ABB REL670 2.2 IEC, Applications Manual

Page: 724 / 908

16.4.2 Application
SEMOD156558-1 v1
SEMOD156537-5 v4
Current reversal logic
If parallel lines are connected to common buses at both terminals, overreaching
permissive communication schemes can trip unselectable due to current reversal.
The unwanted tripping affects the healthy line when a fault is cleared on the other
line. This lack of security results in a total loss of interconnection between the two
buses.
To avoid this kind of disturbances, fault current reversal logic (transient blocking
logic) can be used.
The unwanted operations that might occur can be explained by looking into Figure
372 and Figure 373 . Assume that the fault has been taken place close to breaker
B1. At first, the protection A2 at A side will detect a fault in forward direction and
send a communication signal to the protection B2 at remote end, which is
measuring a fault in reverse direction.
L1
L2
A1
A2
B1
B2
IEC14000002-1-en.vsd
IEC14000002 V1 EN-US
Figure 372: Current distribution for a fault close to B side when all breakers are
closed
When the breaker B1 opens for clearing the fault, the fault current through B2 bay
will invert. If the communication signal has not reset at the same time as the
distance protection function used in the teleprotection scheme has switched on to
forward direction, we will have an unwanted operation of breaker B2 at B side.
L1
L2
A1
A2
B1
B2
IEC14000003-1-en.vsd
IEC14000003 V1 EN-US
Figure 373: Current distribution for a fault close to B side when breaker B1 is
opened
To handle this, the send signal CS or CSLx from B2 is held back until the reverse
zone IRVLx has reset and the
tDelayRev time has elapsed. To achieve this, the
reverse zone on the distance protection shall be connected to input IRVLx and the
output IRVOPLx shall be connected to input BLKCS on the communication
function block ZCPSCH.
Section 16
1MRK 506 369-UEN B
Scheme communication
718 Line distance protection REL670 2.2 IEC
Application manual