All four ENERCON E-115 wind energy converters each deliver a rated output of 3 MW and are designed for non-coastal locations with low-wind conditions. The turbines were erected on precast concrete towers with a hub height of 149 metres and have a rotor diameter of 115 metres. The generated electric power is fed into the local power grid using a tower-integrated transformer station. For this purpose, transformer specialists J. Schneider Elektrotechnik located in the city of Offenburg have integrated oil-insulated transformers with an output of 3,500 kVA in the tower bases. The transformer’s function is to convert the low voltage generated by the turbine into the usual medium voltage of 20 kV.
A characteristic challenge when installing transformers in wind turbines is making use of the very limited available space. This is especially the case when efficient cooling of insulating oil utilized to dissipate the loss of power in the form of heat is required. Because the service life of this crucial part was paramount to the Offenburg transformer specialists, they resorted to a KTR solution: the OAC oil and air cooler. Its compact design requires little installation space and above all, enables optimum use of the available ambient height. This paves the way for the integration of the entire feed-in technology into the tower, without having to build any additional buildings.