EQUATION2115 V1 EN (Equation 271)
But in some applications, for instance cable lines, the angle of the loop might be less than
the set angle. In these applications, the settings of fault resistance coverage in forward and
reverse 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 the phase
selection characteristic must 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.
The following setting guideline considers normal overhead lines applications and
provides two different setting alternatives:
A) A recommended characteristic angle of 60 degrees
for the phase selection
B) A characteristic angle of 90 and 70 degrees for
phase-to-ground and phase-to-phase respectively,
like implemented in the REL500 series
The following figures illustrate alternative B).
8.10.3.1 Phase-to-ground fault in forward direction
With reference to figure 165, 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 (FRPSPDIS, 21) and index Zm
reference settings for Distance protection function (ZMRPDIS).
Section 8 1MRK 506 369-UUS -
Impedance protection
340 Line distance protection REL670 2.2 ANSI
Application manual
To Next Page
Loading...
