Doubt About Zigzag Earthing Transformers at Site

I didn't knew that zigzag transformers had a neutral! Is it a new improvement~?

I think I made a mistake over there, I didn't mean an actual neutral I meant the point where the 3 phase of the secondary side of the transformer are jointly connected to earth..

I think that is a electrical "mass" what you are refering... or the secondary is in star configuration.

This link shows a picture of how the zigzag earthing transformer is connected:

http://i52.tinypic.com/122m9fq.jpg

You can imagine how it will become if the earth point at the secondary side is removed..

I don't know about how safe, but wouldn't have thought it the most efficient way of doing it.

I am sure your right, but unfortunately that's the way it is connected.. The zigzag transformers were only added 3 years ago because in the future we will demolish the generator..

By Principles, you are right.

1. But, We hope for the best, with DG sets, creation of unbalanced voltages is a rare case, as Generator's neutral is always earthed. So, un balanced high voltages on the zig zag transformers will be the very very rare case. Transformer will remain safe during normal operations.

2. But, definitely, Generators will not be prtected by relays connected to zog zag transformers. It will always be for mains breaker only.

I see your point, our generator has its own high resistance earthing and its protection. The zig zag transformer will only be used as a earth reference when the generator is disconnected from the busbar. So I guess as long as unbalanced condition does not exist, the zig zag transformer will remain safe.

What about any harmonics or zero sequence currents flowing in the grid will it be a major concern to the zigzag transformer in this case?

Yes, it is safe that way. Earth faults will only be supplied from the generator whose neutral is earthed (there will not be zero sequence currents in the zigzag transformer).

Thank you for your clarification..