Interposing relay.
Interposing relay.
(OP)
We are in the process of introducing a time delay relay to prevent continuous energisation of the trip coil of a 13.8kv breaker under specific circumstnces. The relay coil would have to act under 48v dc but the contact would be a 250vdc one. We would need aninterposing relay. I need to be clear in all factors needed to choose this relay. Any suggestions would be appreciated.





RE: Interposing relay.
Otherwise, consider General Electric Type HGA, or if you need a lot of contacts, you could use a General Electric Type HFA.
RE: Interposing relay.
The reason for the wide DC-voltage range spec is not apparent, but in most cases an auxiliary "52a contact" [and possibly anti-pump feature] are furnished on the original assembly to interrupt trip-coil power when the breaker mechanically opens. Such controls must be carefully evaluated as highly reliable for some fierce inductive-DC interruption characteristics.
Be cautious of trip-control modifications that are outside of those OEM furnished. It is very likely the OEM has been through a lengthy learning curve, and it can be most preferable learning from them—as opposed to experiencing a metal-vaporizing maloperation first hand.
RE: Interposing relay.
This trip coil is a dedicated one to trip the breaker under accident conditions and we should avoid the breaker from charging again. We are thinking about providing contacts to seal in the motor to avoid charging of a closing spring after a trip. These contacts have to be of a high rating, I realize that this is an issue to be handled with caution I need expert advice on choosing such a Relay or is there any other option.
RE: Interposing relay.
Examples of these relays would be GE type HEA, Electroswitch type LOR, Alstom type MVAJ - check their websites for details.
The breaker 52a contact is still required in the trip circuit, as it is for any application. This contact is rated to break the high DC current in the trip coil.
RE: Interposing relay.
It is known that the trip coil of CB is always isolated by breker auxiliary contact.