ABB REL650 series Technical Manual page 512

Section 12
Scheme communication
506
• 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 (85).
• 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 236: 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.
0
200ms
AND
50ms
0
1MRK 506 335-UUS A
ECHO - cont.
ECHO
AND
ANSI10000260-1-en.vsd
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