線路參數測試的實用優化方案APracticalOptimizedMethodofCircuitParameterTest兩個及以上T接點的聯絡線如圖2~4，在計算220kVA變電站516斷路器保護時，需要測試A-b、A-c、（A-d）、（A-e）、A-F線路的阻抗值；在計算220kVF變電站504斷路器保護時，需要測試F-c、F-b、（F-d）、（F-e）、F-A線路的阻抗值。通過分析線路阻抗的理論值，在對線路電源端的220kVA站和F站的斷路器繼電保護進行計算時，為保證距離、零序Ⅰ段不伸入下級變電站主變，選擇正序、零序阻抗最小的某段線路如A-b和F-c進行計算；為保證距離、零序Ⅱ段對全線有靈敏度，選擇正序、零序阻抗最大的線路如A-c和F-b或A-F進行計算。通過分析，對線路參數測試方案進行如下優化：選擇阻抗值最小和最大的A-b、F-c、A-c、F-b或A-b、F-c、A-F進行參數測試。測試次數由5至9次減少到3至4次。ThewiresofTwoormoreTconnectionpointsareshowninfigure2~4.Whentheprotectionof516circuitbreakerofthe220kVAtransformersubstationiscomputed,theimpedancecircuitsofwireA-b,A-c,(A-d),(A-e),andA-Fshouldbetested.Whentheprotectionof504circuitbreakerofthe220kVFtransformersubstationiscomputed,theimpedancecircuitsofwireF-c,F-b,(F-d),(F-e),andF-Ashouldbetested.Throughanalyzingthetheoreticalvalueoflineimpedance,aconclusioncanbedrawn:when220kVAand220kVFtransformersubstationsatthepowerportofthecircuitarecomputed,inordertoensurethedistanceandthesectionⅠofzerosequenceshouldnotstretchintotheinferiortransformersubstation’smaintransformer,andthewire(likewireA-bandF-c)whichhastheminimumimpedanceofpositivesequenceaswellaszerosequenceshouldbecomputed.What’smore,tomakesurethedistanceandthesectionⅡofzerosequencehavesensitivitiestowardthewholewires,thewire(likewireF-bandA-F)whichhasthemaximumimpedanceofpositivesequenceandzerosequenceshouldbecomputed.Accordingtotheanalysis,thetestingmethodoflineparameterscanbeoptimizedasfollows:choosetheminimumimpedanceandmaximumimpedance(likewireA-b,F-c,A-c,F-borwireA-b,F-c,A-F)todotheparametertest.Thenumberoftestingshouldreducedto3~4timesfrom5~9times.4．實例分析InstanceAnalysis以長沙電網110kV榔農合黎Ⅰ線線路為例，對線路參數測試的實用優化方案進行驗證。ToverifythepracticaloptimizedmethodoftheCircuitparametertest,heretake110kVLangNongHeLiLineⅠofChangshapowergridasanexample.2012年07月，110kV榔農合黎Ⅰ線桿遷，送電前進行參數測試。該線路為兩個T接點，架空和電纜混合的輸電線路。測試出的線路阻抗值與理論值比較見表1。InJuly,2012,becauseofbeingremoved,110kVLangNongHeLiLineⅠwasconductedtheparametertestbeforethepowertransmission.ThelinehadtwoTcontact,namely,overheadandcablehybridtransmissionlines.Thetestedimpedancevalueanditstheoreticalvaluearecomparedintable1.表1榔農合黎Ⅰ線理論值與實測值的比較Table1:ThecomparisonbetweenthetheoreticalimpedancevalueandthetestedimpedancevalueoftheLangNongHeLiLineⅠ榔農合黎Ⅰ線有名值R1X1R0X0Z1(Ω)Z1角度Z0(Ω)Z0角度榔農段理論值1.08193.40203.240810.21153.5772.3610.7172.40榔農段實測值0.98363.30703.17879.78523.4573.5010.2972.00榔合段理論值1.44913.56603.592710.70953.8567.8911.3071.50榔合段實測值1.35463.38713.486110.63603.6568.2111.1971.86榔黎段理論值1.52235.01435.158214.71285.2471.7915.5970.68榔黎段實測值1.39054.54554.225313.68104.7673.0514.3272.84黎合段理論值0.80931.67301.66785.03651.8664.195.3168.91黎合段實測值0.47281.62661.86335.16351.7073.845.4970.16黎農段理論值1.13053.59543.381310.79763.7772.5511.3271.74黎農段實測值0.94273.41693.198510.28473.5471.4410.7769.83在計算榔梨變514、黎托變522斷路器保護時，根據Ⅰ段不伸入下級主變，Ⅱ段對全線有靈敏度的原則，重點考慮離兩個220kV榔梨、黎托變阻抗最小和阻抗最大的站之間進行實測，從表1可見，與榔梨變阻抗最小和阻抗最大的為榔農段和榔黎段，與黎托變阻抗最小和阻抗最大的為黎合段和榔黎段，通過分析，可對參數實測方案進行優化，采取榔梨變至農大變、榔梨變至黎托變、黎托變至合豐變各實測一次的方案，測試次數可由原5次減少為3次，減少2次。