Transformers for wind turbines are generally hidden away in a green box next to the tower. However, out on the open sea, they tend to be placed in the gondola itself, on the outside of the turbine or even on separate platforms when their role is as a central offshore transformer station for a large wind farm. What most transformers have in common is that they have until now been insulated and cooled using mineral oil. Yet the fact that these insulating fluids are flammable and pose an environmental risk makes it necessary to look for alternatives, especially for use on sensitive sites.