direction, RFltFwdPG and RFltRevPG for phase-to-ground faults and RFltRevPP and
RFltRevPP for phase-to-phase faults have to be increased to avoid that FDPSPDIS (21)
characteristic shall cut off some part of the zone characteristic. The necessary increased
setting of the fault resistance coverage can be derived from trigonometric evaluation of the
basic characteristic for respectively fault type.
Phase-to-ground fault in forward direction
With reference to figure 106, the following equations for the setting calculations can be
obtained.
Index PHS in images and equations reference settings for Phase selection
with load encroachment function FDPSPDIS (21) and index Zm reference
settings for Distance protection function (ZMQPDIS, 21).
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 217
Application manual
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