Unblocking Scheme - ABB REL650 series Technical Manual

1MRK 506 335-UUS A
12.5.6.3
Technical manual
measurement element will be used as sending criterion of the permissive input signal
CSUR.
In the overreaching alternative, an overreaching directional residual overcurrent
measurement element will be used as sending criterion of the permissive input signal
CSOR. Also the underreaching input signal CSUR can initiate sending.
BLOCK
CR
PLTR_CRD
BLKCS
Overreach
AND
CSOR
CSUR
ANSI05000280 V1 EN

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 247. 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.
AND
0-tCoord
AND AND
AND
AND
50ms
OR
0
Section 12
Scheme communication
0
25ms
0
0
50ms
OR
en05000280_3_ansi.vsd
CRL
TRIP
CS
521