ABB RELION 670 Series Applications Manual page 136

Section 8
Current protection
Z (pos. seq)
T,1
Z (zero seq)
T,0
Phase to ground fault
ANSI06000654 V1 EN-US
Figure 57: Equivalent of power system for calculation of setting
The residual fault current can be written:
=
3I
0
2 Z
EQUATION2023-ANSI V1 EN-US
Where
V
phase
Z
1
Z
0
R
f
The residual voltages in stations A and B can be written:
=
V 3I (Z
0 A
EQUATION2024-ANSI V1 EN-US
130
Source impedance
Z (pos. seq)
sc
R
V
0A
3I
0
Z (pos. seq)
lineAB,1
Z (zero seq)
lineAB,0
V
0B
Z (pos. seq)
lineBC,1
Z (zero seq)
lineBC,0
en06000654_ansi.vsd
3V
phase
× + + ×
Z 3 R
1 0 f
is the phase voltage in the fault point before the fault
is the total positive sequence impedance to the fault point. Z
is the total zero sequence impedance to the fault point. Z
is the fault resistance.
× +
3R )
0 T ,0 N
N
Substation A
Substation B
0
= Z +Z +Z +Z
1 sc T,1 lineAB,1 lineBC,1
= Z +3R +Z +Z
T,0 N lineAB,0 lineBC,0
1MRK 511 364-UUS A
(Equation 44)
(Equation 45)
Application manual