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2-17某机修车间，装有冷加工机床56台，共260kW；行车1台，共5.1kW，FC＝15％；通风机4台，共5kW；点焊机3台，共10.5kW，FC＝66％。该车间采用380／220V供电，试确定该车间的计算负荷(PC、QC、SC、IC)。解：由题可知，查p220附表2冷加工机床Kd1=0.15Pc1=PN1Kd1=260×0.15=39kW行车Kd2=0.10Pc2=PN2Kd2FC=5.1×0.1×15.0=0.1975kW通风机Kd3=0.80Pc3=PN3Kd3=5×0.8=4kW点焊机Kd4=0.35Pc4=PN4Kd4FC=10.5×0.35×66.0=2.9856kW同理tanφ1=1.73Qc1=Pc1tanφ1=39×1.73=67.47kvartanφ2=1.73Qc2=Pc2tanφ2=0.1975×1.73=0.3417kvartanφ3=0.70Qc3=Pc3tanφ3=4×0.7=2.8kvartanφ1=1.33Qc4=Pc4tanφ4=2.9856×1.33=3.9708kvarPc=Pc1+Pc2+Pc3+Pc4=39+0.1975+4+2.9856=46.1831kWQc=Qc1+Qc2+Qc3+Qc4=67.47+0.3417+2.8+3.9708=74.5825kvar7236.87432.76955825.741831.462222CCCQPSkVA2861.13338.037236.873NCCUSIA2-20某工厂35kV总降压变电所，拟选用两台等容量变压器，已知工厂总计算负荷为5000kV·A，其中一、二级负荷容量为3000kV·A，试选择变压器的容量。解：由题意，按暗备用方式3500%705000(kV·A)查p222附表4，试选择2台SL7-3150/35或SL7-4000/35则校验，(1)正常运行时%37.7931502/5000不符合经济运行要求%5.6240002/5000符合经济运行要求(2)事故情况下，满足过负荷能力首先3150和4000都大于3000kV·A，满足一二级负荷需要。4410%1403150kV·A负荷能力%2.8850004410，基本满足过负荷要求5600%1404000kV·A负荷能力%11250005600，满足过负荷要求综上所述，可选择2台SL7-4000/35型变压器。2-22某架空线路为8.2km，输电电压为35kV，导线型号为LJ-95，供电给某用户，年耗电量W＝14980×103kW·h，线路上的最大负荷电流Ifmax＝128A，cosφ=0.85，试求该线路上的功率损耗及年电能损耗。解：由题意，最大功率Pm65.659585.0128353cos3maxIUPNmkW则19.227165.6595/1014980/3maxmnPWTh查p53图2-46，可得τ=1550h由p226附表11查得r0=0.34Ω/km，x=0.36Ω/km得R=0.34×8.2=2.788Ω，X=0.36×8.2=2.952Ω年电能损耗41.212101550788.212831033232RIWClkW·h功率损耗6197.01)cos1(cos22222PPPPPSQ单位时间功率P=Wn/8760=14980MW·h/8760h=1.71MWQ=0.6197P=0.6197×1.71=1.0597Mvar则MVAMVAjjjXRUQPSL64.460134141.0)00975.000921.0()952.2788.2(3505972.171.1)(222222全年功率损耗=0.0134141×8760=117.51MVA3-11供电系统如图3-20所示，试求图中k1、k2点发生三相短路时的短路参数(Ik(3)、I∞(3)、ish(3)、Sk(3))以及在最小运行方式下k2点的两相短路电流Ik(2)。解：由题意，选Sj=100MVA，Uj1=Uj2=6.3kV，则kAIIjj16.93.6310021(1)各元件阻抗标幺值4.0250100)3(max.*1kjMSSX，5051.0198100)3(min.*1kjmSSX1461.03710054.0221101*2avjUSlxX75.0101001005.7100%*3NTjkSSuX1638.13.61003.03610043100%222..*4avjLRNLRNLRUSIUXX1612.03.61008.008.0222202*5avjUSlxX(2)求电源点至短路点的总阻抗k1(3)点2961.175.01461.04.0*3*2*1*.1XXXXMM4012.175.01461.05051.0*3*2*1*.1XXXXmm(3)求短路电流最大运行方式：7715.02961.111*.1)*3(.1MMzXIkAIIIjMzMz0674.716.97715.0)*3(.1)3(.1kAIiMzMsh0218.180674.755.255.2)3(.1)3(.1kAiIMshMsh6891.10686.1)3(.1)3(.1MVASISjMzMk15.771007715.0)*3(.1)3(.1最小运行方式：7137.04012.111*.1)*3(.1mmzXIkAImz5373.616.97137.0)3(.1k2(3)点6211.21612.01638.12961.1*5*4*.1*.2XXXXMM7262.21612.01638.14012.1*5*4*.1*.2XXXXmm3815.06211.211*.2)*3(.2MMzXIkAIIIjMzMz4947.316.93815.0)*3(.2)3(.2kAIiMzMsh9115.84947.355.255.2)3(.2)3(.2kAiIMshMsh2856.5686.1)3(.2)3(.2MVASISjMzMk15.381003815.0)*3(.2)3(.2最小运行方式：3668.07262.211*.2)*3(.2mmzXIkAImz36.316.93668.0)3(.2kAIImzmz9098.236.32323)3(.2)2(.23-12某供电系统如图3-21所示，图中各条线路参数均相同，若要求k点发生三相短路时最大冲击电流不超过20kA，试问1)能否将母联开关QF闭合长期并联运行？2)最多允许几根电缆并联运行？解：由题意，选Sj=100MVA，Uj=Uav=6.3kV，则kAIj1646.93.63100各元件阻抗标幺值7456.13.61002.03610043100%222..*avjLRNLRNLRLRUSIUXX3137.03.61005.1083.0220*avjUSlxX3983.13.61005.137.02220*avjUSlrR则4331.13137.03983.1222*2**XRZ1787.34331.17456.1***ZXZLR2条并联5894.121787.32**)2(ZZ3条并联0596.131787.33**)3(ZZ4条并联7947.041787.34**)4(ZZ有6292.01*)2(*)2(ZIkAIIijsh7035.146292.01646.955.255.2*)2()2(9438.01*)3(*)3(ZIkAIIijsh0552.229438.01646.955.255.2*)3()3(2583.11*)4(*)4(ZIkAIIijsh407.292583.11646.955.255.2*)4()4(结论：1)不能将母联开关QF闭合长期并联运行；2)最多允许2根电缆并联运行。