However, if the SeriesComp option is chosen (only available in ZMFCPDIS) the value
is changed to 0.95.
7.4.7.5 Fuse failure
The ZMFCPDIS function has to be blocked by an additional function like the Fuse
failure supervision (FUFSPVC) or an equivalent external device. Typically, the
binary input VTSZ is used for this purpose.
However, to guarantee that also very fast operation is blocked in a fuse failure
situation, there is a built-in supervision based on change in current that will delay
operation before the FUFSPVC blocking signal is received. The delay will be
introduced if no (vector) magnitude change greater than 5% of IBase has been
detected in any of the phase currents.
7.4.7.6 Power swings
There is need for external blocking of the ZMFCPDIS function during power swings,
either from the Power Swing Blocking function (ZMRPSB) or an external device.
7.4.7.7 Measuring principles
All ZMFCPDIS zones operate according to the non-directional impedance
characteristics presented in figure 95 and figure 96. The phase-to-earth characteristic
is illustrated with the full loop reach while the phase-to-phase characteristic presents
the per-phase reach.
1MRK502052-UEN B Section 7
Impedance protection
241
Technical manual
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