ABB RET670 Applications Manual page 373

1MRK504116-UUS C
Application manual
distance protection. The second fault can, but does not need to, occur within this
time interval.
• Fault on an adjacent line (behind the B substation, see figure 162) causes the
measured impedance to enter the operate area of ZMRPSB (68) function and, for
example, the zone 2 operating characteristic (see figure 163). Correct fault
clearance initiates an evolving power swing so that the locus of the measured
impedance continues through zone 1 operating characteristic and causes its
unwanted operation, if no preventive measures have been taken, see figure 163.
A
Z
SA
E
A
IEC06000238 V1 EN
Figure 162: Fault on adjacent line and its clearance causes power swinging
between sources A and C
ZMRPSL function and the basic operating principle of ZMRPSB (68) function operate
reliably for different faults on parallel power lines with detected power swings. It is,
however, preferred to keep the distance protection function blocked in cases of single
phase-to-ground faults on so far healthy lines with detected power swings. In these
cases, it is recommended to use an optionally available directional overcurrent ground-
fault protection with scheme communication logic.
B
RA
F
Section 3
IED application
C
Z
SC
E
C
Z
SD
E
D
D
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