HV intertrip
HV intertrip
(OP)
If you have an HV breaker 11kV feeding a 11kV/400VAC transformer, and no breaker on the output from the LV side, the cables go directly to the switchboard, I have normally seen an inter trip to the LV breaker if the HV trips out. I have recommended this to a customer but cant think exactly why you need it, I assume to isolate the tx completely?






RE: HV intertrip
RE: HV intertrip
RE: HV intertrip
Regards
Marmite
RE: HV intertrip
RE: HV intertrip
Regards
Matrixabc
RE: HV intertrip
RE: HV intertrip
Usually find the tranny input to the first ACB has restricted earth fault REF. This protects the trany secondary and bus to the first oc protection. If a tranny winding goes to earth you may find severe damage to the tranny before the incomer picks it up and trips.
This REF relay provides a back trip signal to trip both the ACB and the HV breaker isolating the transformer.
You mentioned generator back feed - you would need to have some form of interlocking between the tranny and generator to prevent this from happening. If your HV goes down and the genny back feeds the tranny and then the HV is restored then you would have a pretty significant bang.
simple switching schedule HV breaker trips signal trips the LV breaker. LV incommer trips this does not need to back trip the HV - Id be careful with this.
Also bear in mind that some tranys dont like being connected to the HV with a load connected - Inrush can develop some serious spikes on the LV side - hence its best to have the LV open when making up your HV.
Less to worry about.
Rugged