Automated Distribution System Planning

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  • 12. THE USE OF SIMULATED RESERVE MARGINS TO DETERMINE SERVES, E. L. Arnoff, J. C. Chambers. Ibid., vol. 76, June 1957, pp.GENERATOR INSTALLATION DATES, C. J. Baldwin, D. P. Gaver, C. H. 316-28.Hoffman, J. A. Rose. Ibid., vol. 79, Aug. 1960, pp. 365-69.

    20. EVALUATION OF UNIT CAPACITY ADDITIONS, V. M. Cook, M. J.13. AN APPROACH TO PEAK LOAD ECONOMICS, C. D. Galloway, L. Kr. Steinberg. Ibid., VOl. 75, Apr. 1956, PP. 169-79.Kirchmayer, W. D. Marsh, A. G. Mellor. Ibid., pp. 527-35.14. NEW ANALYTICAL TOOLS PERMIT INTEGRATED SYSTEM PLAN- 21. AN INVESTIGATION OF ECONOMIC SIZE OF STEAM-ELECTRICNING, L. K. Kirchmayer, A. G. Mellor. Electrikal World, New York, GENERATING UNITS, L. K. Eirhmayer, A. G. Mellor, 3. F. O'Mara,N. Y., vol. 151, June 1, 1959, p. 52. J. R. Stevenson. Ibid., vol. 74, Aug. 1955, pp. 60009.15. ECONOMIC CHOICE OF GENERATOR UNIT SIZE, L. K. Kirchmayer, 22. APPLICATION OF PROBABILITY METHODS TO GENERATINGA. G. Mellor. Transactions, American Society of Mechanical En- CAPACITY PROBLEMS, AIEE Working Group on Applications ofgineers, New York, N. Y., vol. 80, July 1958, pp. 1015-26. Probability Methods. Ibid., vol. 79, 1960 (Feb. 1961 section), pp.

    1165-82.16. THE EFFECT OF INTERCONNECTIONS ON ECONOMIC GENERATIONEXPANSION PATTERNS, L. K. Kirchmayer, A. G. Mellor, H. 0. 23. DIGITAL COMPUTER AIDS ECONOMIC-PROBABILISTIC STUDY OFSimmons, Jr. AIEE Transactions, pt. III (Power Apparatus and GENERATION SYSTEMS-I, C. D. Galloway, L. K. Kirchmayer. Ibid.,Systems), vol. 76, June 1957, pp. 203-14. vol. 77, Aug. 1958, pp. 564-71.17. ECONOMIC SELECTION OF GENERATING CAPACITY ADDITIONS, 24. GENERATION PLANNING PROGRAM FOR INTERCONNECTEDT. W. Schroeder, G. P. Wilson. Ibid., vol. 77, Dec. 1958, pp. 1133- SYSTEMS. PART II-PRODUCTION COSTS, E. S. Bailey, Jr., C. D.45. Galloway, E. S. Hawkins, A. J. Wood. IEEE Transactions on Power18. DIGITAL PROGRAM FOR THE ECONOMIC SELECTION OF GENER- Apparatus and Systems, vol. 83, 1964.ATING CAPACITY ADDITIONS, A. Cohen, L. E. Jensen. Ibid., pp. 1628- 25. GENERATION PLANNING PROGRAM FOR INTERCONNECTED33. SYSTEMS. PART I-PROBABILITY PROGRAMS, E. S. Bailey, Jr., C. D.19. OPERATIONS RESEARCH DETERMINATION OF GENERATOR RE- Galloway, E. S. Hawkins, A. 3. Wood. Ibid.

    Automated Distribution System PlanningR. F. Lawrence, Senior Member IEEE F. E. Montmeat, Senior Member IEEEA. D. Patton, Member IEEE D. Wappler, Senior Member IEEE

    Improved methods of planning electric utility distribution Objectivessystems are necessary because the interrelationships among the One objective of this project is to provide the industrysystem variables are so complex that adequate analysis by with a tool which can promote agreement on standardizationexisting methods is not feasible. Selection of the most eco- of electric distribution equipment. Both manufacturers andnomical combination of subtransmission and distribution users have long recognized the advantages of standardizationvoltage levels, determination of economical substation sizes, of equipment and the consequent economies. Unfortunately,and comparison of different methods of regulating voltage are the analysis of distribution systems is so complex that eachproblems that must be studied in total system environment. utility must base its conclusions on piecemeal studies which

