ABB RELION REX640 Technical Manual page 113

Protection and control

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1MRS759142 F

Figure 34: Motor feeder fail-safe trip circuit principle, example 4

In example 4, the fail-safe approach aims at securing motor shutdown via an

emergency switch and in case the control voltage disappears. The adjacent panels

provide backup for each other in internal relay fault situations. In case of an internal

relay fault, the situation is noticed by the relay in the adjacent panel and the circuit

breaker in the panel with the faulty relay is tripped after a preset time delay. The

additional time delay allows the relay to recover from the internal fault situation

without tripping the circuit breaker.

Other critical feeders

The examples given for motor feeders can be applied for other types of feeders as

well. The following examples are for critical feeders in which the protection system

dependability, security or both are the drivers.

Technical Manual

Feeder #1 panel

Feeder #2 panel

Emergency stop

Circuit breaker

Relay trip output #1

Relay trip output #2

Relay internal fault indication

Relay binary input #1

CB undervoltage trip coil

CB trip coil 1

Miniature circuit breaker

Basic functions