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

    SUB-MODEL.

    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, appro-adding any other grid to these maps could inot be justified, priate maps and directories can be used to make these assign-so the latitude and longitude grid is retained, despite some ments. At least one commercial source has compiled suchobvious disadvantages of such nonuniformitv. However, to data on magnetic tape for computer applications.avoid using degrees, minutes, and seconds, a special number- Billing data used for load allocation are: kilowatt-hour con-ing system based on minutes and decimal parts of minutes has sumption; dernands; rate and other classifications which in-been adopted. dicate the nature of the load.The area to be studied is divided into basic load areas, which Customer Load Curves. Manv utilities perform tests to deter-

    are bounded by grid lines and designated by grid co-ordinates. mine typical load curves and load factors for various rate andLoad densities determine the basic load area size. In the consumtption classes of customers, and some of the results arePublic Service territory, dimensions of 0.2 minute of longi- made available to the utility industry through the reports oftude by 0.2 minute of latitude, or about 1/25 of a square mile, the Association -of Edison Illuminating Companies Loadappear feasible in the areas with higher load densities. Research Committee. By combining-these data aiththe

    Fig. 2 illustrates how a primary distribution feeder and the billing data, appropriate load eurves for basic load areas canfeeder load area are represented by a group of connected basic be synthesized.load areas. Fig. 2(A) is a map of the mains of a typical feeder,with a superimposed 0.2-minute-by-0.2-minute grid, which Feeder and Substation Load Curves. The synthesized load

    curves for basic load areas are combined into feeder andsubstation load curves; then compared with measured curvesand adjusted accordingly.

    l \ >e\\ . . , , s ---. ~~Fig. 2. Illustration of how primary distribution! [ i /\C \t/ 0 . < ~~~feeder and feeder load area are represented by

    ,< < q > .+ t. ~~~~~~~~groupof connected basic load areas/ [ \1\ \ t + X ,----

    .f--ll$ A--Typical distribution feeder and mains with* i \ >) - \ ----1- -W superimposed grid

    I i

  • FORECAST LOADS range strategies for the expansion of distribution systems.The forecast of loads in basic load areas is based on: This procedure requires laborious data processing, interspersed. f o :with decision making. The planner bases these numerousExisting Customers. Normal increase in usage by existing hdecisons onhis own experience and judgment, plus many

    customers is estimated. The effect of promoting new types otherires oures. Sow rtrngepanningfrnals tonbof utilization equipment can be studied by adding typical load ocurves and projected saturations to the curves of existing constructed immediately requires him to consult all possibleloads. sources such as maps, equipment designs and costs, operatingrecords, and individuals inside and outside his own organiza-Land Use. Existing land uses -and uses projected by zoning tion. But fng-ranl in vehstiat oal niatordinances and planning boards will indicate future possi- ution. But for ong-range planndng, to mnuestigate alternativebilities for each area. Basic load areas in parks, cemeteries, order to look at the broad picture. The logic developed hereinand other restricted areas are designated as "No Load." Other indedto s lthe long-range studyvprocedurebuZ: iS intended to simulate the long-range study procedure butareas are designated for residential, commercial, or industrial not the short-range planning process.development. Planners may introduce into this model as much of their ownPopulation Forecasts. Some municipal and county planning experience and judgment as they desire. The general logicboards have prepared, or will co-operate in preparing, included in the program is used only after all suggestions of theestimates of future growth of residential, industrial, and planner have been considered. This is particularly useful incommercial areas. More recently, transportation committees the early years of the study when so many of the expansionformed in urban areas also make such projections. Public steps have been committed.Service Company has compiled and periodically up-dates apopulation forecast for each municipality, based on all avail- OUTLINE OF PROCEDUREable sources. By allocating the projected population increaseto the residential areas selected in the land-use survey, the Foloedci teaSytem Expansion S odl.growth in residential customers in each basic load area isestimated. 1. Projects which are committed and specified by the plan-

    ner are added to the existing system.Area and System Forecasts. The forecasts for basic load areasarecombined to obtain feeder, substation, area, and system 2. Forecast loads on all S-D, S(T)-D, and T-D substations areloar e ' ' t accumulated from the data supplied by the Load Sub-Model forload forecasts. If necessary, the basic load area forecasts are the year under study, plus the 3 following years. The loads for

    adjusted so the synthesized system load forecast matches the several years are required because selection of plans for relief ofsystem forecast prepared by present methods. overloaded stations is partly based on anticipated loads and

    capacities.3. The forecast loads are compared with the capacities of thesesubstations; then the method of relieving the overloads is deter-

