ABB RELION RET670 - Page 566

Substation A
Substation B
Z
lineAB,1
(pos. seq)
Z
lineAB,0
(zero seq)
Z
lineBC,1
(pos. seq)
Z
lineBC,0
(zero seq)
V
0A
V
0B
3I
0
Phase to ground fault
R
N
Z
T,1
(pos. seq)
Z
T,0
(zero seq)
Source impedance
Z
sc
(pos. seq)
en06000654_ansi.vsd
ANSI06000654 V1 EN-US
Figure 278: Equivalent of power system for calculation of setting
The residual fault current can be written:
phase
0
1 0 f
3V
3I
2 Z Z 3 R
=
× + + ×
EQUATION2023-ANSI V1 EN-US (Equation 440)
Where
V
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
+3R
N
+Z
lineAB,0
+Z
lineBC,0
R
f
is the fault resistance.
The residual voltages in stations A and B can be written:
Section 9 1MRK 504 163-UUS A
Current protection
560 Transformer protection RET670 2.2 ANSI
Application manual