某110kv变电站短路电流计算书.doc

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1、一、短路电流计算取基准容量Sj=100MVA，略去“*”，Uj=115KV，Ij=0.502A富兴变：地区电网电抗X1=Sj/Sdx=Ij/Idx=0.502/15.94=0.0315km线路电抗X2=X*L*(Sj/Up2)=0.4*5*(100/1152)=0.015发电机电抗X3=(Xd’’%/100)*(Sj/Seb)=(24.6/100)*(100/48)=0.51216km线路电抗X4=X*L*(Sj/Up2)=0.4*16*(100/1152)=0.0495.6km线路电抗X5=X*L*(Sj/Up2)=0.4*5.6*(100/1152)=0.01731.5MVA变压器电抗

2、X6=X7=(Ud%/100)*(Sj/Seb)=(10.5/100)*(100/31.5)=0.33350MVA变压器电抗X=(Ud%/100)*(Sj/Seb)=0.272X8=X3+X4+X5=0.578X9=X1+X2=0.046X10=(X8*X9)/(X8+X9)X11=X10+X6=0.046地区电网支路的分布系数C1=X10/X9=0.935发电机支路的分布系数C2=X10/X8=0.074则X13=X11/C1=0.376/0.935=0.402X14=X11/C2=0.376/0.074=5.081、求d1’点的短路电流1.1求富兴变供给d1’点(即d1点)的短路电流I

3、x″=Ij/(X1+X2)=0.502/(0.031+0.015)=10.913kASx″=Sj/(X1+X2)=100/(0.031+0.015)≈2173.913MVAichx1=√2*Kch*Ix″=√2*1.8*10.913=27.776kAIch=Ix″√1+2(Kch-1)2=10.913*√1+2(1.8-1)2=10.913*1.51=16.479kA1.2求沙县城关水电站供给d1’点的短路电流将发电机支路的等值电抗换算到以发电机容量为基准容量时的标幺值Xjs=X8*Srg/Sj=0.578*48/100=0.277查表得I*’’=3.993I*0.2=3.096I*4=3

4、.043换算到115kV下发电机的额定电流:Ief=Srg/(3Up)=48/(1.732x115)=0.241求得:If’’=I*’’*Ief=3.993x0.241=0.962kAIf0.2’’=I*0.2’’*Ief=3.096x0.241=0.746kAIf0.4’’=I*4’’*Ief=3.043x0.241=0.732kAichf=√2*Kch*If″=√2*1.8*0.962=2.448kA1.3求得d1’点的短路电流Ix″=10.913+0.962=11.875kAich=27.776+2.448=30.224kAIch=11.875√1+2*(1.8-1)2=17.93k

5、A2、求d2点的短路电流Ix″=Ij/(X1+X2+X6)=5.50/(0.031+0.015+0.333)=14.512kAichx=2*Kch*Ix2″=2*1.8*14.512=36.936kAIch=Ix″√1+2(Kch-1)2=14.512*√1+2(1.8-1)2=21.913kA3、求d2’点的短路电流3.1求富兴变供给d2’点的短路电流Ix″=Ij/X13=5.5/0.402=13.68kAichx1=√2*Kch*Ix″=√2*1.8*13.68=34.82kAIch=Ix″√1+2(Kch-1)2=13.68*√1+2(1.8-1)2=20.656kA3.2求沙县城关

6、水电站供给d2’点的短路电流将X14换算到以发电机容量为基准容量时的标幺值Xjs=X14*Srg/Sj=5.08*48/100=2.438查表得I*’’=0.425I*0.2=0.431I*4=0.431换算到115kV下发电机的额定电流:Ief=Srg/(3Up)=48/(1.732x10.5)=2.64求得:If’’=I*’’*Ief=0.425x2.64=1.122kAIf0.2’’=I*0.2’’*Ief=0.431x2.64=1.138If4’’=I4’’*Ief=0.431x2.64=1.138kA3.3求得d2’点的短路电流Ix″=13.68+1.122=14.802kAic

7、h=1.414x1.8x14.802=37.674kAIch=14.802√1+2*(1.8-1)2=22.35kA同理：求得终期d2点的短路电流Ix2″=Ij/(X1+X2+X6)=5.50/(0.031+0.015+0.272)=17.3kAichx=√2*1.8*17.3≈44kAIch=Ix″*√1+2(Kch-1)2=17.3*√1+1.28=26.122kA求得终期d2’点的短路电流Ix″=16.32+1.3