ABB REL670 2.2 IEC, Applications Manual

Page: 721 / 908

The unwanted operations that might occur can be explained by looking into
Figure
370 and Figure 371 . Initially 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
IEC9900043-2.vsd
IEC99000043 V3 EN-US
Figure 370: 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
IEC99000044-2.vsd
IEC99000044 V3 EN-US
Figure 371: Current distribution for a fault close to B side when breaker B1 has
opened
To handle this the send signal CS or CSLn from B2 is held back until the reverse
zone IRVLn has reset and the
tDelayRev time has been elapsed. To achieve this the
reverse zone on the distance protection shall be connected to input IRV and the
output IRVL shall be connected to input BLKCS on the communication function
block ZCPSCH.
The function can be blocked by activating the input IRVBLK or the general
BLOCK input.
16.3.2.2 Weak-end infeed logic
M13895-16 v8
Permissive communication schemes can only operate when the protection in the
remote IED can detect the fault. The detection requires a sufficient minimum fault
current, normally >20% of I
r
. The fault current can be too low due to an open
breaker or low short-circuit power of the source. To overcome these conditions,
weak-end infeed (WEI) echo logic is used. The fault current can also be initially
too low due to the fault current distribution. Here, the fault current increases when
the breaker opens at the strong terminal, and a sequential tripping is achieved. This
1MRK 506 369-UEN B
Section 16
Scheme communication
Line distance protection REL670 2.2 IEC 715
Application manual