A transformer arrangement includes a transformer having a winding and a surge arrester arrangement connected thereto. The SAA includes a surge arrester (SA) connected across at least a section of the winding and a switch operable between a closed and open state. In the closed state, SA is electrically connected across at least the section, and in the open state, the SA electrically disconnected from at least the section. The SAA includes at least one further SA .sub.arranged to be connected across at least one further section and at least one further switch, operable between a closed and open state, wherein in the closed state the further SA is electrically connected across the at least one further section, and in the open state, the at least one further SA is electrically disconnected from the further section. A method for electrically connecting/disconnecting the transformer to/from the SAA—is also described.

In aspects, the present invention provides a method for controlled energizing of a transformer (150) being connected to a first electrical subsystem (110) through a first circuit breaker (140). The method comprises acquiring electrical current waveform in a first phase of the transformer during a closing operation of the first circuit breaker at an instance for switching determined by a controller (130), determining a first peak (310) in the current in the first phase within a first predetermined time window (Tpw), calculating a first correction factor for adjusting the instance for switching in the first phase, and adjusting the instance for switching based on the calculated first correction factor for performing a next controlled energization at the adjusted instance of switching in the first phase.

The present disclosure relates to a protective relay detecting disconnection in a circuit comprising a disconnection detection unit including a plurality of nodes connected to both ends of an output of a transformation unit, a reference voltage generation unit forming a reference voltage, and a plurality of resistors forming a voltage dividing resistor and connecting the plurality of nodes and the reference voltage generation unit; a sensing voltage generation unit applying a voltage for forming a predetermined voltage difference with respect to the reference voltage; and a disconnection determination unit connected to a first node, in which the magnitude of a voltage signal applied by the voltage dividing resistor varies depending on whether at least one of the transformation unit and the circuit connected to the transformation unit is disconnected, and detecting whether at least one of the transformation unit and the circuit connected to the transformation unit is disconnected.

Provided is a detecting device and a method for detecting a fault in a transformer of a wind turbine, wherein the transformer transforms a lower voltage, which is output from a generator of the wind turbine to a low voltage side of the transformer, to a higher voltage, which is output from the transformer at a high voltage side, the detecting device including: a voltage detection device configured to detect a voltage at a first node at the low voltage side of the transformer; a current detection device configured to detect a current at a second node at the high voltage side of the transformer. The detecting device is configured to detect the fault in the transformer based on the detected voltage and the detected current.

Provided is a detecting device and a method for detecting a fault in a transformer of a wind turbine, wherein the transformer transforms a lower voltage, which is output from a generator of the wind turbine to a low voltage side of the transformer, to a higher voltage, which is output from the transformer at a high voltage side, the detecting device including: a voltage detection device configured to detect a voltage at a first node at the low voltage side of the transformer; a current detection device configured to detect a current at a second node at the high voltage side of the transformer. The detecting device is configured to detect the fault in the transformer based on the detected voltage and the detected current.

An arrangement for an overvoltage protection of a subsea electrical apparatus and a method for operating it. The arrangement includes a tank submersible below a water surface level, an electrical apparatus accommodated in the tank, and a surge arrester arrangement accommodated in the tank and coupled to a power supply of the electrical apparatus in the tank for providing the overvoltage protection of the electrical apparatus. The arrangement further includes a controllable grounding switch for connecting the surge arrester arrangement to a ground point in response to a control of the grounding switch to a closed state and for disconnecting the surge arrester arrangement from the ground point in response to a control of the grounding switch to an open state.

A device for cancellation of parasitic voltage on the neutral line and for adjusting phase-to-neutral voltage at the remote end of a long power line comprises an autotransformer and at least two single-port-to-multi-port controllable selectors and a controller. The controller is adapted to enable educated selection of taps of the autotransformer by the controllable single-port-to-multi-port controllable selectors, for setting the phase-to-neutral output voltage to nominal voltage and for canceling the parasitic neutral-to-ground voltage.

A device for cancellation of parasitic voltage on the neutral line and for adjusting phase-to-neutral voltage at the remote end of a long power line comprises an autotransformer and at least two single-port-to-multi-port controllable selectors and a controller. The controller is adapted to enable educated selection of taps of the autotransformer by the controllable single-port-to-multi-port controllable selectors, for setting the phase-to-neutral output voltage to nominal voltage and for canceling the parasitic neutral-to-ground voltage.

An over-voltage protection system is provided for use with electrical equipment. The system includes a protection circuit having a first bus for receiving electrical power, a second bus for providing power to the equipment and two parallel surge arresters connected between the first bus and ground. A main and backup bushing are arranged in parallel between the first and second bus. The main bushing is arranged in series with a normally closed contact maintaining the main bushing in service by default. The backup bushing is arranged in series with a normally open contact isolating the backup bushing by default. The protection circuit comprises a controller for testing the insulation of the arresters and bushings. The controller is configured to selectively actuate the contacts to selectively isolate, or incorporate, the arresters and bushings in the circuit to facilitate testing and maintenance while maintaining the protection circuit operational.

The present disclosure relates to a protective relay detecting disconnection in a circuit comprising a disconnection detection unit including a plurality of nodes connected to both ends of an output of a transformation unit, a reference voltage generation unit forming a reference voltage, and a plurality of resistors forming a voltage dividing resistor and connecting the plurality of nodes and the reference voltage generation unit; a sensing voltage generation unit applying a voltage for forming a predetermined voltage difference with respect to the reference voltage; and a disconnection determination unit connected to a first node, in which the magnitude of a voltage signal applied by the voltage dividing resistor varies depending on whether at least one of the transformation unit and the circuit connected to the transformation unit is disconnected, and detecting whether at least one of the transformation unit and the circuit connected to the transformation unit is disconnected.