Abstract: In the field of power system stability there is provided a method of predicting the presence of an out-of-step condition in a power system that includes a plurality of generators, the method including the steps of: (a) obtaining a differential value ({tilde over (?)}COIk) between a rotor angle (?k) of an individual one of the plurality of generators and an equivalent rotor angle (?COIk) of the centre of inertia of the remainder of the plurality of generators; (b) processing the differential value ({tilde over (?)}COIk) to determine whether the differential value ({tilde over (?)}COIk) is predicted to reach a predefined reference threshold (?threshold); and (c) predicting the presence of the out-of-step condition in the power system if the differential value ({tilde over (?)}COIk) is predicted to reach the predefined reference threshold (?threshold).

Abstract: The technology described herein is generally directed to a method of locating a fault in a multi-terminal electrical power transmission scheme, such as implemented in a power transmission scheme where each of six terminals is connected with one of four junctions via a power transmission section and each junction interconnects a plurality of power transmission sections. Aspects of the described technology can be directed to measuring the voltage and current at each terminal, calculating from the measured voltage and current at each terminal corresponding voltage and current phasors, determining from the calculated voltage and current phasors a synchronization difference between the measured voltage and current at a designated terminal and the measured voltage and current at each other terminal, modifying the calculated voltage and current phasors to compensate for each synchronization difference, and determining from the compensated voltage and current phasors the location of the fault.

Abstract: Systems and methods of determining a communication time delay in electrical power systems are provided. In one embodiment, a method of determining a communication time delay in a communication network between a local terminal and each of a plurality of remote terminals in a multi-terminal multi-junction electrical power system includes: (a) calculating a respective initial communication time delay between each remote terminal and the local terminal; (b) calculating a respective junction time delay between respective first, second and third pairs of adjacent junctions; and (c) correcting the calculated initial communication time delay of each remote terminal spaced from the local terminal by two or more junctions according to each corresponding junction time delay arising between the or each remote terminal and the local terminal.

Abstract: An apparatus for determining a fault location distance or distance protection in a multi-phase power transmission medium, configured to; determine a set of line fault parameters based on a measurement of voltage and current at a point of said power transmission medium and a fault type, the line fault parameters determined at a plurality of sample times determine a derivative with respect to time of a line fault parameters representative of an inductive part of measured faulty phase current; determine a set of phasors using a Fourier transformation of the derivative and of the remaining line fault parameters at the plurality of sample times and use said set of phasors to determine a fault location distance or distance projection distance along the power transmission medium; wherein, the determination of the fault location distance or the distance protection distance is based on the line equation; U . P = U . F + [ R 1 ? I . PR + X 1 ? 0 ? I . PX ] ? D F .

Abstract: A circuit interruption apparatus, for an electrical network, comprising a circuit interruption device that is operatively connectable at a source side to a source of the electrical network and at a back side to a load of an electrical network. The circuit interruption device when closed permits and when open inhibits the current flow between the source side the back side. The current interruption device is configured to open when a current flowing therethrough meets or exceeds a fault current threshold. The circuit interruption apparatus also includes a fault current level determination unit that is configured to determine a predicted fault current level as a function of measured current and voltage values at the circuit interruption device before and after a variation in the current and voltage values at the circuit interruption device that result from a change of load at the back side of the circuit interruption device.

Abstract: A DC distance protection scheme for protecting a DC power transmission medium within the DC electrical power network. The DC distance protection scheme includes a protection device that is coupled in use to a DC power transmission medium. The protection device is operable to protect the DC power transmission medium from an electrical fault. The DC distance protection scheme also includes a measurement apparatus to selectively measure the current and voltage of the DC power transmission medium. In addition the DC distance protection scheme also includes a controller that is programmed to calculate an operating voltage of the DC power transmission medium using the measured current and voltage; perform a transient comparison between the calculated operating voltage and the measured voltage; and operate the protection device to protect the DC power transmission medium if the transient comparison meets a predefined criterion.

