In this case the logic is realized within the function. If the inputs are indicating pole
discrepancy the trip timer is started. This timer will give a trip signal after the set 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.
The function also has a binary input that can be configured from the autoreclosing
function, so that the pole discrepancy function can be blocked during sequences with a
single pole open if single pole autoreclosing is used.
en 05000747_ansi.vsd
OR
BLOCK
BLKDBYAR
52b_A
52a_A
52b_B
52a_B
52b_C
52a_C
Pole
Disc repancy
detection
PolPosAuxCont
AND
PD signal from CB
AND
EXTPDIND
Unsymmetry current
detection
OR
CLOSECMD
OPENCMD
t+ 200 ms
AND
OR
AND
TRIP
0 - t
0
150 ms
ANSI05000747 V1 EN
Figure 236: Simplified block diagram of pole discrepancy function CCRPLD (52PD)
- contact and current based
CCRPLD (52PD) is disabled if:
• The IED is in TEST mode and CCRPLD (52PD) has been blocked from the local
HMI
• The input signal BLOCK is high
• The input signal BLKDBYAR is high
1MRK505222-UUS C Section 7
Current protection
467
Technical reference manual
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