虎石台220 60KV降压变电所电气部分初步设计 计算书.doc

第一章短路电流的计算

取SB = 100MVA,VB = Up,求得等值电路图中各阻抗标幺值如下:
发电机1:X2 = X4 = Ud%/100×SB/S = ×100/200/ =
变压器1:X3 = X5 = Xd%/100×SB/S = 14/100×100/240 =
发电机2:X6 = X8 = X10= Ud%/100×SB/S = 18/100×100/125/ =
变压器:X7 = X9 = X11 = Xd%/100×SB/S = =
线路:2×100KM: X’= 1/2×100××100/2202 =
60KM: X”= 60××100/2202 =
X1 = X + X = + =
48KM线路: X12 = 48××100/2202 =
2×60KM线路: X13 = 1/2×60××100/2202 =
2×100KM线路: X14 = 160××100/2202 =
80KM线路: X15 = 80××100/2202 =
220KV母线上K1点发生短路时的短路计算
首先进行网络化简,化简后的网络图见图:
X‘1 = X* + X1 = + =
X‘2 =(X2 + X3)/2 =( + )=
X‘3 = (X6 + X7)/3 =( + )/3 =
X‘4 = X12 = X‘5 = X13 =
X‘6 = X15 = X‘7 = X14 =
进一步化简如下:
对X’5 X’6 X’7 进行三角变换
网络见图1-4所示
X”1 = X’5X’7/(X’5 + X’6 + X’7)
= ×/( + + ) =
X”2 = X’6X’7/(X’5 + X’6 + X’7)
= ×/( + + ) =
X”3 = X’5X’6/(X’5 + X’6 + X’7)
= ×/( + + ) =
网络见图1-5所示
X ‘= X1X2/X1 +X2 = ×/( + )=
X“= (X‘+ X3)X4/(X‘+ X3 + X4)
=( + )×/( + + )
=
X# = X ‘+ X”= + =
C3 = X”/(X’+ X3) = /( + )=
C4 = 1 - C3 = 1 - =
C1 = C3 X’/X1 = × =
C2 = C3 - C1 = - =
X∈=
X1∈= X∈/C1 = =
X2∈= X∈/C2 = =
X4∈= X∈/C4 = =
Xjs1 = X1∈SG1/SB = ×11000/100 =
Xjs2 = X2∈SG2/SB = ×200/ =
Xjs4 = X4∈SG3/SB = ×125/ =
X‘∈= X∈+ 1/2×(Ud%/100)×(100/S变)
= +(1/2)×()×(100/120000)
=
X‘1∈= X‘∈/C1 = =
X‘2∈= X‘∈/C2 =