ABB RED670 Handbuch Seite 202

Abschnitt 4
IED Anwendung
198
Where:
Vph is phase to earth voltage at the relay point
Iph is phase current in the faulty phase
3I0 is earth fault current
Z1 is positive sequence impedance
Z0 is zero sequence impedance
A
IEC05000221 V1 DE
Abb. 87: Class 1, parallel line in service.
The equivalent circuit of the lines can be simplified, see figure 88.
Z0
A
Z0
B
IEC99000038 V1 DE
Abb. 88: Equivalent zero sequence impedance circuit of the double-circuit,
parallel, operating line with a single phase-to-earth fault at the
remote busbar.
When mutual coupling is introduced, the voltage at the relay point A will be
changed according to equation 98.
æ
= × +
Vph Z1 Iph 3 I0
ç
L
è
EQUATION1276 V1 DE
By dividing equation 98
the impedance present to the relay at A side as:
Z0m
Z< Z<
-
Z0
m
-
Z0
m
-
Z0 Z1
L L
× +
3 I0p
×
3 Z1
L
by equation 97 and after some simplification we can write
1MRK 505 186-UDE B
B
en05000221.vsd
Z0 m
C
99000038.vsd
ö
Z0
m
÷
×
3 Z1
ø
L
Applikationshandbuch
(Gleichung 98)