Well, We have decided we would rely on the 52a contact for isolation of the trip coil. The wide voltage range is because the breaker operates on 250Vdc and it is not permitted to have 250V dc at the main control room.
This trip coil is a dedicated one to trip the breaker under accident...
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...
