ABB Relion 670 Series Technical Reference Manual page 810

Section 13
Scheme communication
13.3.1
13.3.2
13.3.2.1
804
Introduction
The current reversal function is used to prevent unwanted operations due to current
reversal when using permissive overreach protection schemes in application with
parallel lines when the overreach from the two ends overlap on the parallel line.
The weak-end infeed logic is used in cases where the apparent power behind the
protection can be too low to activate the distance protection function. When activated,
received carrier signal together with local undervoltage criteria and no reverse zone
operation gives an instantaneous trip. The received signal is also echoed back during
200 ms to accelerate the sending end.
Three phase or phase segregated scheme logic is available.
Principle of operation
Current reversal logic
The current reversal logic uses a reverse zone connected to the input IREV to
recognize the fault on the parallel line in any of the phases. When the reverse zone has
been activated for a certain settable time tPickUpRev it prevents sending of a
communication signal and activation of trip signal for a predefined time tDelayRev.
This makes it possible for the receive signal to reset before the trip signal is activated
due to the current reversal by the forward directed zone, see figure 395.
IREV
0
0-tPickUpRev
IFWD
ANSI05000122 V2 EN
Figure 395: Current reversal logic
The preventing of sending the send signal CS and activating of the TRIP in the scheme
communication block ZCPSCH (85) is carried out by connecting the IRVL signal to
input BLOCK in the ZCPSCH (85) function.
The function has an internal 10 ms drop-off timer which secure that the current reversal
logic will be activated for short input signals even if the pick-up timer is set to zero.
0 0-tPickUpRev
0
10ms
AND
1MRK505222-UUS C
IRVL
0
0-tDelayRev
ANSI05000122-2-en.vsd
Technical reference manual