-transmission Design Engineer with Saskatchewan Power, Regina, SK, Canada. He serves on the Board of Directors of several international societies, including the International Association of Science and Technology for Development (IASTED) and the International Institute for Advanced Studies in System Research and Cybernetics (ICSRIC). He has authored or coauthored more than 250 technical publications in the fields of emergency and standby power systems, power system reliability, human reliability, power system disturbances and outages, power quality, and computer system performance. He was the Editor of the IASTED International Proceedings on High Technology in the Power Industry, 1996.Dr. Koval is a Registered Professional Engineer in the Provinces of Alberta and British Columbia, Canada, a Fellow of the American Biographical Institute, and a Life Fellow of the International Biographical Center, Cambridge, U. K. He is listed in Marquis‘s Who‘s Who in the West, Who‘s Who in America, Who‘s Who in the World, Personalities of the Americans, Who‘s Who in Science and Engineering, 5000 Personalities of the Word, and i n the International Biographical Center‘s International Leaders of Achievement, International Who‘s Who of Intellectuals, and Men of Achievements. He was CO-Chairman of the 1998 IEEE/IAS Industrial and Commercial Power Systems Technical Conference held in Edmonton, AB, Canada. He is Chairman of IEEE Std. 493 (IEEE Gold Book). He was elected as one of the six Distinguished Lecturers of the IEEE industry Application Society (IAS) for the period 2000-2001. He was also recently appointed to the rank of Distinguished Visiting Professor and elected Fellow by the International Institute for Advanced Studies in System Research and cybernetics in Germany.。