corner grounded delta

[Ektar]

We have a deep well pump application were a 480V soft-start feeds a step up 480-2400 delta delta transformer, which in turn supplies a 200hp pump.

Should the 2400V delta secondary be corner grounded or ungrounded?

(the 2400V conductors are run underground, in concrete encased conduit, and then down into the well)

Thanks

 

[busbar]

The 2400V circuit should be high-resistance grounded with about 1 ampere of resistive fault current. It is unfortunate that a wye 2400V winding was not specified—that would have allowed for a simplified application of a resistor from H0-to-ground for this purpose. This scheme will limit damage under fault conditions, but damp any transient or resonant overvoltage on the 2400V circuit. Simple non-tripping ground detection could be accomplished by monitoring current through or voltage across the grounding resistor.

Because of the simplicity of the arrangement, surge protection at 2400V is probably unnecessary.