ABB Relion Technical Manual page 256

Section 8
Current protection
250
C.B.
52a
52a
52a
52b
52b
52b
ANSI05000287 V1 EN
Figure 114: Pole discrepancy external detection logic
This binary signal is connected to a binary input of the IED. The appearance of this signal
will start a timer that will give a trip signal after the set time delay.
Pole discrepancy can also be detected by means of phase selective current measurement.
The sampled analog phase currents are pre-processed in a discrete Fourier filter (DFT)
block. From the fundamental frequency components of each phase current the RMS value
of each phase current is derived. The smallest and the largest phase current are derived. If
the smallest phase current is lower than the setting CurrUnsymPU times the largest phase
current the settable trip timer (tTrip) is started. The tTrip timer gives a trip signal after the
set delay. The TRIP signal is a pulse 150 ms long. The current based pole discrepancy
function can be set to be active either continuously or only directly in connection to
breaker open or close command.
+
poleDiscrepancy Signal from C.B.
1MRK 502 048-UUS A
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