The performance ability of wind power generators is generally on the rise. That is why the operating voltage of the connection cables from the wind turbines to the collection and connecting platforms is now being increased to 66 kilovolts everywhere. The design of these cables corresponds more to a high-voltage than a medium-voltage cable, which is why the experts at the International Electrotechnical Commission (IEC) decided to permit – in addition to the SOAK test (a 24-hour test at nominal voltage) – only resonance testing for operating voltages greater than 36 kilovolts in the new standard IEC 63026.