where:
RFPP
Zm
is the setting of the longest reach of the overreaching zones that must be covered by FRPSPDIS
(21).
Equation 277 and 278 are is also valid for three-phase fault. The proposed margin of 25%
will cater for the risk of cut off of the zone measuring characteristic that might occur at
three-phase fault when FRPSPDIS (21)characteristic angle is changed from 60 degrees to
90 degrees or from 70 degrees to 100 degrees (rotated 30° anti-clock wise).
Section 8 1MRK 506 369-UUS -
Impedance protection
344 Line distance protection REL670 2.2 ANSI
Application manual
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