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Differential trip 1

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khadisa

Electrical
Joined
Dec 19, 2005
Messages
22
Location
GB
We have a transformer that deliver full load current, but trips on through fault. The relay is Duo-bias (Reyrolle C21)
 
Scotty,

Thanks for your comments - that's along the same lines as feedback I have had from our relay supplier.

The ratio is an exact match (1000/1), CT resistances are both quoted at 75deg C and the FLC of the circuit is around 870A. I will check with the vendor re the magnetising current of the new CT.

The reason for replacing the existing neutral CT (mounted within switchboard) is that it was damaged during modifications being made to the generator incomer cubicle.
 
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