IEC08000437 V1 EN
Figure 164: Rotation of load characteristic for a fault between two phases
This rotation may seem a bit awkward, but there is a gain in selectivity by using the same
measurement as for the quadrilateral characteristic since not all phase-to-phase loops will
be fully affected by a fault between two phases. It should also provide better fault resistive
coverage in quadrant 1. The relative loss of fault resistive coverage in quadrant 4 should
not be a problem even for applications on series compensated lines.
8.10.3 Load encroachment characteristics
The phase selector must at least cover the overreaching zone 2 in order to achieve correct
phase selection for utilizing single-phase autoreclosing for faults on the entire line. It is not
necessary to cover all distance protection zones. A safety margin of at least 10% is
recommended. In order to get operation from distance zones, the phase selection output
PHSELZ or PHSELI must be connected to input PHSEL on distance zones.
For normal overhead lines, the angle for the loop impedance φ for phase-to-ground fault
defined according to equation
96.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 339
Application manual
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