Circuit Breakers and Autoreclosing 1

[Jorgy1]

Does the duty cycle of a circuit breaker have anything to do with autoreclosing? We have a CB with duty cycle of CO-15s-CO. We are to implement an autoreclosing scheme consisting of one fast reclosing of 0.5sec and one delayed reclosing of 15sec. I have been wondering whether the CB is suitable. It is a SF6 spring charged CB for an 11KV distribution line.

George.

 

[RalphChristie]

Yes, it does.
But are there not a part missing on your quote?

CO - 15s - CO

For a one shot it would look something like this:
O - 0.3s - CO
open on fault, wait 0.3 seconds, close once on fault, open (and lock-out)
For two shots it would look something like this:
O - 0.3sec - CO - 15 sec - CO
Open on a fault, wait 0.3 seconds, close again on the fault, open, wait 15 seconds, close for the second time on the fault, open.(and lock-out)

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[jghrist]

The ANSI standards have changed. The standard duty cycle used to be CO-15s-CO. The latest standard is O-0.3s-CO-15s-CO. If the breaker was manufactured under the new standard, then your O-0.5s-CO-15s-CO duty cycle is OK. You'd better check with the manufacturer.

 

[cuky2000]

Circuit breakers rated for duty cycle [red]t= 0.3 s (300 ms)[/red] intended for rapid auto-reclosing (dead time). The description provided appears not sufficient to determine if the MV circuit breaker is suitable for fast (rapid) reclosing.

Probably the best source will be the breaker manufacturer.
Enclose is generic information mostly from IEEE Std C37.

I hope this help.

 

[jghrist]

See

http://webapp.ptd.siemens.com/tech_topics/TechTopics29Rev0.pdf

for a discussion of derating factors for reclosing service.