ABB RELION REX640 Technical Manual page 893

1MRS759142 C
REX640
Technical Manual
X
GUID-5D30395A-5108-40AE-B055-1B4E82A3BA3D V1 EN
Figure 479: Operation principle of load compensation functionality
When three-phase feeders are placed close to each other, a mutual inductive zero-
sequence coupling of the current path exists. This has an impact during earth faults. If
no measures are taken, this leads to errors in the impedance calculation. The residual
current of the parallel line induces a voltage in the protection line and changes the
measured voltage at the relay location. The influence depends on the system
configuration, that is, the magnitude and polarity of the residual current in a parallel
line.
The phase-to-earth impedance measuring elements in DSTPDIS take the zero-
sequence mutual coupling into account in impedance calculation. The compensation
is enabled and set with settings Par line Comp zone x (="True"), Mutual R0 zone x and
Mutual X0 zone x (x = 1...5). The residual current of the parallel line must be available
and connected to the I3P_PAR input. The earth-current balance logic is implemented
to prevent malfunctioning of the protection relay on the healthy parallel line. This
means that the parallel compensation functionality is internally blocked when the ratio
between residual current of the parallel line and protected lines exceeds the Fact EF
current Bal configuration setting.
The parallel line compensation functionality is only used with single
phase-to-earth faults. Parallel line compensation is not used if
multiple phases are included into fault (more than one single earth
fault releases).
Protection functions
Load import (No load compensation)
Load compensation in use
Load export (No load compensation)
R
Section 4
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