ABB RET670 Applications Manual page 202

Section 3
IED application
196
Parallel line applications
This type of networks are defined as those networks where the parallel transmission
lines terminate at common nodes at both ends. We consider the three most common
operation modes:
• parallel line in service
• parallel line out of service and grounded
• 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.
Here is the description of what happens when a fault occurs on the parallel line, as
shown in figure 64.
From symmetrical components, it is possible to derive the impedance Z at the IED
point for normal lines without mutual coupling according to equation 104.
V
ph
Z =
-
Z Z
0
+ ×
I 3I
ph 0
×
3 Z
EQUATION1275 V2 EN
Where:
Vph is phase-to-ground voltage at the IED point
Iph is phase current in the faulty phase
3I0 is ground-fault current
Z1 is positive sequence impedance
Z0 is zero sequence impedance
V
ph
=
+ ×
I 3I K
1 ph 0 N
1
1MRK504116-UUS C
(Equation 104)
Application manual