    The function of the System Expansion Sub-Model is to mined, and loads and capacities are adjusted accordingly. Theprepare plans and costs for expanding the existing distribution logic used in this step is described in a subsequent section.system as necessary to provide capacitv for the loads fore- 4. The revised loads for S-D and S(T)-D substations, togethercast by the Load Sub -Model. with the loads supplied directly at subtransmission voltage, are

    combined to obtain the loads on the T-S substations. For inte-grated subtransmission networks supplied by more than one T-S

    DEFINITIONS substation, distribution factors must be obtained from previousThe following definitions of voltage levels are used in load-flow studies to permit approximate allocation of the network

    this sub-model: load to the proper T-S substation.5. Forecast loads are compared with capacities for the T-S sub-

    Distribu.tion voltage iS the voltage at which the load in a basic stations, then the method of relieving the overloads is deter-load area is supplied. mined. The major steps of relief for T-S substations are speci-Subtransmission voltage is used to supply substations which fied by the planner in the input data since these steps wouldtransform to distribution voltage and may also be used as a usually be important policy decisions which are to be examineddistribution voltage. by the model. The following types of relief are possible:

    a. Add capacitors up to a specified maximum power factor.Transmission voltage is used to supply substations which .TStransform to subtransmission voltage and may also be used as

    c. Transfer distribution load to a T-D substation.a subtransmission or distribution voltage.

    ..alttthe explanation of this sub-model, a few d. Transfer S-D substations to adjacent T-S substations whichTo faclitate have surplusocapacity.mdel afespecial abbreviations are used to indicate substation types: have surplus capacity.

    e. Reinforce the overloaded station or adjacent stations to ac-T-S substation transforms from transmission to subtransmis- commodate the load.sion voltage. f. Install a new T-S substation.T-D substation transforms from transmission to distribution After the method of relief is determined, loads and capacitiesvoltage. are adjusted accordingly.S-D substation transforms from subtransmission to distribu- 6. Using the revised substation loads and a simplified load-flowtion voltage. program, the subtransmission system is analyzed to determineS(T)-D substation initially transforms from subtransmission the need for additional facilities to relieve subtransmission line

    distribution ~votg*usdsge ob hne otas overloads and subnormal bus voltages. The general logic in-to~~~~~~~~~~~~~~~~~cludedin the model selects the method of relief from the following

    mission voltage supply when desired. priority list, but this list can be modified or supplemented byentries in the input data.

    BASIS FOR MODEL LOGIC a. Add capacitors up to a specified maximum power factor.A logical sequence of operations has been developed which h. Reinforce existing overloaded suhtransmission lines if pos-

    simulates the complicated procedure now used to study long- sible.

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

  • c. Transfer S(T)-D substations to transmission supply. vided by each plan developed by the System Expansion Sub-d. Install new subtransmission lines. Model. A cost comparison between these plans is meaning-e. Install additional voltage regulating equipment. less unless the reliability is also compared. Cheaper plans7. The particular basic load areas which must be transferred be- can always be devised if reliabilty can be sacrificed, but suchtween substations to provide the required relief are selected. sacrifice is rarely acceptable in this day of increasing de-8. The loadings and voltages on the distribution circuits are pendence on continuous electric supply.examined to determine the need for new distribution circuits and Since no single measure of reliability is completely satis-voltage regulating equipment. factory for this comparison, six different indexes have been9. The costs for the study year are accumulated; then time selected for this purpose. These indexes and the methodsadvances 1 year, and steps 1 through 8 are repeated for the next of calculating the probable values are described in anotheryear. paper. I

    The calculated indexes for each plan can be compared withDTheIfoluTwinSuBStATiOn RELIfprocedurefordeterminingt historical values for the existing system as well as with cal-The following outline of procedure for determining the culated values for other plans. Many companies have been

    method of relieving overloads on distribution substations compiling reliability statistics based on actual experience and,(Step 3 of the general procedure) illustrates the detailed logic in most cases, would expect that the over-all reliability ofwhich has been developed to implement the general procedure. the system would not be reduced below present levels. If theThe intent is to select the most economical relief measures calculated indexes for a particular plan are below desirable

