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The following is applicable to LV systems - not sure whether it also applies to 3.3kV but I don't see why not... Fuse-contactor arrangement is ok provided that the fuses and contactor are selected to co-ordinate with each other (type 2 co-ordination - IEC 60947-4-1). Check whether the...

Are the pump-sets located in a hazardous area? If so is it zone 1 or zone 2? This would have to be considered if changing the motors from fixed to variable speed. As a minimum for variable speed motors in hazardous areas, motor thermistors would need to be connected in order to directly trip...

In my experience, different clients aproach this issue differently with regard to their willingness to rely on programmable logic of intelligent relays. It's quite common for ESD and emergency stop push-button trips to be hardwired into the control scheme (so that they are not reliant on any...

Regarding the harmonic resonance, by adding a large lump of capacitance to the system, I'd have thought you are likely to change the overall system resonance point - to what extent would depend on size of sytem/amount of capacitance being added. Need to be careful here as if you have any...

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...

Can anyone comment on the requirement for matching of Class X CT's? We are having to replace the Class X neutral CT in an LV generator REF protection scheme. I have nameplate details of the original CT, but the CT that has been offered by my supplier has slightly different characteristics -...