Relay Instantaneous Element 1

[jps1]

Hi All,
I just want to clearup an issue I have being pondering for a little while.
Lets say you have a relay with the Instantaneous set at, say, 12000A for a CB rated at 1600A. Is it a situation where the Inst. picks up 12KA or higher, or is it at some value below 12KA?


Thanks

 

[dpc]

If the instantaneous element is set for 12,000 A, it will pickup at 12,000 A, plus or minus the slight tolerance in the relay.

If you are talking about medium-voltage or high-voltage circuit breakers, the relay has no idea what the rating of the breaker is.

Generally, there will be a time overcurrent element in addition to the instantaneous.

David Castor

http://www.cvoes.com

 

[JG2828]

The circuit breaker has a 1600A continuous rating, but the interrupting rating may be something like 50,000A.
The time delay relay pickup is most likely set at 1600A or below, depending on what the breaker is feeding.