    for the overloaded distribution substations. However, rvalues, the design standards in the input data must bethere are so many possible plans for relief which might be changed to improve the reliability. If one plan has bothconsidered that complete economic comparisons for each would higher costs and better reliability than a competing plan, thenot be practical. Therefore, selection of a particular plan cost difference to produce a particular increase in reliabilityis based partly on judgment as to the economic choice and will be of interest.partly on approximate cost comparisons.Capacitors are added if this will correct the overload, provided Applicationa specified maximum power factor is not exceeded. By The following sample problem should help clarify thespecifying several different values of maximum power factor, method of specifying the policies to be compared by thisthis model can determine the economical power factor limit. model.Load Transfers to specified adjacent substations are made,provided the transfer relieves the overloaded station for atleast 2 years without overloading the adjacent station or Assume that at present a distribution system consists ofstations. The planner must specify the adjacent sub- 138- to 34-kv T-S substations, a 34-ky subtransmissionstations, with or without priorities, to which load might be network, 34- to 4-kv S-D substations, and 4-kv distributiontransferred from each existing substation. The model at- feeders.tempts to transfer load in priority order, or, if no prioritiesare specified, to distribute the overload between any adjacentsubstations which have surplus capacity. If transfers from Three different plans to expand the system are to be com-several overloaded stations to the same receiving station will pared.overload the receiving station, the transfers are restricted to Plan I. Continue to expand the system with the same volt-prevent the overload. age levels. To establish this policy in the input data, theThe requirement that load transfers must provide relief for planner would specify which 138-34-kv and 34-4-kv sub-

    2 years serves to eliminate many minor transfers which are not stations could be expanded, where new 138-34-kv substationssignificant in lonig-range studies but which would add a con- could be located when needed, and the types of 34-4-kv sub-siderable amount of computer running time if included. stations to be installed as required.The adjacent subtations which are specified may include Plan II. Start using a new distribution voltage, 13.8 kv,

    those supplying higher distribution or subtransmission volt- and avoid the expansion or new installations of 138-34-kvages. Thus, the effect of transferring load directly to the stations by using 138-13-kv stations to supply the distribu-subtransmission voltage can be studied. tion load. The input would specify the location of new 138-Substation Expansions or New Substations are required if relief 13-kv substations, which could be installed as required, butis not provided by capacitors or transfers. If no priority of would not permit the expansion of the 138-34-kv stations.expansion or new substation is specified in the input data, the The 34-4-kv stations would be relieved as required by transfersmodel analyzes the area around the overloaded station and its to the 13.8-kv distribution, except in any particular areasadjacent stations and selects a tentative location for a new where such conversion is not considered feasible, so no 13-kvsubstation which could relieve the overloaded substation for source is specified. Special designs may be necessary to keepseveral years and also provide the maximum relief for other the same reliability level as Plan I and to keep short-circuitadjacent stations. The approximate unit costs of the sub- duties to values that can be interrupted by the distributiontransmission, substation, and distribution facilities to supply equipment.the load in the area from this new substation are compared Plavn III. Establish 34-ky as a distribution voltage andwith the costs of supplying the same load from the nearby avoid the installation of new 34-4-ky substations. The inputexisting substations which might be expanded. The plan would specify which 138-34-ky substations can be expandedwith the lowest costs is selected. and the possible locations of new substations of this type. The

    34-4-kv stations w-ould be relieved as required by transfers toReliability Sub-MVodel the 34-ky distribution-subtransmission lines. Special designsThe function of the Reliability Sub-Model is to calculate must also be incorporated to keep comparable reliability

    some quantitative measures of the continuity of service pro- levels and to maintain acceptable short-circuit duties.

    APRIL 1964 Lawrence, Montmeat, Patton, Wappler- Automated Distribution System 315

  • Conclusions ReferencesThe distribution system planning model described in this 1. DISTRIBUTION SYSTEM PLANNING THROUGH OPTIMIZED DE-SIGN.

    paper exlands the system step-by-step through time, starting II-COMPARATIVE ECONOMICS OF SYSTEM VOLTAGES, R. F. Law-rence, D. N. Reps, A. D. Patton. AIEE Transactions, pt. III (Powerwith the existing system, to discover the optimal strategies for Apparatus and Systems), vol. 79, June 1960, pp. 204-13.future distribution system expansion. Important questions 2. ECONOMIc ANALYSIS OF DISTRIBUTION SYSTEMS, H. E. Campbell,which cani be answered through the use of the model in- R. C. Ender, M. W. Gangel, W. C. Talley. Ibid., Aug. 1960, pp. 423-clude: 40.

    3. OPTIMIZED DISTRIBUTION AND SUBTRANSMISSION SYSTEM PLAN-1. What is the most economic combination of subtransmission NING BY DIGITAL COMPUTER. I-SYSTEM PHILOSOPHY, V. Con-and distribution voltages for future system expansion? verti, R. C. Ender, M. W. Gangel, R. E. Reinbold, P. E. Rist, N. R.2. VVhat are the most economic substation sizes and how should Schultz. See pp. 341-47 of this issue.substtations expand? 4. POWER SYSTEM RELIABILITY I-MEASURES OF RELIABILITY ANDMETHODS OF CALCULATION, D. P. Gaver, F. E. Montmeat, A. D.3. What is the most economic means of regulating voltage in the Patton. IEEE Transactions on Power Apparatus and Systems, vol. 83,system? 1964.4. How can desired reliability best be obtained in future sys- 5. SYSTEM PLANNING-PAST, PRESENT, AND FUTURE, J. K. Dillard,tems? H. K. Sels. Proceedings of the American Power Conference, Chicago,5. What is the impact on system economics of promotion and Ill., vol. 24, 1962.growth of new types of loads? 6. RESULTS OF A TWO-YEAR STUDY OF LONG-RANGE SYSTEM PLAN-NING BY SIMULATION, C. J. Baldwin, C. H. Hoffman. Proceedings of

