en05000278.vsd
TRIPRESL1
TRIPRESL2
TRIPRESL3
OR
TRIPRES
TRIPUNREL1
TRIPUNREL2
TRIPUNREL3
OR
TRIPUNRE
OR
TRIP
TRNSUNR
TRNSSENS
IEC05000278 V1 EN
Figure 41: Transformer differential protection internal grouping of tripping
signals
IEC05000279-TIFF V1 EN
Figure 42: Transformer differential protection internal grouping of logical signals
Logic in figures 39, 40, 41 and 42 can be summarized as follows:
1. The three fundamental frequency differential currents are applied in a phase
segregated manner to two limits. The first limit is the operate-restrain
characteristic, while the other is the high-set unrestrained limit. If the first limit is
exceeded, a start signal START is set. If the unrestrained limit is exceeded, an
immediate unrestrained trip TRIPUNRE and common trip TRIP are issued.
2. If a start signal is issued in a phase the harmonic and the waveform block signals
are checked. Only a start signal, which is free of all of its blocking signals can
result in a trip command. If the cross-block logic scheme is applied, then only if
Section 6 1MRK 504 135-UEN A
Differential protection
108
Technical manual
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