Toshiba GRZ100-211B, Instruction Manual

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39
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6 F 2 S 0 8 3 4
VaX: imaginary part of phase “a” voltage
VaR: real part of phase “a” voltage
IaX: imaginary part of phase “a” current
IaR: real part of phase “a” current
I0X: imaginary part of zero-sequence current of the protected line
I0R: real part of zero-sequence current of the protected line
IomX: imaginary part of zero-sequence current of the parallel line
IomR: real part of zero-sequence current of the parallel line
Figure 2.4.1.14 Earth Fault Compensation
The zero-sequence compensation factors are applied to the earth fault measuring elements as
shown in the table below
Element Protected line Parallel line
Z1G Krs, Kxs Krm, Kxm
Z1XG Krs, Kxs Krm, Kxm
Z2G Krs, Kxs Krm, Kxm
Z3G − −
ZFG − −
ZR1G KrsR, KxsR −
ZR2G − −
Z4G
− −
ZNDG − −
−
: Compensation is not provided.
The zero-sequence compensation of the parallel line is controlled by the ZPCC (Zero-sequence
Current Compensation) element.
When an earth fault occurs on the protected line, the ZPCC operates and parallel line
compensation is performed to prevent underreach caused by the mutual zero-sequence current of
the parallel line.
When an earth fault on the parallel line occurs, the ZPCC does not operate and the compensation
of parallel line is not performed to prevent overreach. The operating condition of the ZPCC is as
follows:
3I0 / 3Iom
≥
0.8
Charging current compensation
When distance protection is applied to underground cables or long-distance overhead lines, the
effect of charging current cannot be ignored. It appears as a distance measurement error in the
fault.
I0’
I1, I2, Io
Z1, Z2, Zo
Zom
P
F
Va
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