Relay

A lock-out relay is a relay that locks out the circuit breaker in OFF Condition after a fault trip. The main protective relay, normally is in Self Reset Mode and after a fault trip and after the current subsides to a level below the set current, the protective relay would reset automatically. The operating person, who may not be aware of this fault trip, might attempt another close of the CB. Supposing the fault is stil persisting, this - reclosing on to a fault - would be the most onerous duty that the CB would perform and might live out its life. To prevent this eventuality, a lock-out relay is used, which is energised by the fault relay. But, this lock out relay is always Manual Reset. So, after a CB trip on fault, a person has to go near the CB, analyse the cause for the CB trip and take a decision whether to re-close the CB or not. The ANSI Code for this relay is '86'.

A lockout relay is nominally a relay that is part of an interlock system. Depending on how and why the system gets locked out, a different level of relay reliability will be required. For simple tasks that will have no consequence to humans or machines, any suitable relay could be used. The lockout relay of an arcade video game can fail in any mode and have little consequences. The lockout relay circuit for a heavy machine press must only fail in a way that disables the press to maintain a safe operation.

Lockout relay (ANSI device 86) is the master trip relay. It is used in the protection control circuit in such a fashion that it is operated (powered) if any fault condition occurs. Once it is operated, it is latched and can be reset only with manual intervention but it can not be reset until the fault is cleared. A contact of the lockout relay is used to trip the breaker. This relay ensures not to close the beaker if fault condition sustains.

See the previous posting:

http://cr4.globalspec.com/thread/33601

- MS