Ungrouded Wye Capacitor Bank Protection

[sykimk]

We are going to purchase the PF correction capacitor banks 13.8kV, 4800kVAR) with ungrounded wye configuration (single wye) with unbalanced voltage protection, and the system grounding is low impedance grounding (400A).

MY client have a concern that capacitive charging currents (circulating current) would be resulting in misoperation of ground OC relay.

I belive it would not be a problem since GF relay setting of 10% of 400A (40A), and the capacitive charging current on system would be ignorable.

Would anybody advise on the GF protection on ungrounded wye capacitor bank?

Thanks in advance.

 

[sykimk]

In addition to this, do you think circulating currents could be a problem with this arrangement?

Thanks in advance for any advices.

 

[burnt2x]

You don't ground the wye point of the PF correction capacitors. If you do, this becomes a parallel path for ground currents during line to gorund faults! The GF protection may miss the fault.

respectfully

 

[dpc]

You ground them if it's a grounded bank. It can be done either way.

http://www.cooperpower.com/library/pdf/KilovarBriefIssue21.pdf

 

[RRaghunath]

sykimk,

The Star point is not grounded when you don't want to burden the capacitors with hamonic load.

The neutral displacement protection works but needs to be time delayed sufficiently to prevent operation during earth faults elsewhere in the system.