    Analyses and programs, previously reported, have con- yield different results in various systems. The most obvioustributed much to distribution system planning, but do not example is the multiplicity of primary distribution voltageadequately recognize some of the important factors such as levels that are being adopted or considered, ranging from 12.47actual geographical distribution of loads, configuration of the kv to 46 kv. If a consistent method of analysis, whichexisting system, step-by-step expansion of this system with considers all the factors involved, is utilized by a number oftime and load growth, or comparative reliability of various utilities, presumably the results of individual studies would bearrangements. -3 most helpful in defining the types and ratings of equipment

    Westinghouse Electric Corporation and Public Service Elec- required in the future.tric and Gas Company have co-operated to develop specifica- From the viewpoint of an individual utility system, the moretions for a realistic mathematical model of an electric utility complete examination of the entire system over a period ofsystem which permits quantitative evaluation and com- years permitted by this model will produce more accurateparison of alternative policies and plans for distribution sys- evaluations than the piecemeal studies of portions of the sys-tem expansion. This model consists of a number of sub- tem now used. Since system configurations, costs, and relia-models designed for solution on a large digital computer. bility criteria are developed on a consistent basis, they mayThe model has been developed for flexibility of interpretation logically be compared to help select the most desirable plan.and use so it may be adapted for analysis of various utility Use of this model to study various utility systems will help thesystems. This paper introduces the joint study and explains manufacturer meet the distribution apparatus requirementsthe specifications for these sub-models. Another paper de- of the utility industry.scribes in detail the design of the Reliability Sub-Model.4Paper 64-89, recommended by the IEEE Power System Engineering ScopeCommittee and approved by the IEEE Technical Operations Com- Apann rga o h eeainadbl-oemittee for presentation at the IEEE Winter Power Meeting, New A plnigpormfrtegeeainadbl-oeYork, N. Y., February 2-7, 1964. Manuscript submitted November transmission system has been described previously.5'64, 1963; made available for printing December 4, 1963. This study of the distribution system includes all facilitiesR. F. LAWRENCE and A. D. PATTON are with the Westinghouse Elec- from the bulk-power transmission lines to the customer'stric CDorporation, East Pittsburgh, Pa., and F. E. MONTMEAT and D. meter. This wide scope is necessary because the design of oneWAPPLER are with the Public Service Electric and Gas Company, oto fti ytmi lsl eae otedsgso h

    Newark, N. J.potooftisytmiclslreaetotedigsfthAPRIL 1964 Laworence, Montmeat, Patton, Wappler-Aultomated Distribultion System 311

  • other parts of the system. For example, if a change in the INPUTprimary distribution voltage level is being considered, the 2] PROPOSALS TO

    BE ANALYZEDstudy must include the effects of subtransmission voltage DESCRIPTION HISTORICAL 3 4levels, substation arrangements, capacities and locations, OF LAND USE AND TYPES DESISTEMshort-circuit duties, and reliability of the resulting system. DISTRIBUTION POPULATION OF NEW ANDIf various methods of regulating voltage are under investi- SYSTEM FORECASTS LOADS POLICIESgation, the factors studied must include the method of sup-plying reactive power, the effect of reactive power flow on LOAD FORECASTloads as well as voltage, the layout of primary distribution SUB-MODELfeeders, and the design of the distribution transformer-secondary combination.The present effort has been concentrated on the portion of SUB-MODEL

    the system from the transmission lines to the primary feeders. TA previously developed program has been modified to analyzethe distribution transformer-secondary combination.7 RELIABILITY


    Main Features BI OUTPUTAs illustrated in simplified form by the block diagram of a DESCRIPTION OF EXPANDED SYSTEM

    Fig. 1, some of the important features of the new model are as b. COST OF EXPANSIONlisted herewith.

    Fig. 1. Simplified block diagram, showing input, output, andINPUT DATA major sub-models of distribution planning modelBlock 1. Description of the existing distribution system in-cludes geographical arrangement of lines and substations aswell as electrical and thermal characteristics of these facili-ties. LOAD REPRESENTATIONBlock 2. Geographical distribution of existing loads is repre- Representation of geographical distribution and variablesented. Data on land use and population forecasts permit characteristics of new and existing load is more realistic thanforecasting loads on a geographical basis. the uniform distribution and characteristics usually assumed.Block 3. The effect of new types of loads which might be An undeveloped portion of the system which experiencesanticipated or promoted can be studied by inserting the rapid load growth often requires a different expansion planproper load characteristics and assumed distribution into the than a developed area which has a low growth rate. Econ-input data. omies often can be justified if the diversity of load cycleBlock 4. The planner can specify various voltage criteria, shapes between new and existing loads or between loads inplanning policies, or design characteristics which he wishes to adjacent areas can be recognized. These differences do notcompare. become apparent when uniform load distributions are as-

