R
N
Earth return path resistance = (R0 - R1)/3 from measuring point to fault location
X
N
Earth return path reactance = (X0 - X1)/3 from measuring point to fault location
R
0
Zero-sequence resistance from measuring point to fault location
X
0
Zero-sequence reactance from measuring point to fault location
R
F
Physical fault resistance between phase and earth (includes arc and earthing resis-
tances)
Considering the load in case of a single line-to-earth fault, conventional distance
protection might overreach at the exporting end and underreach at the importing
end. DSTPDIS has a load compensation functionality which increases the security in
such applications. Load compensation is enabled with the setting
Load Comp zone
x
(x = 1...5) = "True".
Load compensation is used only with single phase-to-earth faults. Load
compensation is not used if multiple phases are included in the fault
(more than one single earth fault release).
X
R
Load export (No load compensation)
Load import (No load compensation)
Load compensation in use
Figure 538: 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
Protection functions
1MRS759142 F
966 REX640
Technical Manual
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