Abstract: A DC protection scheme for protecting a DC power transmission medium within a DC electrical power network. The scheme includes a protection device coupled to a DC power transmission medium, being operable to protect the power transmission medium from a fault; an apparatus to measure at least one electrical property of the power transmission medium; and a controller programmed to determine the direction of the electrical fault; determine whether the electrical fault is an internal or external fault; and operate the protection device to protect the DC power transmission medium if the determination of the direction of the electrical fault and/or the determination of whether the electrical fault is an internal or external fault meet a predefined criterion.

Abstract: In differential protection schemes for electrical power systems there is a need to employ a synchronization technique to enable time alignment of local terminal current with received current from a remote terminal in order reliably to operate the differential protection scheme. A method of determining a communication time delay in a communication network between a local terminal and each of a plurality of remote terminals in a multi-terminal multi junction electrical power system includes: (a) calculating a respective initial communication time delay between each remote terminal and the local terminal; (b) calculating a respective junction time delay between respective first, second and third pairs of adjacent junctions; and (c) correcting the calculated initial communication time delay of each remote terminal spaced from the local terminal by two or more junctions according to each corresponding junction time delay arising between the or each said remote terminal and the local terminal.

Abstract: An apparatus for determining a measure of the frequency of an electrical signal is provided. The apparatus is configured to, based on a plurality of samples of the electrical signal, determine a Hilbert transformation to obtain a value for each of the samples of the electrical signal for use as an imaginary representation of each of the samples of the electrical signal and combine each said imaginary representation with a corresponding real representation of the samples of the electrical signal to form a complex representation of the electrical signal; perform a Fourier transform on each said complex representation of the samples of the electrical signal and determine a phase angle therefrom; and determine a measure of the frequency of the electrical signal based on a derivative of the phase angle with respect to time.

Abstract: Embodiments of the disclosure relate to systems and methods of locating a fault in a multi-terminal power transmission scheme. According to at least embodiment of the disclosure there is provided a method of locating a fault in a multi-terminal electrical power transmission scheme in which each terminal is connected with a junction via a power transmission section and the or each junction interconnects a plurality of power transmission sections.

Abstract: In the field of power system stability there is provided a method of predicting the presence of an out-of-step condition in a power system that includes a plurality of generators, the method including the steps of: (a) obtaining a differential value (?COIk) between a rotor angle (?k) of an individual one of the plurality of generators and an equivalent rotor angle (?COIk) of the centre of inertia of the remainder of the plurality of generators; (b) processing the differential value (?COIk) to determine whether the differential value (?COIk) is predicted to reach a predefined reference threshold (?threshold); and (c) predicting the presence of the out-of-step condition in the power system if the differential value (?COIk) is predicted to reach the predefined reference threshold (?threshold).

Abstract: A DC protection scheme for protecting a DC power transmission medium within a DC electrical power network. The scheme includes a protection device coupled to a DC power transmission medium, being operable to protect the power transmission medium from a fault; an apparatus to measure at least one electrical property of the power transmission medium; and a controller programmed to determine the direction of the electrical fault; determine whether the electrical fault is an internal or external fault; and operate the protection device to protect the DC power transmission medium if the determination of the direction of the electrical fault and/or the determination of whether the electrical fault is an internal or external fault meet a predefined criterion.

Abstract: A DC distance protection scheme for protecting a DC power transmission medium within the DC electrical power network. The DC distance protection scheme includes a protection device that is coupled in use to a DC power transmission medium. The protection device is operable to protect the DC power transmission medium from an electrical fault. The DC distance protection scheme also includes a measurement apparatus to selectively measure the current and voltage of the DC power transmission medium. In addition the DC distance protection scheme also includes a controller that is programmed to calculate an operating voltage of the DC power transmission medium using the measured current and voltage; perform a transient comparison between the calculated operating voltage and the measured voltage; and operate the protection device to protect the DC power transmission medium if the transient comparison meets a predefined criterion.

