IEC08000437 V1 EN
Figure 60: Rotation of load characteristic for a fault between two phases
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 one.
6.2.6.5 Minimum operate currents
The operation of the Phase selection with load encroachment function (FDPSPDIS, 21) is
blocked if the magnitude of input currents falls below certain threshold values.
The phase-to-ground loop n is blocked if In<IMinPUPG, where In is the RMS value of the
current in phase n (A or B or C).
The phase-to-phase loop mn is blocked if (2·In<IMinPUPP).
1MRK 506 335-UUS A Section 6
Impedance protection
141
Technical manual
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