ABB RELION 670 SERIES Applications Manual page 171

1MRK 506 369-UUS -
Line distance protection REL670 2.2 ANSI
Application manual
A
21
ANSI05000221 V1 EN
Figure 61: Class 1, parallel line in service
The equivalent circuit of the lines can be simplified, as shown in figure 62.
Z0
A
Z0
B
IEC99000038 V1 EN
Figure 62: Equivalent zero sequence impedance circuit of the double-circuit,
parallel, operating line with a single phase-to-ground-fault at the remote
busbar
When mutual coupling is introduced, the voltage at the IED point A is changed, according
to equation 31.
æ
= × +
V Z 1 I 3 I
ç
ph 0
ph L
è
EQUATION1276 V4 EN
By dividing equation 31
impedance present to the IED at A side as:
æ
×
3 0 I
= +
Z Z 1 1
ç
L
+
I ph 3 0
è
EQUATION1277 V3 EN
FAULT
Z0m
-
Z0
m
Z0 m
-
Z0
m
-
Z 0 Z 1 Z
× +
L L 3 I
0 p
×
3 Z 1 3
L
by equation 30 and after some simplification we can write the
ö
KNm
÷
×
I KN
ø
Impedance protection
B
21
en05000221_ansi.vsd
C
99000038.vsd
ö
0
m
÷
×
Z 1
ø
L
Section 8
(Equation 31)
(Equation 32)
165