Ungrounded Delta Zigzag Grounding

[wiigelec]

We have an ungrounded delta system (480V). We are considering installing a zigzag grounding transformer to create an artificial neutral.

Does this artificial neutral and corresponding ground provide an effective ground fault path (zero-sequence) that will allow downstream residual or BYZ ground fault protective devices to function?

Thanks...

 

[beanland]

Zigzag

Zigzag

Yes, that is the purpose of the zigzag, provide zero-sequence current for ground fault relays to detect. The rating and impedance of the zigzag and whether there is a resistor added to the neutral all determine how much ground fault current it contributes. There are specific definitions in IEEE about what "effective grounding" means so the addition of a zigzag may not provide effective grounding per IEEE. Strongly suggest working with a grounding transformer supplier and/or engineer because this is a poorly understood area.