ph ph
0 1 ph N
ph 0
1
0
V V
Z Z I 3 K
I 3I
3 Z
I
Z = =
- + ×
+ ×
×
EQUATION1275 V3 EN-US (Equation 27)
Where:
Vph is phase-to-earth voltage at the IED point
Iph is phase current in the faulty phase
3I0 is earth-fault current
Z1 is positive sequence impedance
Z0 is zero sequence impedance
Z0m
A B
Z< Z<
en05000221.vsd
IEC05000221 V1 EN-US
Figure 59: Class 1, parallel line in service
The equivalent circuit of the lines can be simplified, as shown in figure 60.
A
B
C
Z0
m
Z0
Z0
m
-
Z0
Z0
m
-
99000038.vsd
IEC99000038 V1 EN-US
Figure 60: 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 IED point A is changed,
according to equation 28.
Section 8 1MRK 506 369-UEN B
Impedance protection
154 Line distance protection REL670 2.2 IEC
Application manual
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