Distance protection for electric power systems disclosed herein uses an operating signal and a sequence polarizing signal made up of a supervised sequence current and a supervised sequence voltage. The polarizing signal may be determined based on the fault type and may be weighted toward sequence currents or sequence voltages depending on the power system conditions. For phase-to-ground faults, the sequence currents may include negative-sequence and zero-sequence currents. For phase-to-phase faults, the sequence currents may include negative-sequence currents. The current portion of the sequence polarizing signal may be weighted based on detection of insufficient negative-sequence current magnitude, standing unbalance, current transformer saturation, open pole, three-phase fault, and the like. The distance elements described herein provides improved protection during real-world power system conditions and changes.

A method and system is provided for locating a fault in a mixed power transmission line. The method is implemented by an Intelligent Electronic Device (IED) of the mixed line. The IED detects a travelling wave from one or more signals received from one or more measurement equipment. Thereafter, the IED identifies a line section with the fault, and generates two or more estimates for the location of the fault based on a time difference between arrival of two peaks of the travelling wave, a velocity of propagation of the travelling wave in the line section identified with the fault, and a length of one or more line sections. The IED determines the location of the fault based on a comparison of each estimate with a threshold, wherein the threshold is estimated based on the one or more signals, equivalent source impedance of each source and total line impedance.

A method for detecting fault direction of transmission line of an AC power system and control system using the same. The method includes: sampling current values and voltage values of three phases at one end of the transmission line for a series of time points; for each of the series of time points, computing instantaneous symmetrical voltage components of the three phases based on the voltage value samples for the respective one of the series of time points; for each of the series of time points, computing instantaneous symmetrical current components of the three phases based on the current value samples for the respective one of the series of time points; for at least two of the series of time points, calculating energy directional elements each based on the respective ones of the computed instantaneous symmetrical voltage components and the respective ones of the computed instantaneous symmetrical current components; identifying the fault direction in consideration of the calculated energy directional elements; and generating a fault direction signal indicating the identified fault direction. Simulation results show the graph of the energy directional element calculated based on instantaneous symmetrical voltage components and instantaneous symmetrical current components exhibits distinctive characteristics either for forward or reverse fault. In consideration of such difference, by calculating the energy directional element at each sampling time point, the fault direction information may be identified accurately.

A method for detecting fault direction of transmission line of an AC power system and control system using the same. The method includes: sampling current values and voltage values of three phases at one end of the transmission line for a series of time points; for each of the series of time points, computing instantaneous symmetrical voltage components of the three phases based on the voltage value samples for the respective one of the series of time points; for each of the series of time points, computing instantaneous symmetrical current components of the three phases based on the current value samples for the respective one of the series of time points; for at least two of the series of time points, calculating energy directional elements each based on the respective ones of the computed instantaneous symmetrical voltage components and the respective ones of the computed instantaneous symmetrical current components; identifying the fault direction in consideration of the calculated energy directional elements; and generating a fault direction signal indicating the identified fault direction. Simulation results show the graph of the energy directional element calculated based on instantaneous symmetrical voltage components and instantaneous symmetrical current components exhibits distinctive characteristics either for forward or reverse fault. In consideration of such difference, by calculating the energy directional element at each sampling time point, the fault direction information may be identified accurately.

A method generates a classification signal classifying an electrical impedance. The time characteristic of the impedance is measured resulting in impedance values. Impedance change vectors whose direction describes the movement of the impedance in the complex impedance plane and whose length describes the amount of the respective impedance change are formed with temporally successive impedance values. A check is carried out to determine whether the impedance shows a directional, continuous impedance movement. In the event of a subsequently detected change of direction of the impedance movement, the reaching of a reversal point is inferred and the rotation of the impedance change vectors is monitored with the result of a formation of an angle of rotation measured value. A classification signal indicating a fault is generated if the impedance change vectors have rotated in the area of the reversal point through a predefined maximum angle of rotation.

A method and apparatus for suppressing the impact of a compensator on line distance protection is provided, wherein the method comprises: obtaining a first current of a line connected to a compensator or series converters in the compensator, and a first voltage of a bus connected to the compensator or the line connected to the compensator; exiting the series converters and series transformers if the first current is greater than a preset current threshold and a duration is greater than a first preset time threshold; exiting the series converters and the series transformers if the first voltage is less than or equal to a preset voltage threshold and duration is greater than a second preset time threshold set the output voltage of the series converters to zero, and if a second current of an element corresponding to the first current meets conditions which the first current needs to meet; and otherwise, canceling the setting of the output voltage of the series converters to zero and obtaining a first current if a second voltage of the line corresponding to the first voltage is greater than the preset voltage threshold and the duration is greater than a third preset time threshold.

A power device protection system comprising a front-end monitoring device to acquire electrical operation data at an input side of a power supply circuit, a controller to receive the electrical operation data from the front-end monitoring device, wherein the controller determines an electrical parameter of the power supply circuit based on the electrical operation data and a load at the output side of the power supply circuit, and wherein the controller compares the determined electrical parameter of the power supply circuit and a threshold value associated with a defined operating condition.

A protection relay comprises a digital processing unit including: a first filter to eliminate a DC component in the time-series data, the first filter having a first window length; a second filter to eliminate a DC component in the time-series data, the second filter having a second window length shorter than the first window length; and a coefficient calculation unit to multiply an amplitude value of an output signal of the first filter and an amplitude value of an output signal of the second filter by first and second coefficients respectively, and integrate multiplication results. An operation determination is performed based on an output of the coefficient calculation unit. The first coefficient is decreased and the second coefficient is increased when a failure of the power system is detected, and thereafter, the first coefficient and the second coefficient are changed with a lapse of time.

A protection relay comprises a digital processing unit including: a first filter to eliminate a DC component in the time-series data, the first filter having a first window length; a second filter to eliminate a DC component in the time-series data, the second filter having a second window length shorter than the first window length; and a coefficient calculation unit to multiply an amplitude value of an output signal of the first filter and an amplitude value of an output signal of the second filter by first and second coefficients respectively, and integrate multiplication results. An operation determination is performed based on an output of the coefficient calculation unit. The first coefficient is decreased and the second coefficient is increased when a failure of the power system is detected, and thereafter, the first coefficient and the second coefficient are changed with a lapse of time.

A method for identifying a location of a fault in an electrical power distribution network that includes identifying an impedance of an electrical line between each pair of adjacent utility poles, measuring a voltage and a current of the power signal at a switching device during the fault, and estimating a voltage at each of the utility poles downstream of the switching device using the impedance of the electrical line between the utility poles and the measured voltage and current during the fault. The method calculates a reactive power value at each of the utility poles using the estimated voltages, where calculating a reactive power value includes compensating for distributed loads along the electrical line that consume reactive power during the fault, and determines the location of the fault based on where the reactive power goes to zero along the electrical line.