Abstract: An apparatus for determining a fault location distance or distance protection in a multi-phase power transmission medium, configured to; determine a set of line fault parameters based on a measurement of voltage and current at a point of said power transmission medium and a fault type, the line fault parameters determined at a plurality of sample times determine a derivative with respect to time of a line fault parameters representative of an inductive part of measured faulty phase current; determine a set of phasors using a Fourier transformation of the derivative and of the remaining line fault parameters at the plurality of sample times and use said set of phasors to determine a fault location distance or distance projection distance along the power transmission medium; wherein, the determination of the fault location distance or the distance protection distance is based on the line equation; U . P = U . F + [ R 1 ? I . PR + X 1 ? 0 ? I . PX ] ? D F .

Abstract: A method of determining a communication time delay in a communication network between a local terminal and one or more remote terminals within an electrical power network includes: selecting, in respect of the or each remote terminal a calculation node in the electrical power network; calculating respective node currents flowing into the corresponding calculation node from the local terminal and the or each remote terminal; equating, in respect of the or each remote terminal, a sum of node currents flowing into the corresponding calculation node to zero according to Kirchhoff's first law; and extracting, in respect of the or each remote terminal, a communication time delay between the local terminal and the said respective remote terminal from a corresponding equated sum of node currents.

Abstract: A circuit interruption apparatus, for an electrical network, comprising a circuit interruption device that is operatively connectable at a source side to a source of the electrical network and at a back side to a load of an electrical network. The circuit interruption device when closed permits and when open inhibits the current flow between the source side the back side,. The current interruption device is configured to open when a current flowing therethrough meets or exceeds a fault current threshold. The circuit interruption apparatus also includes a fault current level determination unit that is configured to determine a predicted fault current level as a function of measured current and voltage values at the circuit interruption device before and after a variation in the current and voltage values at the circuit interruption device that result from a change of load at the back side of the circuit interruption device.

Abstract: A trip apparatus for a circuit interruption device that comprises a coil operatively connectable to a circuit interruption device. The coil is configured to selectively operate the circuit interruption device to interrupt when a current flowing through the circuit interruption device exceeds a threshold. The trip apparatus also includes a current measuring device configured to selectively measure a coil current flowing through the coil to determine a measured coil current signal. In addition, the trip apparatus includes a monitoring device configured to determine the derivative of the measured coil current signal and to perform a correlation of the derivative of the measured coil current signal and a reference derivative of a reference coil current signal to determine a correlation output. The monitoring device is further configured to compare the correlation output with a reference correlation threshold to determine whether an operating condition of the coil is normal or abnormal.

Abstract: An apparatus for determining a measure of the frequency of an electrical signal is provided. The apparatus is configured to, based on a plurality of samples of the electrical signal, determine a Hilbert transformation to obtain a value for each of the samples of the electrical signal for use as an imaginary representation of each of the samples of the electrical signal and combine each said imaginary representation with a corresponding real representation of the samples of the electrical signal to form a complex representation of the electrical signal; perform a Fourier transform on each said complex representation of the samples of the electrical signal and determine a phase angle therefrom; and determine a measure of the frequency of the electrical signal based on a derivative of the phase angle with respect to time.

Abstract: A method of determining a communication time delay in a communication network between a local terminal and one or more remote terminals within an electrical power network includes: selecting, in respect of the or each remote terminal a calculation node in the electrical power network; calculating respective node currents flowing into the corresponding calculation node from the local terminal and the or each remote terminal; equating, in respect of the or each remote terminal, a sum of node currents flowing into the corresponding calculation node to zero according to Kirchhoff s first law; and extracting, in respect of the or each remote terminal, a communication time delay between the local terminal and the said respective remote terminal from a corresponding equated sum of node currents.