MHI Vestas has chosen Siemens Energy to supply transformers for the turbines to be installed at the 1075MW Seagreen offshore wind project being developed off the coast of Scotland.

Siemens Energy will provide 114 low-loss 66kV fluid immersed distribution transformers designed to facilitate the larger capacities of MHI Vestas’ 10MW turbines while minimising energy losses, the company said.

After commissioning, the distribution transformers will transform the voltage from the low voltage of produced electricity to the medium voltage level of 66kV needed to feed the offshore transmission substation before going to mainland with an even higher voltage.

The transformers have been specifically designed for MHI Vestas’ needs for a lightweight and compact solution that passes through the opening in the tower base without disassembly.

To combine the compactness with challenging and diverging efficiency requirements a newly developed core design, an innovative cooling solution as well as a highly efficient winding arrangement were implemented, Siemens Energy said.

The transformers will be filled with safe and biodegradable ester insulation fluid as an environmentally friendly and operationally safe alternative to conventional mineral oil.

The transformers have been vibration tested to ensure they reliably cope with the highly demanding service conditions and strong vibration typical for wind power applications. In addition, a short circuit test was conducted to ensure the transformers can withstand potential short circuits.

MHI Vestas procurement head Robert Slettenhaar said: “Siemens Energy worked closely together with us to develop a customised design transformer that perfectly fits our demands for an energy efficient solution with minimum footprint.

“The transformers represent a critical component in our wind turbines and I am glad that with Siemens Energy we found a reliable and experienced partner for this significant project.”

About 10,000 fluid immersed transformer units have been built for wind farms in Siemens Energy’s transformer factory in Weiz, Austria, in the last 10 years.

Seagreen is due to begin operations 2022/2023.