Figure 275: Operation logic of instantaneous high stage
Reset of the blocking signals (de-block)
All three blocking signals, that is, waveform and second and fifth harmonic, have a
counter, which holds the blocking on for a certain time after the blocking conditions
have ceased to be fulfilled. The deblocking takes place when those counters have
elapsed. This is a normal case of deblocking.
The blocking signals can be reset immediately if a very high differential current is
measured or if the phase difference of the compared currents (the angle between
the compared currents) is close to zero after the automatic vector group matching
has been made (in a normal situation, the phase difference is 180 degrees). This
does not, however, reset the counters holding the blockings, so the blocking signals
may return when these conditions are not valid anymore.
External blocking functionality
TR2PTDF has three inputs for blocking.
• When the BLOCK input is active ("TRUE"), the operation of the function is blocked
but measurement output signals are still updated.
• When the BLK_OPR_LS input is active ("TRUE"), TR2PTDF operates normally
except that the OPR_LS output is not active or activated in any circumstance.
Additionally, the OPERATE output can be activated only by the instantaneous
high stage (if not blocked as well).
• When the BLK_OPR_HS input is active ("TRUE"), TR2PTDF operates normally
except that the OPR_HS output is not active or activated in any circumstance.
Additionally, the OPERATE output can be activated only by the biased low stage
(if not blocked as well).
4.3.2.5 Application
TR2PTDF is a unit protection function serving as the main protection for
transformers in case of winding failure. The protective zone of a differential
protection includes the transformer, the bus-work or the cables between
the current transformer and the power transformer. When bushing current
transformers are used for the differential protection relay, the protective zone does
not include the bus work or cables between the circuit breaker and the power
transformer.
Protection functions
1MRS757644 H
532 620 series
Technical Manual
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