Basedontheprinciplesthat“sectionⅠshouldnotstretchintotheinferiormaintransformer”and“thesectionⅡhassensitivitiestowardthewholewire”,whencomputingprotectionoftheLanglitransformersubstation514breakerandLangtuotransformersubstation522breaker,weshouldmainlyconsidertestingthestationswhichhavethemaximumortheminimumimpedanceoftheLanglitransformersubstationandLangtuotransformersubstation.Fromtable1,theLangnongsegmenthastheminimumimpedanceandtheLanglisegmenthasthemaximumimpedancewithLanglitransformersubstation.Besides,theLihesegmenthastheminimumimpedanceandtheLanglisegmenthasthemaximumimpedancewithLangtuotransformersubstation.Throughanalyzing,wecanoptimizetheparametermeasurementmethodbytestingthefollowingsectionsonce:thesectionfromLanglitransformersubstationtoNongdatransformersubstation,thesectionfromLanglitransformersubstationtoLituotransformersubstationandthesectionfromLituotransformersubstationtoHefengtransformersubstation.Thetestingtimescanbedroppeddownfrom5to3,thatis,reducedfor2times.從表1該線路理論值與實測值的比較來看，正序、零序阻抗理論值與實測值趨勢一致，理論值與實測值的差距在選取最大最小值時可忽略。省略榔合段與黎農段的實測后，優化后測試出的線路阻抗同樣完全滿足保護計算的需求。通過對110kV電網多T接、多段架空和電纜混合輸電線路參數測試的實例證明，本文提出的實用優化方案是切實可行的。Accordingtothecomparisonbetweenthecircuit’stheoreticalimpedancevalueandtestedimpedancevalueinthetable1,thetrendoftheoreticalvalueandthetestedvalueofthepositivesequenceandzerosequenceimpedanceisconsistent,andthedifferencesbetweenthetheoreticalvalueandthetestedvaluecanbeignoredwhenthemaximumorminimumvalueisbeingchosen.AfteromittingthetestofLangheandLinongsegments,thecircuitimpedances,whicharetestedinaoptimizedsituation,canalsofullymeettheneedsofthecalculationoftheprotection.Fromthisinstance,wecansafelydrawaconclusionthattheoptimizedmethodispracticable.5．效益分析BenefitAnalysis1）經濟效益EconomicBenefit按實測一次需費用2萬元，需耗時2小時計算，采用本文提出的優化方法測試參數，雙T線路減測2次，每條線路可節省費用2萬元×2=4萬元，節省耗時4小時。三T線路減測3次，每條線路可節省費用2萬元×3=6萬元，節省耗時6小時。四T線路減測6次，每條線路可節省費用2萬元×6=12萬元，節省耗時12小時。參數測試方案的優化縮短了線路停電時間，每條線路節省4~12小時，極大降低了電網風險，其安全效益不可估量；每條線路節省4~12萬元測試費用，大大節約測試成本，其經濟效益非常可觀。Accordingtothecondition--eachtestcosts20,000yuanand2hours--tocalculatetheexpenses,theoptimizedmethod(whichismentionedinthisthesis)willbebeneficialifitisappliedtotestthecircuitparameter.Forexample,forthedoubleTcircuit,thetestingwillbecutfor2times,so40,000yuanand4hourswillbesavedineachcircuit;forthetripleTcircuit,thetestingwillbecutfor3times,so60,000yuanand6hourswillbesaved;forthequadrupleTcircuit,thetestingwillbecutfor6times,so120,000yuanand12hourswillbesaved.Theoptimizationofparametertestingmethodcutsdownthecircuitoutagetimeandsaves4~12hoursaswellas40,000~120,000yuanforeachcircuit,soitnotonlyreducestheriskinpowergridbutalsolowersthetestingcost.Withnodoubt,thisoptimizedmethodcanbringasoundedbenefitineconomy.（2）社會效益SocialBenefit按110千伏輸電線路停電對1000個用戶造成停電風險計算，采用本項目提出的優化方法測試線路參數，一條線路減少停電6小時，可減少6000個時戶數，即增加用戶供電可靠性0.004個百分點。按20條線路計算，增加用戶供電可靠性0.08個百分點，大大降低了用戶的停電風險，提高了供電可靠性.Accordingtothecondition--a110KVtransmissionline’smalfunctionwouldcauserisksto1,000users--tocalculate,theoptimizedmethodwillbesafeifitisappliedtotestthecircuitparameter.Forthismethod,6hours’powerfailureand6,000xxxwillbereduced,whichmeansthereliabilityofpowersupplywillbeimprovedfor0.004%.Ifthereare20circuits,theoptimizedmethodwillincrease0.08%powersupplyaswellasreducetheris