IEC08000437 V1 EN-US
Figure 90: 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. The relative loss of fault resistive
coverage in quadrant four should not be a problem even for applications on series compensated
lines.
7.2.6.5 Minimum operate currents
M13140-102 v3
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
).
7.2.6.6 Simplified logic diagrams
M13140-107 v7
Figure 91 presents schematically the general logic diagram for phase-selection function.
1MRK 502 066-UUS B Section 7
Impedance protection
209
Technical manual
To Next Page
Loading...
