3
U
0
U
L
1
U
L
2
U
L
3
U
L
2
F
U
L
3
F
U
L
3
F
en06000551.vsd
IEC06000551 V1 EN-US
Figure 246: Voltage distribution before and during a single phase-to-earth fault
During a cross-country fault, the fault current path for the fault that is not on the
protected feeder will not go through the relay. (For a more meshed network though,
there will be some current.) See Figure
247. Only in the one phase with the fault on
the protected feeder, a significant fault current may be measured by the relay. The
result is a residual current of the same magnitude. This residual current may be
used as an indication of a cross-country fault.
IL3=IN
IL1=IN
en06000553.vsd
IEC06000553 V1 EN-US
Figure 247: The currents in the phases at a double earth fault
1MRK 506 369-UEN B Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 451
Application manual
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