Innogy has completed the annual maintenance of its 295MW Nordsee Ost offshore wind farm in Germany, including inspection of wind turbine blades and foundations, and maintenance of the offshore substation.The company said it successfully completed its own scope of maintenance work for this year. However, some service providers still have to finish their maintenance work at Nordsee Ost offshore wind farm.This year, innogy used a drone for visual inspection for the first time, with 12 of the 48 wind turbines being examined more closely from the tower, over the nacelle and all the way to the rotor blade tip by rope-access blade inspections.Inspection of the foundations is carried out both above and under water surface, including inspections of the weld and bolt connections, visual inspections of the structures and inspections of the corrosion protection coating. Special subsea robots were used for underwater inspections, which usually take around one to two days per foundation. A total of 50 foundations were inspected above water: all 48 wind turbine foundations, the jacket foundation of the offshore substation and the monopile foundation of the met mast. Of the 50 foundations, 13 were also examined under water.Image: innogyOffshore substation’s primary systems, such as switchgear and transformers, and secondary systems, such as the control and protection technology, were tested this summer with the support of the innogy subsidiary Westnetz. In addition, maintenance has been performed on the fire alarm and the fire extinguishing systems, cranes, air-conditioning and ventilation system, as well as other smaller auxiliary systems.During the summer, when the wind farm is in full swing, the annual maintenance campaigns are due to take place. “Summer is the best time of the year for us,” said Tobias Matzke, Production Manager at innogy. “With the beginning of autumn, weather windows in which maintenance is possible decrease. Our experience shows that from October, statistically speaking, the accessibility to the wind turbines and our substation at sea is halved compared to summer. We are therefore glad that we were able to successfully complete our annual maintenance before the first autumn storms. “Approximately 50 service technicians, engineers and nautical staff are working on the German offshore wind farm to ensure its safe and economic operation, innogy said.