Wind Turbine Interconnection - Transformer Configuration

[Dumbo2929]

Does anyone have experience designing wind turbine interconnections? My experience with generator step-up transformers is to have a delta-wye, with the delta on the generator side, and a wye on the utility side. One of the leading turbine manufacturers is proposing a wye-wye transformer connection, or even a wye-delta, with the wye on the generator side and a delta on the utility side.
This project is relatively small, with to 1.5MW turbines, each with a 2000kVA from 575V on the turbine side to 13.8kV utility voltage. Any thoughts??

 

[waross]

I prefer the wye delta with the delta next to the generation for better distribution of unbalanced loads. I work a lot with a small utility which has chronically unbalanced loads.
respectfully

 

[davidbeach]

Any time you have a generator - transformer combination the ideal winding on the generator side of the transformer is a delta. Not as critical with low voltage generators as with higher voltage machines, but that delta winding facilitates much better protection of the generator. High side could be either wye or delta but is usually grounded-wye to provide a ground reference for the line.

 

[dpc]

If the 13.8 kV side is connecting directly to a utility distribution feeder and assuming the wind machine is an induction generator, I'd probably be inclined toward a wye-delta, with the delta on the utility side. This provides some isolation from their zero sequence current and gives you somewhere to ground the 575 V side, if you care to do that. With a grounded wye on the utility side and a delta on the generator side, you will have a essentially a grounding transformer that will source ground fault current on the 13.8 kV even if the generator is off-line, this may require a 13.8 kV circuit breaker along with requisite relaying.

If you can come up with a connection that both the utility and the wind turbine supplier agree on, consider yourself lucky.

 

[ters]

I’m presently working on wind projects and prevailing unit transformer connection appears to be Y on the low (generator) side and delta on the collection line side. If an intermediate transformer is involved (if the collection line voltage is not the same as utility line voltage) typically another Y on the low side Delta on the high step up transformer is implemented.

However, unit transformer configuration may be influenced by the type of wind machine - many older ones are asynchronous generators, while newer ones are increasingly synchronous generators (sometimes with 6 phases) and with the AC/DC/AC converter between the generator and transformer, allowing so generation at variable rotor speed and eliminating a need to have a gear box (speed increaser).

As for the intermediate transformers, their connection may be imposed by the utility you connect to and their practices.