ABB Relion 670 Series Applications Manual page 395

1MRK 511 358-UUS A
Strong
source
ANSI99000043 V1 EN-US
Figure 187: 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.
Strong
source
ANSI99000044 V1 EN-US
Figure 188: 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
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.
14.2.2.2 Weak-end infeed logic
Permissive communication schemes can basically operate only when the protection in the remote
IED can detect the fault. The detection requires a sufficient minimum fault current, normally >20%
of . 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 requires
a detection of the fault by an independent tripping zone 1. To avoid sequential tripping as
described, and when zone 1 is not available, weak-end infeed tripping logic is used. The weak end
infeed function only works together with permissive overreach communication schemes as the
carrier send signal must cover the hole line length.
The WEI function sends back (echoes) the received signal under the condition that no fault has
been detected on the weak-end by different fault detection elements (distance protection in
forward and reverse direction).
The WEI function can be extended to trip also the breaker in the weak side. The trip is achieved
when one or more phase voltages are low during an echo function.
Application manual
CLOSED
LINE 1
A:1
A
CLOSED
LINE 2
A:2
CLOSED
LINE 1
A:1
A
CLOSED
LINE 2
A:2
tDelayRev time has been elapsed. To achieve this the reverse zone on the distance
CLOSED
FAULT
Weak
source
B:1
B
CLOSED
B:2
en99000043_ansi.vsd
FAULT OPEN
Weak
source
B:1
B
CLOSED
B:2
en99000044_ansi.vsd
Section 14
Scheme communication
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