    It is evident that a planning study using these automated the Nineteenth Convention of CIGRE, 1962, Paper No. 306.planning techniques requires a large amount of data. The 7. PRESENThWORTH APPROACH FOR OPTIMIZING DISTRIBUTIONTRANSFORMER AND SECONDARY DESIGNS TO SERVE GROWING LOADS,accumulation of required data iS difficult and time consuming, R. P. Burandt, J. A. Hughes, A. D. Patton, D. N. Reps. AIEEbut economies resulting from studies utilizing the data will Transactions, pt. III (Power Apparatus and Systems), vol. 80, Aug.justify the task. An important side benefit of the data- 1961, pp. 345-49.gathering process is the systemization of data needed for other 8. A GENERAL PROGRAM FOR PROCESSING DISTRIBUTION DATA,

    types of problems,suchas: raesandmarktreseareb G. P. Rhoten. Electrical World, New York, N. Y., vol. 156, Dec. 18,types of problems, such as: rates and market research, 1961, pp. 45-48.distribution transformer load management, feeder voltage 9. LAND-USE DATA IMPROVE LOAD FORECASTS, Americo Lazzari.drop, and load calculations. Ibid., vol. 157, June 18, 1962, pp. 38-40.

    Application of Digital Computer Techniques to theEconomic Scheduling of Marginal GeneratingUnits for the Pennsylvania-New Jersey-Maryland InterconnectionL. T. Anstine, Senior Member IEEE J. H. Henderson F. A. Kramer, Member IEEEF. H. Light, Senior Member IEEE G. A. Pall F. M. Reed, Senior Member IEEE H. G. Stewart, Member IEEE C. H. Wetter

    Economical power generation is the indispensable condition using a digital computer to select and determine the operatingof the successful operation of any electric utility company. hours of marginal steam units, thereby minimizing energyWhereas there are several areas of endeavor, where efforts production costs and, at the same time, meeting spinninghave been and are being made towards increased economy reserve capacity requirements on the Pennsylvania-Newand more effective utilization of equipment, the scheduling Jersey-Maryland Interconnection.of individual generating units on an optimum economy basis The basic requirements, operational rules, and technicalhas always been one major factor in the over-all effort. specifications, which are introduced into the schedulingThis paper reports on an investigation of the feasibility of technique as constraints and/or variables, were originally

    defined by a Pennsylvania-New Jersey-Maryland Inter-Paper 63-1405, recomnmended by the IEEE Power System Engi- .

    b

    neering Committee and approved by the IEEE Technical Operations connection Task Force on Automatic Load Control. TheComlnittee for presentation at the IEEE-ASME National Power International Business Machines Corporation assisted in theConlference, Cincinnati, Ohio, September 22-26, 1963. Manuscript development of the computer program and techniques forsubmitted June 3, 1963; made available for printing August 20, 1963.L. T. ANSTINE is with the Baltimore Gas and Electric Company, obann th deie rsl.Baltimore, Md.; J. H. HENDERSON i5 with the Pennsylvania Power The system studied for application of digital computerand Light Company, Hazleton, Pa.; F. A. KRAMER and C. H. techniques in scheduling has an installed capacity of approxi-WETTER are with the Public Service Electric and Gas Company, mately, 16,000 megawatts, distributed among approximatelyNewark, N.J.; F. 11. LIGHT is with the Philadelphia Electric Com- .'pany, Philadelphia, Pa.; G. A. PALLis with the International Business 300 units, and a peak-hour integrated load of about 13,000Machlines Corporation, also in Philadelphia; F. M. REED is with the megawatt-hours. The interconnecting transmission be-General Public Utilities System, Reading, Pa., and H. G. STEWART tween the member companies is of sufficient capacity so thatis with the Pennsylvania-Newv Jersey-Maryland Interconnection, thcaciynayprtotessem angealybPhiladelphia, Pa.th aatynanpatoth sytmcngerlyb

    316 Anstinwe, Henderson, Kramer, Ligsht, Pall, Reed, Stewart, Wetter-Computer Techniques APRIL 1964

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