Abstract: A method for determining direction of an earth fault (EF) in a feeder of a high impedance grounded power system can be performed by an Intelligent Electronic Device (IED). The method includes obtaining a measure of a first order harmonic active current component derived from residual voltage and current of the feeder when the EF occurred in the feeder, obtaining a measure of a higher order harmonic reactive current component derived from the residual voltage and current of the feeder when the EF occurred in the feeder, and determining the direction of the EF in the feeder based on a combination of the first order harmonic active current component and the higher order harmonic reactive current component.

Abstract: An arrangement for injection-based ground fault protection handling including a number of stator windings of an electric machine that are connected to a neutral point, a first transformer including at least one primary winding connected to at least one measurement point of the stator windings and at least one secondary winding for measuring an electrical quantity of the machine at the measurement point. There is also a second transformer having a primary winding connected between the neutral point and a ground potential and a secondary winding for connection to a signal generation and detection unit in order to inject a signal into the neutral point and receive a response. The impedance of the second transformer is in the range of the impedance of the machine.

Abstract: A method for determining direction of an earth fault (EF) in a feeder of a high impedance grounded power system can be performed by an Intelligent Electronic Device (IED). The method includes obtaining a measure of a first order harmonic active current component derived from residual voltage and current of the feeder when the EF occurred in the feeder, obtaining a measure of a higher order harmonic reactive current component derived from the residual voltage and current of the feeder when the EF occurred in the feeder, and determining the direction of the EF in the feeder based on a combination of the first order harmonic active current component and the higher order harmonic reactive current component.

Abstract: An arrangement for injection-based ground fault protection handling including a number of stator windings of an electric machine that are connected to a neutral point, a first transformer including at least one primary winding connected to at least one measurement point of the stator windings and at least one secondary winding for measuring an electrical quantity of the machine at the measurement point. There is also a second transformer having a primary winding connected between the neutral point and a ground potential and a secondary winding for connection to a signal generation and detection unit in order to inject a signal into the neutral point and receive a response. The impedance of the second transformer is in the range of the impedance of the machine.

Abstract: A monitoring device and a method for detecting mechanical torsional oscillations in a rotor shaft of a turbine-generator system. Specifically, the monitoring device and a method for detecting mechanical torsional oscillations in a turbine-generator system having a plurality of, such as two, three, four, five, six or more, turbines that are interconnected by means of a common turbine shaft.

Abstract: A monitoring device and a method for detecting mechanical torsional oscillations in a rotor shaft of a turbine-generator system. Specifically, the monitoring device and a method for detecting mechanical torsional oscillations in a turbine-generator system having a plurality of, such as two, three, four, five, six or more, turbines that are interconnected by means of a common turbine shaft.

Abstract: A method for detecting an internal failure in a capacitor bank connected in one phase or more phases respectively to a power system. The capacitor bank includes a plurality of capacitor units. Each of the capacitor units includes a plurality of capacitor elements connected in parallel and/or series. The capacitor units are further divided into two strings and a current transformer is arranged in the midpoints of the two strings so that the capacitor units are further divided into four quadrants and the internal failure(s) may occur in one or more capacitor elements or units and involves one or more capacitor quadrants. The method includes initiating an alarm and/or a trip signal when the determined total number of internal elements failures exceeds a first or a second threshold value.

Abstract: A method for detecting an internal failure in a capacitor bank connected to a power system, wherein the capacitor bank includes a plurality of capacitor units that are divided into two Y sections. Each phase in each of the Y sections defines a leg and each leg includes series and/or parallel-connected capacitor units. The internal failure may occur in one or more capacitor elements or units or involve one or more legs. The method includes measuring the phase current in one of the phases, calculating the root mean square value, denoted by RMS, of the measured phase currents, measuring the unbalanced current between the two sections, calculating the RMS value of the measured unbalanced currents, and detecting the phase angle between the measured phase current and the measured unbalanced current.

Abstract: An arrangement to detect a ground fault in an AC electric circuit including an electric machine having a neutral point connecting to a neutral point and a terminal side, and a unit transformer connected to the terminal side of the machine, wherein the arrangement includes a signal injection unit, a voltage transformer having a primary winding connected to the terminal side of the electric machine and a secondary winding that is open delta-connected, an instrument transformer having a primary winding connected to the neutral point of the electric machine and a secondary winding, and a ground fault detecting unit. The signal injection unit is configured to inject a signal to the secondary winding of the voltage transformer. The instrument transformer is configured to measure the resultant injected signal at its secondary winding The ground fault detecting unit is configured to detect a ground fault based on the measured signal.

Abstract: A system, method and computer program product for monitoring including detecting internal faults especially inter-turn faults of a synchronous generator and thus protecting the synchronous generator. The synchronous generator includes a winding for each phase of a power network, a terminal for each phase arranged on a terminal side of the synchronous generator, and connected to the respective winding, the terminals on the terminal side are connected to an electrical power network, and the synchronous generator is arranged to input power to the electrical power network by means of the terminals.

