Operation Principle - ABB REG650 Technical Manual

Section 7
Current protection
7.5.7
186

Operation principle

Breaker failure protection (CCRBRF) is initiated from protection trip command,
either from protection functions within the IED or from external protection devices.
The start signal is general for all three phases. A re-trip attempt can be made after a
set time delay. The re-trip function can be done with or without current or contact
check. With the current check the re-trip is only performed if the current through
the circuit breaker is larger than the operate current level. With contact check the re-
trip is only performed if breaker is indicated as closed.
The start signal can be an internal or external protection trip signal. This signal will
start the back-up trip timer. If the opening of the breaker is successful this is
detected by the function, both by detection of low RMS current and by a special
adapted algorithm. The special algorithm enables a very fast detection of successful
breaker opening, that is, fast resetting of the current measurement. If the current
detection has not detected breaker opening before the back-up timer has run its
time a back-up trip is initiated.
Further the following possibilities are available:
• In the current detection it is possible to use three different options: 1 out of 3
where it is sufficient to detect failure to open (high current) in one pole, 1 out
of 4 where it is sufficient to detect failure to open (high current) in one pole or
high residual current and 2 out of 4 where at least two current (phase current and/
or residual current) shall be high for breaker failure detection.
• The current detection level for the residual current can be set different from the
setting of phase current detection.
• Back-up trip is always made with current or contact check.It is possible to
have this option activated for small load currents only.
Current
BLOCK
STIL1
START
CBCLD
IEC08000007 V1 EN
Figure 96: Simplified logic scheme of the retrip function
AND
Current &
Contact
AND AND
OR
AND
AND
Contact
1MRK 502 034-UEN -
t1
t
OR
TRRET
OR
L2 L3
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Technical Manual