A Probability MethodforDetermining theReliability ofElectric PowerSystems

Thereciprocal ofm istheaverage rateoffa.ilure X. Similarly, iftheduration ofeachoutage isobserved andaveraged overalarge numberoffailures, aconstant average outage Reliability istheprobability ofsuccessful operation. The timerisfound.Thereciprocal ofristheaverage rateof accepted methodofexpressing component reliability isin repair ,u. terms ofanaverage timebetween failures m andanaverage A plotofthefailure rateXversus thecomponent ageis repair timer.Several booksandpapers describe thetech- called thelife characteristic (see Fig. 2).Thegraph hasthree niques ofmeasuring these parameters.'-3 A brief summary distinct parts. Whenthecomponent isnew,ithasahighbut isgiven hereinAp)pendix t,whichisbasedonBlazovsky's decreasing failure rate duetoerrors inmanufacturing which material.' areweededoutandstructurally defective parts whichfail Acurrent problem involves waystousethebasic componentearly. Whenthecomponent operates asdesigned, thefailure parameters tofind thereliability ofamulticomponent system. rate isrelatively small; italso isconstant, because failures are Operations research methods suchasMonteCarlo techniquescaused byfactors independent ofcomponent age.Foran andMarkovanalysis provide powerful tools forasolution.4 electric powersystem, someexamples ofchance happenings Forpowersystems, mostoftheprevious workhasdealt with whichhaveaconstant rate ofoccurrence arelightning, autogeneration planning."e Relatively fewpeoplehaveat- mobile accidents, falling trees, andanimals. Eventually the temipted toevaluate thereliability oftransmission and component starts towearout,andthefailure ratebegins distribution networks. Thispaper will beconcerned withthe torise. latter problem. Powerequipment isthoroughly tested inorder toeliminate Indeveloping amethod fordetermining network reliability, anycomponents withmanufacturing defects. Thistesting this paperdiscusses thememoryless system oftheMarkov program eliminates ahighinitial failure rate whentheequipprocess, theBoolean description ofnetwork configuration, the mentisfirst installed. Allelectric powercompanies periodMarkovequations, analytical solutions forthree simple sys- ically inspect andmaintain their equipment, eliminating or tems, andasimulation lprocess forthesolving ofthecomplex replacing equipment before itwears out.Thus,failures are systems. primarily duetochance a]one, andthefailure rate isaconstant Thepaperdoesnotdiscuss techniques fordeterminingwhichisindependent ofthesystem's pasthistory. Furtherwhether ornotanoutage ofagiven element orcombinationmore,therepair ratecanalsobeassumed tobeahistoryofelements inacomplex system results inaservice inter- independent constant. Thisbehavior describes a"memoryruption toanyspecific load.Available computer ornetwork less" system. analyzer techniques canbeusedtodetermine failure combina