Grounded Neutral on Load Bank TX Question

[tumbleweed1]

We have a 4160V to 600V Delta (primary) Wye (secondary) transformer, 1.5MVA.

I had planned to simply ground the neutral on the secondary wye side as the load bank does not require line-neutral load. I understand that this poses a risk for excessive ground fault current to flow.

We have a zero sequence CT on the feeder. Would this mitigate the risk/minimize the time that a ground fault could occur?

 

[cranky108]

Load Bank? Or is this a load?

If there is no line to neutral load there is the option to use an impedance to reduce the fault current for a phase to ground fault. And since a phase to ground fault is the most common, it would reduce chances of a big fault.

A CT on the feeder does not reduce anything. It simply makes it easer to detect a fault.

If you keep your feeder cables in different ducts, conduits, etc. It makes it unlikely you can have anything other than a ground fault, and combined with a neutural impedance can make the ground fault very small.

 

[mls1]

If you stick with solid grounding then there's no reason to use zero sequence CTs, just use the residual connection of the phase CTs or ground setting on the trip units. Zero sequence CTs are only necessary for low level ground fault currents in resistance or impedance grounded systems.

I would consider that if you don't have any phase to neutral loads then use an HRG. It will still allow ground detection but with reduced damage from ground faults. In that case you will need a zero sequence CT or a CT in the neutral connection (often provided with the HRG system).

 

[tumbleweed1]

Thanks mls1, that clarifies some things there. Guess I was really wondering if there's any way to detect a ground fault on a solidly grounded system with my present setup.