This ‘German’ approach faces another challenge. Because wind turbines generate their electricity in AC, large convertor platforms at sea are required whenever HVDC cables are used. Projects usingonly AC cables avoid this expense. Costly and giant AC-DC sea converters are therefore a distinctive featureof German offshore wind parks. Unsurprisingly, these have suffered problems, with Borwin Alpha 1 sustaining lengthy outages whichhas attracted negative publicity. Moreover, a trend towards higher voltages (over 500 kV) for future trading cables, may even require significantly larger and costlier converter installations at sea if they are to be connected with offshore wind-farms