ABB Relion 670 series - Weak-End Infeed Logic

en99000044_ansi.vsd
Strong
source
LINE 1
LINE 2
A:1
A:2
B:1
B:2
A B
Weak
source
CLOSED
CLOSED
OPEN
CLOSED
FAULT
ANSI99000044 V1 EN
Figure 373: 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
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 complete 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).
Also, the WEI function can be extended to trip the breaker in the weak side. The trip is
achieved when one or more phase voltages are low during an echo function.
In case of single-pole tripping, the phase voltages are used as phase selectors together with
the received signal CRLn.
Together with the blocking teleprotection scheme some limitations apply:
1MRK 506 369-UUS - Section 16
Scheme communication
Line distance protection REL670 2.2 ANSI 763
Application manual