A system for operating an electric machine comprising: - an operation control unit, - an alternating current cable connecting the machine with the operation control unit and that is more than 10 kilometers long, - a local AC bus, - an electric short-circuiting arrangement connected to terminals (38, 40, 42) of the operation control unit facing the cable and to said local AC bus, said arrangement being configured to short circuit said terminals based on an overvoltage detected at said terminals (38, 40, 42), - a step up transformer connected between the operation control unit and the cable, where the operation control unit is connected to the step up transformer via the local AC bus, and - a step down transformer connected between the cable and the electric machine, wherein the operation control unit, the local AC bus, the step up transformer and the short-circuit arrangement are provided in a land installation and the step down transformer and electric machine are provided in a sea installation, - wherein the short-circuiting arrangement comprises a diode bridge connected to said terminals of the operation control unit, a switch which is a thyristor connected for short-circuiting the diode bridge and a short-circuiting control unit for actuating the switch, wherein the switch has a gate and is configured to be closed based on a voltage on the gate, wherein the short-circuiting control unit has two input terminals connected to the two ends of the bridge legs, one connected to one side of the bridge legs and the other connected to the opposite side, wherein the short-circuiting control unit has a control signal output, which provides the control signal that actuates the switch based on the detected DC voltage across the diode bridge legs and which control signal output is connected to the gate of the thyristor. - an operation control unit, - an alternating current cable connecting the machine with the operation control unit and that is more than 10 kilometers long, - a local AC bus, - an electric short-circuiting arrangement connected to terminals (38, 40, 42) of the operation control unit facing the cable and to said local AC bus, said arrangement being configured to short circuit said terminals based on an overvoltage detected at said terminals (38, 40, 42), - a step up transformer connected between the operation control unit and the cable, where the operation control unit is connected to the step up transformer via the local AC bus, and - a step down transformer connected between the cable and the electric machine, wherein the operation control unit, the local AC bus, the step up transformer and the short-circuit arrangement are provided in a land installation and the step down transformer and electric machine are provided in a sea installation, - wherein the short-circuiting arrangement comprises a diode bridge connected to said terminals of the operation control unit, a switch which is a thyristor connected for short-circuiting the diode bridge and a short-circuiting control unit for actuating the switch, wherein the switch has a gate and is configured to be closed based on a voltage on the gate, wherein the short-circuiting control unit has two input terminals connected to the two ends of the bridge legs, one connected to one side of the bridge legs and the other connected to the opposite side, wherein the short-circuiting control unit has a control signal output, which provides the control signal that actuates the switch based on the detected DC voltage across the diode bridge legs and which control signal output is connected to the gate of the thyristor.