Zig-Zag on Delta Bus

[stretched2thin]

It is my understanding that Line-to-Ground faults can occurr on a Delta bus if you have a zig-zag grounding transformer connected to this bus. Is this correct?

 

[DanDel]

A Zig-Zag grounding transformer provides a consistent potential to ground for each phase. Since there is a potential to ground, a ground fault can occur. Because of the inherent design of the Zig-Zag system, however, the GF current is usually limited because it must flow through two windings of the transformer system.

 

[ohhn]

Normally, when you have a delta distribution system, you usually grounded through a zizg zag transformer.
The transformer provides a path to ground for any ground fault in the system; allowing the ground relay to trip for this fault, otherwise the relays will operate until you have a double fault.
I installed a delta 15 KV distribution system in Cameroon and this was the way they usually did it.
I must confess most of my experience is with so called "american" systems where all the distribution systems are grounded star.

 

[busbar]

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[jbartos]

Suggestion: Visit

http://www.powerohm.com/catalog/NGCAT00.pdf

etc. for more info on zigzag transformer
The grounding zigzag transformers are usually rated for 10Second, 100% insulation level
This needs to have the upstream protector tripped within 10seconds, else the transformer may be permanently damaged.
The non-triplen harmonics will flow through the zigzag to the ground. Now, it depends on how the primary of transformer with delta secondary is system grounded. If there is a wye winding with solidly grounded neutral system grounding, then the zigzag transformer will experience more stable voltage in comparison with the wye connected primary without a solidly grounded neutral system grounding.