Weak-End Infeed Logic - ABB REL650 series Technical Manual

1MRK 506 335-UUS A
12.3.6.2
Technical manual

Weak-end infeed logic

The weak-end infeed logic (WEI) function trip and 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 returns the received signal, see figure 236, when:
• No active signal present on the input BLOCK.
• The functional input CRL is active. This input is usually connected to the CRL output
on the scheme communication logic ZCPSCH.
• The WEI function is not blocked by the active signal connected to the WEIBLK1
functional input or to the BLKZ functional input. The later is usually configured to
the BLOCK functional output of the fuse-failure function.
• No active signal has been present for at least 200 ms on the WEIBLK2 functional
input. An OR combination of all fault detection functions (not undervoltage) as
present within the IED is usually used for this purpose.
BLKZ
BLOCK
OR
CRL
-
0 tWEI
0
WEIBLK1
WEIBLK2
0
200ms
ANSI10000260 V1 EN
Figure 240: Echo of a received signal by the WEI function
When an echo function is used in both IEDs (should generally be avoided), a spurious
signal can be looped round by the echo logics. To avoid a continuous lock-up of the
system, the duration of the echoed signal is limited to 200 ms.
An undervoltage criteria is used as an additional tripping criteria, when the tripping of the
local breaker is selected, setting WEI = Echo & Trip, together with the WEI function and
ECHO signal has been issued by the echo logic, see figure 237.
Information from the open circuit breaker can be connected to the input CBOPEN to avoid
WEI-trip if the circuit breaker already was opened.
0
200ms
AND
50ms
0
Section 12
Scheme communication
ECHO - cont.
ECHO
AND
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