ABB RER670 - Page 184

Substation A
Substation B
Z
lineAB,1
(pos. seq)
Z
lineAB,0
(zero seq)
Z
lineBC,1
(pos. seq)
Z
lineBC,0
(zero seq)
U
0A
U
0B
2I
0
Phase to earth fault
R
N
Z
T,1
(pos. seq)
Z
T,0
(zero seq)
Source impedance
Z
sc
(pos. seq)
IEC16000126-1-en.vsdx
IEC16000126 V1 EN-US
Figure 58: Equivalent of power system for calculation of setting
The residual fault current can be written:
0
10
2
2
22
phase
f
U
I
ZZ R

 
IECEQUATION16034 V1 EN-US (Equation 47)
Where
U
phase
is the phase voltage in the fault point before the fault
Z
1
is the total positive sequence impedance to the fault point. Z
1
= Z
sc
+Z
T,1
+Z
lineAB,1
+Z
lineBC,1
Z
0
is the total zero sequence impedance to the fault point. Z
0
= Z
T,0
+2R
N
+Z
lineAB,0
+Z
lineBC,0
R
f
is the fault resistance.
The residual voltages in stations A and B can be written:


00,0
22
A
TN
UIZR 
IECEQUATION16097 V1 EN-US (Equation 48)


0 0 ,0 ,0
22
B T N lineAB
UIZRZ  
IECEQUATION16098 V1 EN-US (Equation 49)
Section 8 1MRK 506 375-UEN A
Current protection
178 Railway application RER670 2.2 IEC
Application manual