Abstract: A method for protecting against a failure within a multi-phase capacitor bank including a plurality of capacitor units each including a plurality of capacitor elements connected to each other, wherein capacitor units are connected to each other and the failure may involve two neighboring capacitor units. The method includes steps of measuring the current of each individual phase of the capacitor bank, calculating the magnitude of an unbalanced current based on the measured currents, measuring the voltage of each individual phase of the capacitor bank, calculating the magnitude of an unbalanced voltage based on the measured voltages, determining an operating point based on the calculated magnitudes of the unbalanced current and the unbalanced voltage, examining where the defined operating point is located in a specified operating region, and initializing a trip signal based on the location of the defined operating point in the specified operating region.

Abstract: A synchronization method for current differential protection comprises: selecting a point on the transmission line protected by the current differential protection; measuring the current and the voltage of each of the terminals of said transmission line; calculating the compensating voltage at the selected point respectively according to the measured current and the voltage of the each terminal; detecting and calculating the synchronization error by comparing all the compensating voltages.

Abstract: A system, method and computer program product for monitoring including detecting internal faults especially inter-turn faults of a synchronous generator and thus protecting the synchronous generator. The synchronous generator includes a winding for each phase of a power network, a terminal for each phase arranged on a terminal side of the synchronous generator, and connected to the respective winding, the terminals on the terminal side are connected to an electrical power network, and the synchronous generator is arranged to input power to the electrical power network by means of the terminals.

Abstract: A method for detecting an internal failure in a capacitor bank connected in one phase or more phases respectively to a power system. The capacitor bank includes a plurality of capacitor units. Each of the capacitor units includes a plurality of capacitor elements connected in parallel and/or series. The capacitor units are further divided into two strings and a current transformer is arranged in the midpoints of the two strings so that the capacitor units are further divided into four quadrants and the internal failure(s) may occur in one or more capacitor elements or units and involves one or more capacitor quadrants. The method includes initiating an alarm and/or a trip signal when the determined total number of internal elements failures exceeds a first or a second threshold value.

Abstract: A method for detecting an internal failure in a capacitor bank connected to a power system, wherein the capacitor bank includes a plurality of capacitor units that are divided into two Y sections. Each phase in each of the Y sections define a leg and each leg includes series and/or parallel-connected capacitor units. The internal failure may occur in one or more capacitor elements or units or involve one or more legs. The method includes measuring the phase current in one of the phases, calculating the root mean square value, denoted by RMS, of the measured phase currents, measuring the unbalance current between the two sections, calculating the RMS value of the measured unbalance currents, and detecting the phase angle between the measured phase current and the measured unbalance current.

Abstract: An arrangement to detect a ground fault in an AC electric circuit including an electric machine having a neutral point connecting to a neutral point and a terminal side, and a unit transformer connected to the terminal side of the machine, wherein the arrangement includes a signal injection unit, a voltage transformer having a primary winding connected to the terminal side of the electric machine and a secondary winding that is open delta-connected, an instrument transformer having a primary winding connected to the neutral point of the electric machine and a secondary winding, and a ground fault detecting unit. The signal injection unit is configured to inject a signal to the secondary winding of the voltage transformer. The instrument transformer is configured to measure the resultant injected signal at its secondary winding The ground fault detecting unit is configured to detect a ground fault based on the measured signal.

Abstract: A synchronization method for current differential protection comprises: selecting a point on the transmission line protected by the current differential protection; measuring the current and the voltage of each of the terminals of said transmission line; calculating the compensating voltage at the selected point respectively according to the measured current and the voltage of the each terminal; detecting and calculating the synchronization error by comparing all the compensating voltages.

Abstract: A method for protecting against a failure within a multi-phase capacitor bank including a plurality of capacitor units each including a plurality of capacitor elements connected to each other, wherein capacitor units are connected to each other and the failure may involve two neighboring capacitor units. The method includes steps of measuring the current of each individual phase of the capacitor bank, calculating the magnitude of an unbalanced current based on the measured currents, measuring the voltage of each individual phase of the capacitor bank, calculating the magnitude of an unbalanced voltage based on the measured voltages, determining an operating point based on the calculated magnitudes of the unbalanced current and the unbalanced voltage, examining where the defined operating point is located in a specified operating region, and initializing a trip signal based on the location of the defined operating point in the specified operating region.

Abstract: An arrangement for protecting equipment of an AC electrical power system comprises first means configured to measure the frequency of the current and voltage at at least one location in the electrical power system along an interconnection between two theoretical electric machines of an equivalent two machine system. Fourth means are configured to use the values of the frequency of the current and voltage measured to determine whether a power swing has occurred and if an occurrence of a power swing has been determined determine whether the measuring location is located on a motor side or a generator side of a potential pole slip electrical centre along said interconnection, the electrical centre being defined as the location where the voltage becomes zero during a pole slip, and send this information further to third means for use in a control for protecting equipment of the electrical power system.

Abstract: An arrangement for protecting equipment of an AC electrical power system comprises first means configured to measure the frequency of the current and voltage at at least one location in the electrical power system along an interconnection between two theoretical electric machines of an equivalent two machine system. Fourth means are configured to use the values of the frequency of the current and voltage measured to determine whether a power swing has occurred and if an occurrence of a power swing has been determined determine whether the measuring location is located on a motor side or a generator side of a potential pole slip electrical centre along said interconnection, the electrical centre being defined as the location where the voltage becomes zero during a pole slip, and send this information further to third means for use in a control for protecting equipment of the electrical power system.