ABB RELION REX640 - Checking CT circuits; Checking VT circuits

TO Protection relay trip output
IRF Internal relay fault indication
<U CB undervoltage trip coil
TC1 CB trip coil 1
DCS Distributed process control system
F1 Miniature circuit breaker
In example 2, the fail-safe approach aims at securing motor shutdown via an
emergency switch and in case the control voltage disappears. In case of internal
relay fault, the necessary actions must be initiated by the process operators or by
the control system.
<U
TC1
-Q0
AUX. POWER
-A1
-F1
Control +
Control -
ES
IRF
-K1
-K1
TO
Figure 33: Motor feeder fail-safe trip circuit principle, example 3
A1 Protection relay
ES Emergency stop
Q0 Circuit breaker (CB)
TO Protection relay trip output
IRF Internal relay fault indication
<U CB undervoltage trip coil
TC1 CB trip coil 1
K1 OFF delay time relay
F1 Miniature circuit breaker
In example 3, the fail-safe approach aims at securing motor shutdown via an
emergency switch and in case the control voltage disappears. In case of internal
relay fault, the circuit breaker is tripped via an undervoltage coil after a preset time
delay. The additional time delay allows the relay to recover from the internal fault
situation without tripping the circuit breaker.
Basic functions
1MRS759142 F
112 REX640
Technical Manual