wind farm trf connections 1

[mersin33]

Hello,

I am working on a wind farm project and I would like to hear your comments about system grounding in wind farms.

Different from the typical, generators are 600V Delta, with 0.6/34.5kV step up transformers with grounded wye at the 600V side (requirement of the generator).

The main transformer at the substation is 34.5/115kV with grounded Y at the 115kV side (requirement of the utility).

I would like to learn your thoughts about what the best step up and main transformer configurations should be from economics / system protection point of view.

Thanks in advance for your comments.

 

[dpc]

My first thought would be to make the small collector transformers delta-delta and make the big guy (34.5 - 115 kV) a wye-wye with a delta tertiary.

This would give you a ground reference on the 34.5 kV, as long as it's energized. If it's not energized, there isn't much point in any of the 34.5 kV system being energized anyway.

Other option would be a wye-wye for the little transformers, but that's not a great solution in terms of ground fault protection and coordination and may not provide adequate ground fault current at 34.5 kV.

But there are a lot of these systems already installed, so I'm sure someone else has already worked through this. You might want to hire a consultant with some actual experience.

Advice here is free, but you get what you pay for.

 

[Kiribanda]

mersin33,

I think the transformer connections you have given are seems to be ok which are also typical in Distributed Generator setups (IEEE 1547).It is a must that 115 kV Utility side should be solid grounded.

I also believe that you had already taken care about the 34.5 kV DELTA-DELTA ungrounded portion from ground faults. Is it overhead or underground?

Hope this helps!

 

[vic3fan]

The Wye grounded-Wye grounded transformers, even with the Delta-connected tertiary have a major inconvenient: a grounded fault on the 34.5kV side may be ‘transferred’ on the 115kV side and the protection should be such as to not trip for this type of fault. It can be done, but at the cost of some compromises from the protection point of view.

But, if you have the step-up unit transformer Wye grounded-connected on the 0.6 kV side and the utility asks for Wye grounded on the 115kV side, why not having the 34.5kV collector system Delta-connected? In other words, what’s the problem with a 0.6kV Yg/34.5kV D unit transformer and a 34.5kV D/115kV Yg power step-up transformer? In this case, make sure you provide on the 34.5kV collector system enough grounding transformers zig-zag connected to detect grounding faults.

 

[mersin33]

First of all, thank you very much for your inputs.

Kiribanda: The collector system is partly underground, partly overhead.

vic3fan: Basically this was the option I had in mind.

Regards,