继电保护计算课本

电网参数的整理与计算

在本章中，所有的计算均采用近似算法。

s b=100MV A u b= u av =115KV Z b= u b2/s b=1152/100 =132.25

第1.1节计算系统中各元件的主要参数

1.1.1 发电机的参数

（1）算法

标幺值：x g* = x d’’s b/s n

有名值：x g = x d’’u n2/s n

（2）A厂发电机参数

已知p n =25MW cosφ(A) =0.8 x d’’ (A) =0.165 u n(A) =6KV

s n (A)= p n(A)/cosφ(A) =25/0.8 = 31.25 MV A

x g(A) * = x d’’ (A) s b/ s n (A) = 0.165*100/31.25 =0.528

x g(A) = x g(A) * Z b =0.528*132.25 = 69.828Ω

（3）B厂发电机参数

已知p n(B) =6 MW cosφ(B) =0.8 x d’’ (B) =0.122 u n(B) =6KV

s n (B)= p n(B)/cosφ(B) = 6/0.8 = 7.5 MV A

x g(B) * = x d’’ (B) s b/ s n (B) =0.122*100/7.5 =1.627

x g(B) = x g(B) * Z b =1.627*132.25 = 215.127Ω

1.1.2变压器的参数

（1）算法

标幺值：x T* = u K% s b/(100 s n)

有名值：x T*=u K%u n2/(100 s n)

（2）A厂变压器参数

已知：s nA =31.5 MV A u K% =10.5 u n =115kv

则x T（A）*=u K% s b/(100 s nA) =10.5⨯100/（100⨯31.5）=0.333

x T（A）= u K%u n2/(100 s nA) =10.5⨯1152/（100⨯31.5）= 44.083Ω（3）B厂变压器参数

已知：s nB =15 MV A u K% =10.5 u n =115 kv

则x T（B）*=u K% s b/(100 s nB) =10.5⨯100/（100⨯15）=0.7

x T（B）= u K%u n2/(100 s nB) =10.5⨯1152/（100⨯15）= 92.575Ω

（4）C厂变压器参数

已知：s nC =31.5 MV A u K% =10.5 u n =115 kv

则x T（C）*=u K% s b/(100 s nC) =10.5⨯100/（100⨯31.5）=0.333

x T（C）= u K%u n2/(100 s nC) =10.5⨯1152/（100⨯31.5）= 44.083Ω1.1.3 线路的参数

已知：LGJ—185型导线D m =4.5m

r1 =0.17Ω/km x1 =0.4Ω/km r0 =0.51Ω/km x0 =1.21Ω/km

l AC =35km l BC =43km l AB =65km

（1）AC的参数

有名值：R AC1= r1 l AC =0.17⨯35 =5.95ΩX AC1= x1 l AC =0.4⨯35 =14Ω

R AC0= r0 l AC =0.51⨯35 =17.85ΩX AC0= x0 l AC =1.21⨯35 =42.35Ω则Z AC1= R AC1+ jX AC1=5.95 + j14 = 15.212︒

∠67Ω

Z AC0= R AC0+ jX AC0=17.85 + j42.35 = 45.958︒

∠67Ω

标幺值：Z AC1*= Z AC1/ Z b=5.95 + j14 /132.25 =0.045 +j0.106 =0.115︒

∠67

Z AC0*= Z AC0/ Z b=17.85 + j42.35 /132.25 =0.135 +j0.32 =0.347︒

∠67（2）路BC的参数

有名值：R BC1= r1 l BC =0.17⨯43 =7.31ΩX BC1= x1 l BC =0.4⨯43 =17.2ΩR BC0= r0 l BC =0.51⨯43 =21.93ΩX BC0= x0 l BC =1.21⨯43 =52.03Ω则Z BC1= R BC1+ j X BC1=7.31+ j17.2= 18.69︒

∠67Ω

Z BC0= R BC0+ j X BC0=21.93 + j52.03 = 56.46︒

∠67Ω

标幺值：Z BC1*= Z BC1/ Z b=7.31 + j17.2/132.25 =0.055 +j0.13 =0.115︒

∠67 Z BC0*= Z BC0/ Z b=21.93 + j52.03 /132.25 =0.166 +j0.393=0.427︒

∠67（3）线路AB的参数

有名值：R AB1= r1 l AB =0.17⨯65=11.05ΩX AB1= x1 l AB =0.4⨯65 =26ΩR AB0= r0 l AB =0.51⨯65 =33.15ΩX AB0= x0 l AB =1.21⨯65 =78.65Ω则Z AB1= R AB1+ jX AB1=11.05 + j26 = 28.25︒

∠67Ω

Z AB0= R AB0+ jX AB0=33.15+ j78.65= 85.35︒

∠67Ω

标幺值：Z AB1*= Z AB1/ Z b=11.05+ j26 /132.25 =0.083 +j0.197=0.214︒

∠67 Z AB0*= Z AB0/ Z b=33.15 + j78.65/132.25 =0.251 +j0.595 =0.646︒

∠67