Design of Sudden Pressure Relay Blocking Scheme for Transformer

[jhonsom]

How to design SPR blocking scheme using 63 and 50 Fast instantaneous over current element?
Is SPR used for tripping the relay for internal faults only?

How will it block tripping if 63 contacts are short because of transient?

The logic I'm having in my mind is= 63A And not 63B not 87 not 50) will trip the relay , is my thinking correct?

 

[dpc]

Sudden pressure relay is used for detection of internal transformer faults. But they are sometimes prone to mis-operation during transients. Blocking schemes can be used to block operation during through faults. I've heard of these schemes, but never seen one used.

If you have an energize-to-trip scheme, you'll need a normally closed contact in series with the 63 tripping contact ("a" contact) that will open during whatever conditions you want to block.

The differential 87 trip contact should not be blocked.

David Castor

http://www.cvoes.com

 

[cranky108]

As was pointed out to me by another engineer, 63 relays can pickup during sysimic events, and should be blocked to prevent misoperation. However your point about transits is valid.