ABB Relion 650 Series Technical Manual page 361

1MRK 506 326-UUS B
BLOCK
CR
PLTR_CRD
BLKCS
Overreach
CSOR
CSUR
ANSI05000280 V1 EN-US
11.4.6.3 Unblocking scheme
In unblocking scheme, the lower dependability in permissive scheme is overcome by using the loss
of guard signal from the communication equipment to locally create a receive signal. It is common
or suitable to use the function when older, less reliable, power line carrier (PLC) communication is
used.
The unblocking function uses a guard signal CR_GUARD, which must always be present, even when
no CR signal is received. The absence of the CR_GUARD signal for a time longer than the setting
tSecurity time is used as a CR signal, see figure 191. This also enables a permissive scheme to
operate when the line fault blocks the signal transmission.
The received signal created by the unblocking function is reset 150 ms after the security timer has
elapsed. When that occurs an output signal LCG is activated for signaling purpose. The unblocking
function is reset 200 ms after that the guard signal is present again.
CR
CR_GUARD
ANSI05000746 V1 EN-US
Figure 191: Guard signal logic with unblocking scheme
Line distance protection REL650
Technical manual
AND
AND AND
AND
AND
AND
50ms
OR
0
0-tSecurity
NOT
0
200 ms
OR
AND
0
© Copyright 2011 ABB Power Grids. All rights reserved
0
25ms
0-tCoord
0
0
50ms
en05000280_3_ansi.vsd
OR
150 ms
AND
0
Section 11
Scheme communication
CRL
TRIP
CS
OR
CRL
LCG
en05000746_ansi.vsd
M13922-45 v5
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