Directional Relay 67 Application

[faresos]

I’m reviewing a project for MV power distribution (12.47KV). The system is configured as Main-Tie-Main; Two power sources from utility (A & B) and the tie is normally open. The system will have an automatic transfer scheme (via relays) upon loss of one of the sources. The MV distribution bus feeding multiple buildings (via transformers), each building will receive two feeders (from bus A & B) for redundancy. I have noticed the engineer have used relays (50/51, 51N, 67 and 32) for the feeders. My understanding the directional relays 67 & 32 are needed at the mains but not sure if they are really needed at the feeders. Any thoughts on why they are needed at the feeders?

Thanks,

 

[Ingenieur]

Could power flow down feeder A and back on feeder B (to bus B)?

 

[faresos]

Could power flow down feeder A and back on feeder B (to bus B)?

The only way happens the way I see it if the loads were motors and the tie breaker is closed when a fault happens on bus B. Since we have an open transition transfer scheme then I would say it's not possible. Do you agree?

 

[rian0201]

maybe it is a feature available, not activated.. or he is thinking tie is not normally open...


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