1. parallel line in service.
2. parallel line out of service and grounded.
3. parallel line out of service and not grounded.
Parallel line in service
This type of application is very common and applies to all normal sub-transmission and
transmission networks.
A simplified single line diagram is shown in figure
139.
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 (Equation 195)
Where:
Vph is phase-to-ground voltage at the IED point
Iph is phase current in the faulty phase
3I0 is ground to fault current
Z1 is positive sequence impedance
Z0 is zero sequence impedance
Z0m
A B
Z< Z<
en05000221.vsd
IEC05000221 V1 EN
Figure 139: Class 1, parallel line in service.
The equivalent circuit of the lines can be simplified, see figure 140.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 287
Application manual
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