7 APPLICATION NOTES
7.1 AIDED DISTANCE PUR SCHEME
This scheme allows an instantaneous Zone 2 trip on receipt of the signal from the underreaching element of the
remote end protection.
The logic is:
● Send logic: Zone 1
● Permissive Trip logic: Zone 2 plus channel received
The time delay setting (Aid.1 Dist. Dly, Aid.2 Dist. Dly) should be set to 0 ms for fast fault clearance.
7.2
AIDED DISTANCE POR SCHEME
This scheme allows This scheme allows an instantaneous Zone 2 trip on receipt of the signal from the
overreaching element of the remote end protection.
The logic is
● Send logic: Zone 2
● Permissive Trip logic: Zone 2 plus channel received
The time delay setting (Aid.1 Dist. Dly, Aid.2 Dist. Dly) should be set to 0 ms for fast fault clearance.
The POR scheme also uses the reverse looking zone 4 IED as a reverse fault detector. This is used in the current
reversal logic and in the optional weak infeed echo feature.
Weak Infeed
Where weak infeed tripping is employed, a typical voltage setting is 70% of rated phase-neutral voltage. Weak
infeed tripping is time delayed according to the WI Trip Delay value, usually set at 60ms.
Current Reversal Guard
The recommended setting is:
● tReversal Guard = Maximum signalling channel reset time + 60 ms.
7.3
AIDED DISTANCE BLOCKING SCHEME
This scheme uses a reverse looking zone 4 element to block operation of a forward looking zone 2 element at the
remote end protection.
The logic is:
● Send logic: Reverse Zone 4
● Trip logic: Zone 2, plus Channel NOT Received
To allow time for a blocking signal to arrive, a short time delay must be allowed before tripping (Aid.1 Dist. Dly, Aid.
2 Dist. Dly). The recommended delay is as follows:
● Recommended setting = Maximum signalling channel operating time + one power frequency cycle.
Note:
Two variants of a Blocking scheme are provided, Blocking 1 and Blocking 2. Both schemes operate similarly, except that the
reversal guard timer location in the logic changes. Blocking 2 may sometimes allow faster unblocking when a fault evolves
from external to internal, and hence a faster trip.
P543i/P545i Chapter 8 - Carrier Aided Schemes
P54x1i-TM-EN-1 245
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