ABB RET670 Applications Manual page 275

1MRK504116-UUS C
Application manual
• The possibility of different setting values that influence the ground-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
In this type of networks, the parallel transmission lines terminate at common nodes at
both ends. We consider the three most common operation modes:
1. parallel line in service.
2. parallel line out of service and grounded in both ends.
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.
Let us analyze what happens when a fault occurs on the parallel line see figure 117.
A
Y
ANSI11000087 V1 EN
Figure 117: Class 1, parallel line in service.
The equivalent circuit of the lines can be simplified, see figure 118.
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Section 3
IED application
B
Y
ANSI11000087_1_en.vsd
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