General Electric Technology Gmbh

Sankara Subramanian Sri Gopala Krishna Murthi

Hengxu Ha

Yongyue Ma

Xia Yang

Lianfu Yu

Gajendiran Balakrishnan

Xianwu Zeng

Shiming Fang

Botong Li

Wentao Huang

Gengxu Ha

Shi Fang

Brian Kirby

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 (&#x3b4;)}) between a rotor angle (&#x3b4;) of an individual one of the plurality of generators and an equivalent rotor angle (&#x3b4;) of the centre of inertia of the remainder of the plurality of generators; (b) processing the differential value ({tilde over (&#x3b4;)}) to determine whether the differential value ({tilde over (&#x3b4;)}) is predicted to reach a predefined reference threshold (&#x3b4;); and (c) predicting the presence of the out-of-step condition in the power system if the differential value ({tilde over (&#x3b4;)}) is predicted to reach the predefined reference threshold (&#x3b4;).

System and method of predicting the presence of an out-of-step condition in a power system

A DC distance protection controller for identifying a fault within a protection zone that extends between a first terminal and a set point along a DC power transmission conduit which lies between the first terminal and a second terminal within a DC electrical power network. The protection controller periodically obtains as respective sampled pairs a measured voltage value and a measured current value of the DC power transmission conduit; isolates a fault component voltage value and a fault component current value to define a respective corresponding isolated pair; calculates from each isolated pair a fault component operating voltage of the DC power transmission conduit at the set point; compare a given calculated fault component operating voltage with a historical voltage value; and identifies a fault within the protection zone when the given calculated fault component operating voltage is greater than the historical voltage value.

Direct current distance protection controllers

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.

Method of locating a fault in a power transmission scheme

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.

Systems and methods for determining a time delay in electrical power systems

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; 

Fault location detection and distance protection apparatus and associated method

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.

Circuit interruption apparatuses

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.

Direct current distance protection schemes

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.

Relating to direct current protection schemes

In the field of multi-terminal electrical power network protection, a protection apparatus comprises a measurement apparatus to measure the respective terminal current (I, I, I, I, I, I) flowing at each terminal (L, R, R, R, R, R) in a multi-terminal network that includes a plurality of electrically interconnected terminals (L, R, R, R, R, R). The protection apparatus also includes a control unit that is programmed to process the measured terminal currents (I, I, I, I, I, I) to obtain first and second summed values (I(n), I(n)). The first summed value (I(n)) is the sum at a given time (n) of the or each terminal current (I, I, I, I, I, I) flowing in a first direction (Di) relative to a corresponding terminal (L, R, R, R, R, R) and the second summed value (I(n)) is the sum at the same given time (n) of the or each terminal current (I, I, I, I, I, I) flowing in a second direction (D) opposite the first direction (D) relative to the corresponding terminal (L, R, R, R, R, R). The control unit is further programmed to compare the phase of the first summed value (I(n)) with the phase of the second summed value (I(n)) to determine whether a fault in the multi-terminal network is internal or external to the multi-terminal network and thereafter to produce an internal fault output signal upon the determination of an internal fault.

Protection apparatus

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.

Apparatus for determination of the frequency of an electrical signal and associated methods

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.

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Stafford, United Kingdom

Sankara Subramanian Sri Gopala Krishna Murthi