A method for identifying element failure in capacitor banks is provided. Capacitor bank phase current is measured and a zero-sequence or negative-sequence current is calculated or measured. A three-phase voltage is measured from a three-phase bus voltage transformer and a zero-sequence voltage or negative-sequence voltage is calculated. A compensated unbalance current is calculated and compared to a predetermined acceptable range. A failure is identified where the compensated unbalance current is outside the predetermined acceptable range.

A device is provided that is suitable for use with a double-circuit power transmission system having a first line and a second line. The device comprises an interface to receive a current measurement for the second line. The device comprises at least one processing module operative to estimate a first zero-sequence current in the first line based on a second zero-sequence current, and determine an apparent impedance based on the estimated first zero-sequence current.

Provided are a ground fault protection method and apparatus for a photovoltaic station output transmission line. A circuit breaker on a photovoltaic side is controlled by a control element. Whether measured zero sequence impedance on the photovoltaic side of a segment line has a large variation before and after an action of power grid side distance protection is determined, the variation of the measured zero sequence impedance is inputted into the control element, in condition that the variation of the measured zero sequence impedance is less than a setting value, a tripping signal is outputted to the circuit breaker on the photovoltaic side to isolate the fault; and in condition that the variation of the measured zero sequence impedance is greater than the setting value, photovoltaic side distance protection is not started.

Provided are a ground fault protection method and apparatus for a photovoltaic station output transmission line. A circuit breaker on a photovoltaic side is controlled by a control element. Whether measured zero sequence impedance on the photovoltaic side of a segment line has a large variation before and after an action of power grid side distance protection is determined, the variation of the measured zero sequence impedance is inputted into the control element, in condition that the variation of the measured zero sequence impedance is less than a setting value, a tripping signal is outputted to the circuit breaker on the photovoltaic side to isolate the fault; and in condition that the variation of the measured zero sequence impedance is greater than the setting value, photovoltaic side distance protection is not started.

Systems, methods, and computer-readable media are disclosed for identifying a fault using systems and methods for a controlled dynamic MHO characteristic. Particularly, the systems and methods described herein may automatically control the dynamic expansion of the MHO characteristic based on the estimation of uncontrolled dynamic MHO expansion estimation and maximum allowable expansion set by a user. This may provide flexibility in that, the MHO can be allowed to expand to a maximum level, when the estimated MHO expansion value is below the user defined maximum allowable expansion level, but also provides a controlled dynamic MHO when the estimated values are above the maximum allowable level.

The present invention provides a method for current for fault identification in a transmission line and an apparatus thereof. The method comprises the following steps: measuring the real-time values of the currents and the voltages of the other unbroken healthy phase conductors when a single-phase fault occurs; calculating the inductive voltage and the capacitive coupling voltage according to the measured currents and voltages respectively; comparing the capacitive coupling voltage with the inductive voltage multiplied by a factor, in which the multiplication result is used as a self-adjusted threshold based on the real time load condition of the transmission line; and identifying the fault type based on the maximum of the capacitive coupling voltage and the multiplication.

A quadrilateral distance module may be used to detect faults in an electrical power system. A resistive coverage of the quadrilateral distance module may be defined by an adaptive resistance blinder. Tilt of the adaptive reactance element and resistance blinders may be limited. When an angle between the sequence-component based, current polarizing quantity and the element loop current does not exceed a predetermined angle threshold, the sequence-component based polarizing quantity may be used. Otherwise, the element loop current may be used to limit the tilt. Fault detection may comprise comparing both the adaptive resistance blinders for forward and reverse load flow conditions to power system stimulus and detecting a fault when the stimulus satisfy either blinder.