A differential protection method for generating a fault signal includes measuring current measurements at least at two different measuring points of a multiphase transformer for each phase. The current measurements for each phase are used to form differential current values and stabilization values. The fault signal is generated if it is determined during a trigger region check that a measurement pair of at least one of the phases, being formed by using one of the differential current values and the associated stabilization value in each case, is in a predefined trigger region. In order to be able to selectively and reliably distinguish an external fault from an internal fault, the transformer has a grounded star point and a zero system current flowing through the star point is used to form the stabilization values. A corresponding differential protection device is provided for performing the differential protection method.

Provided are a system and a method for controlling a frequency. The system for controlling the frequency includes: at least one power supplying unit generating power; at least one systematic unit consuming the power generated from the power supplying unit; at least one standby power unit storing the power generated from the power supplying unit and including at least one storage device; and at least one grid unit connecting the power supplying unit, the systematic unit, and the standby power unit to one another and controlling a frequency of the systematic unit.

Provided are a system and a method for controlling a frequency. The system for controlling the frequency includes: at least one power supplying unit generating power; at least one systematic unit consuming the power generated from the power supplying unit; at least one standby power unit storing the power generated from the power supplying unit and including at least one storage device; and at least one grid unit connecting the power supplying unit, the systematic unit, and the standby power unit to one another and controlling a frequency of the systematic unit.

The present invention relates to a method for operating a wind power facility in order to provide reactive power support to a power grid, the method comprising the step of increasing an amount of reactive power injected into the power grid, decreasing an amount of active power injected into the power grid by a certain amount, and dissipating and/or storing essentially said certain amount of active power in power dissipation and/or power storage means. The wind power facility may comprise a wind turbine or a wind power plant.

A protection system for an electrical variable speed doubly fed induction machine having a stator and a rotor, comprising: instrument transformers capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz; a protection relay which is configured to receive measurement values from the instrument transformers and to sample said measurements values at a constant sampling rate.

A protection system for an electrical variable speed doubly fed induction machine having a stator and a rotor, comprising: instrument transformers capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz; a protection relay which is configured to receive measurement values from the instrument transformers and to sample said measurements values at a constant sampling rate.

Various embodiments include determining an alternating current (AC) voltage and frequency of a supply voltage coupled to a circuit input. The circuit includes a soft starter circuit that is coupled between the circuit input and a first side of an AC motor. A stator winding configuration of the AC motor is determined. A control transformer is configured in response to the AC voltage and frequency, wherein the control transformer is coupled to the circuit input. A jumper device is configured on a second side of the AC motor in response to the stator winding configuration of the AC motor.

Described is a method including monitoring a point of regulation voltage input to a generator control unit and monitoring a generator output voltage as a backup point of regulation voltage input. The method also includes detecting an overvoltage fault at the point of regulation voltage input, the backup point of regulation voltage input, or both. Additionally, the method includes opening a first solid-state switch (110) in response to detecting the overvoltage fault. Opening the first solid-state switch (110) prevents provision of an input signal (104) to a generator excitation field (102). Further, the method includes opening a generator excitation field relay (112) in response to detecting the overvoltage fault. Opening the excitation field relay (112) also prevents provision of the input signal (104) to the generator excitation field (102).

Described is a method including monitoring a point of regulation voltage input to a generator control unit and monitoring a generator output voltage as a backup point of regulation voltage input. The method also includes detecting an overvoltage fault at the point of regulation voltage input, the backup point of regulation voltage input, or both. Additionally, the method includes opening a first solid-state switch (110) in response to detecting the overvoltage fault. Opening the first solid-state switch (110) prevents provision of an input signal (104) to a generator excitation field (102). Further, the method includes opening a generator excitation field relay (112) in response to detecting the overvoltage fault. Opening the excitation field relay (112) also prevents provision of the input signal (104) to the generator excitation field (102).

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.