    SUB-MODELS sumed.Block 5. The Load Forecast Sub-Model produces forecasts of EXISTING SYSTEM REPRESENTATIONthe shape and magnitude of the load curve in each small sub- For existing substations and lines, the actual locations, de-division of the study area for each year to be studied. The signs, and limitations are used rather than idealized arrange-model combines the load curves for subdivisions to obtain the ments. In the more developed areas, the expansion patternsloads on lines, feeders, and substations. which fully utilize the existiing facilities usually prove to beBlock 6. The Distribution System Expansion Sub-Model the most economical. In less developed areas, the existingcompares loads and capacities of lines and stations; then system has less effect on the economics of future developments.makes a logical selection of plans to expand the system in A model which assumes idealized substation and feeder ar-accordance with proposed designs and policies specified by the rangements would not be able to distinguish between theseplanner. The investment costs and associated revenue re- situations. By its ability to represent the variety of arrange-quirements are calculated for the plans selected. ments of any actual system, this new model assures thatBlock 7. In the Reliability Sub-Model, six different factors the influence of the existing system is considered.are calculated to indicate the continuity of service that can be EXPANSION WITH TIMEexpected with each different system arrangement.

    A gradual step-by-step expansion plan for the system withOUTPUT time is developed rather than a series of static systems forBlock 8. The output includes: a description of the step-by- different load levels.step expansion plans; the investment costs and present worth A static model determines the total investment at selectedof all future revenue requirements associated with each plan; load levels but not the incremental investment each year.the reliability indexes. With these results, the various The timinlg of investmnents is frequently as important in makingpolicies and designs are compared and evaluated, the economic choice as the total investment. If Plan 1 requires

    a higher investment than Plan 2 at one load level and a lowerinvestment at another load level, only a present-worth analysis

    Improvements Over Previous Models of annual investments can determine the proper choice. IfThis model incorporates a number of improvements over different strategies result in the same ultimate system, the

    all distribution system models previously reported. choice is solely dependent on the investment schedule. In

    312 Lawrence, Montmeat, Patton, Wappler-Automated Distribution System APRIL 1964

  • this new model, the year-by-year investment schedule is establishes the boundaries of the basic load areas. In Fig.developed and then used to calculate the present worth of the 2(B), the total load in each basic load area is assumed to beassociated revenue requirements. located at the center of the area, and the dashed lines whichAnother problem associated with the use of a static model to conniect these centers indicate the approximate arrangement

    study a dynamic load area concerns the costs incurred in of loads on the mains. When load relief is required, thesemodifying a system at one load level to create a system ca- basic load areas are transferred to different feeders and substa-pable of providing service at a higher load level. The most tions as necessary.economic plan selected by a static program for one load levelcan be quite different from the most economic plan at a lower Load Sub-Modelload level. The cost of modifying the system from one design The function of the Load Sub-Model is to estimate the mag-to the other can offset all the apparent economies of the new nitude and shape of the load curves for real and reactivedesign. These extra costs cannot be adequately recognized power supplied to each basic load area on certain critical days,by the unrelated "snapshots" of the system through time de- such as a day of peak summer or peak winter load, for eachveloped by a static model. year to be studied. The use of load curves automatically

    introduces the proper diversity when combining and recom-RELIABILITY bining loads to obtain line and substation loads.New methods of calculating reliability indexes for the sys-

    tem have been developed so the quality of service offered by EXISTING LOADScompeting plans can be compared on a more rational basis Existing loads in each basic load area are determined bythan has been possible heretofore. alocating the measured load on each distribution feeder toGrid System one or more areas supplied by that feeder. An acceptable

    approximation of this allocation is obtained bv using theOne fundamental prerequisite for using this model is the following data:

    establishment of a grid system to permit systematic designa- . . . .c

    tion of the load and system component locations. Since d istributionT ransformersr c dithe be adsgeography is such a basic factor in distribution planning, a snumberofutilities have found grid co-ordinates useful fo can be allocated to the proper basic load areas in proportionnumbeof uilitishavfoun gri cooriate usfu for to measured or estimzated loads on the distribution trans-operating and planning distribution systems.89 Standard tormeasugrids such as latitude or longitude, or the 10,000-foot grids formers.shown on United States Geological Survey maps, are avail- Billing Data. Many utilities have added to each customer'sable, or special grids can be established. billing record an identification of the distribution transformerThe mnaps forming the base for all distribution system maps which supplies him, so that the customers can be assigned to

    by Public Service Electric and Gas Company include grid the proper basic load area through the grid co-ordinate of eachlines at each minute of latitude and longitude. The cost of transformer. If customers have not been so identified, appr...


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