6.9.6 Monitored data
Table 83: CCRPLD (52PD) Monitored data
Name
Type Values (Range) Unit Description
IMin REAL - A Lowest phase current
IMax REAL - A Highest phase current
6.9.7 Operation principle
The detection of pole discrepancy can be made in two different ways. If the contact based
function is used an external logic can be made by connecting the auxiliary contacts of the
circuit breaker so that a pole discrepancy is indicated, see figure 60.
ANSI_en05000287.vsd
poleDiscrepancy Signal from C.B.
+
C.B.
52b
52b
52b
52a
52a
52a
ANSI05000287 V1 EN
Figure 60: 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.
1MRK 511 287-UUS A Section 6
Current protection
147
Technical manual
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