7.13.6
Monitored data
Table 155:
CCRPLD (52PD) Monitored data
Name
Type
Values (Range)
Unit
Description
IMin
REAL
-
A
Lowest phase current
IMax
REAL
-
A
Highest phase current
7.13.7
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
.
ANSI_en05000287.vsd
poleDiscrepancy Signal from C.B.
+
C.B.
52b
52b
52b
52a
52a
52a
ANSI05000287 V1 EN
Figure 128:
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 506 335-UUS A
Section 7
Current protection
273
Technical manual
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