Over current relay

[newt]

How is it possible to have a time over current / instantanous relay for a self contained 15 kv breaker trip only once for instantanous and then trip on time overcurrent? The breaker is 50 years old and the relay is an iac50/51. The reclosing timer is also located in the breaker and we block the instantanous part of this relay for down stream fuse coordination. I don't know why we block the instantanous if we are able to shut it off after it trips once. I was told this was possible.

 

[zog]

Not following you, how can the INST portion of the relay trip your breaker if it is blocked?

 

[newt]

I want to unblock the inst. if there is a way to limit it to one trip and the rest go threw the time delay. So the down stream fuses will blow on time delay,and the inst. unblock will limit arc flash hazard for the lineman.

 

[zog]

Not with an IAC, you would need to replace it with something more modern you can program for something like that.

 

[newt]

Thanks I know we are able to do this with reclosures but wasnt sure about self contained breakers

 

[rcwilson]

Check the Basler website for IAC plug in replacement relays. They package digital or solidstate analog relays that slide into the IAC can. They might have a model that could do this logic.

The digital relay will need power for the logic operation and your breaker may not have DC power available.