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1MRK 506 369-UEN B
Line distance protection REL670 2.2 IEC
Application manual
•
Parallel line with common positive and zero sequence network
•
Parallel circuits with common positive but isolated zero-sequence network
•
Parallel circuits with positive and zero sequence sources isolated
One example of class3 networks could be the mutual coupling between a 400 kV
line and rail road overhead lines. This type of mutual coupling is not so common
although it exists and is not treated any further in this manual.
For each type of network class we can have three different topologies; the parallel
line can be in service, out of service, out of service and earthed in both ends.
The reach of the distance protection zone1 will be different depending on the
operation condition of the parallel line. It is therefore recommended to use the
different setting groups to handle the cases when the parallel line is in operation
and out of service and earthed at both ends.
The distance protection within the IED can compensate for the influence of a zero-
sequence mutual coupling on the measurement at single phase-to-earth faults in the
following ways, by using:
•
The possibility of different setting values that influence the earth-return
compensation for different distance zones within the same group of setting
parameters.
•
Different groups of setting parameters for different operating conditions of a
protected multi circuit line.
Most multi circuit lines have two parallel operating circuits. The application guide
mentioned below recommends in more detail the setting practice for this particular
type of line. The basic principles also apply to other multi circuit lines.
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 earthed
•
parallel line out of service and not earthed
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 59.
From symmetrical components, it is possible to derive the impedance Z at the IED
point for normal lines without mutual coupling according to equation 27.
Section 8
Impedance protection
SEMOD168232-169 v2
SEMOD168232-176 v3
153
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