A new kind of overvoltage, not covered by present standards, has been detected in solar plants when switching the inverters off. This power frequency overvoltage can be transmitted to the MV network, giving rise to damages to some pieces of low voltage electronic equipment. This phenomenon has been investigated in the field, testing several inverters in different solar plants, where the overvoltages, as well as the damages in revenue meters, have been reproduced and recorded. It has been proved that some inverter configurations are more prone to create severe overvoltages than other. In addition, some solutions have been tested and a laboratory test to reproduce the phenomenon is proposed