MV/LV Transformer output
MV/LV Transformer output
(OP)
I have a configuration with 3 MV/LV transformers: 2 working and 1 standby with an auto-transfer scheme(I attached a single line diagram)
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- In normal operation, buscouplers 1 and 2 are open
- Standby transformer can feed either busbar 1 or 2 (interlocks)
i.e When the standby transformer is working it feeds only one side, through buscoupler (CB).
- Distance between transformers and busbar : ~ 20m
- applicable code: IEC
I'm asking if in this case if an additionnal CB at the standby transformer output is necessary or not?
Please advise.
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- In normal operation, buscouplers 1 and 2 are open
- Standby transformer can feed either busbar 1 or 2 (interlocks)
i.e When the standby transformer is working it feeds only one side, through buscoupler (CB).
- Distance between transformers and busbar : ~ 20m
- applicable code: IEC
I'm asking if in this case if an additionnal CB at the standby transformer output is necessary or not?
Please advise.






RE: MV/LV Transformer output
Case 1: Stand by transformer is feeding the left side via Buscoupler 1. In case there is a bus fault, tripping of buscoupler 1 breaker (and the incoming side breaker) will isolate the transformer. Same is the case with stand by transformer feeding the right side via buscoupler 2 breaker. In this case, tripping of buscoupler 2 breaker will isolate the transformer from the fault.
Case 2: In case there is a transformer fault, then tripping of buscoupler breakers 1/2 will isolate the fault from the healthy bus.
Bus-coupler breakers itself act as standby transformer breaker.
RE: MV/LV Transformer output
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If we learn from our mistakes I'm getting a great education!
RE: MV/LV Transformer output
RE: MV/LV Transformer output
ScottyUK : there is no load on the centre bus section
jghrist : breakers motor operated