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 system and method for differential protection is provided. Aspects includes determining a first current value associated with a first current transformer coupled to a first location in a differential protection zone, the first current transformer having a first transformer ratio, determining a second current value associated with a second current transformer coupled to a second location in the differential protection zone, the second current transformer having a second transformer ratio, and determining, by a controller, a type of fault associated with the differential protection zone based on the first current value and the second current value.

A system and method for differential protection is provided. Aspects includes determining a first current value associated with a first current transformer coupled to a first location in a differential protection zone, the first current transformer having a first transformer ratio, determining a second current value associated with a second current transformer coupled to a second location in the differential protection zone, the second current transformer having a second transformer ratio, and determining, by a controller, a type of fault associated with the differential protection zone based on the first current value and the second current value.

An interface control circuit complying with an interface specification includes: an interface signal transceiver circuit and a protection circuit. The interface signal transceiver circuit is coupled to a first interface connection pin and a second interface connection pin of a first interface connector circuit. The interface signal transceiver circuit is for transmitting and/or receiving an interface signal according to the interface specification. When the interface signal transceiver circuit operates under a first state, the protection circuit determines whether a foreign object exists between the first interface connection pin and the second interface connection pin according to a voltage change or a current change at the second interface connection pin. Under the first state, the interface signal transceiver circuit generates a pull-up signal and a pull-down signal which are toggled with each other at the first interface connection pin.

An interface control circuit complying with an interface specification includes: an interface signal transceiver circuit and a protection circuit. The interface signal transceiver circuit is coupled to a first interface connection pin and a second interface connection pin of a first interface connector circuit. The interface signal transceiver circuit is for transmitting and/or receiving an interface signal according to the interface specification. When the interface signal transceiver circuit operates under a first state, the protection circuit determines whether a foreign object exists between the first interface connection pin and the second interface connection pin according to a voltage change or a current change at the second interface connection pin. Under the first state, the interface signal transceiver circuit generates a pull-up signal and a pull-down signal which are toggled with each other at the first interface connection pin.

Techniques for determining whether a downed conductor is present in an electrical power distribution network that includes a neutral line and a plurality of energized conductors are disclosed. For example, a sampled neutral current signal is received, the sampled current signal including a plurality of values, each of the values representing an amplitude of current that flows in of the neutral conductor at a particular time; an unfiltered current signal is generated based on the sampled current signal; the sampled current signal is filtered to generate a filtered current signal; the unfiltered current signal and the filtered current signal are compared to generate an error signal; and the error signal is analyzed to determine whether at least one of the plurality of conductors is a downed conductor.

Techniques for determining whether a downed conductor is present in an electrical power distribution network that includes a neutral line and a plurality of energized conductors are disclosed. For example, a sampled neutral current signal is received, the sampled current signal including a plurality of values, each of the values representing an amplitude of current that flows in of the neutral conductor at a particular time; an unfiltered current signal is generated based on the sampled current signal; the sampled current signal is filtered to generate a filtered current signal; the unfiltered current signal and the filtered current signal are compared to generate an error signal; and the error signal is analyzed to determine whether at least one of the plurality of conductors is a downed conductor.

Systems and methods to disconnect a faulted region of a power grid are described. For example, a control system may obtain a set of regions of a power grid. The control system may obtain a current magnitude and a voltage magnitude of the power grid. The control system may detect a fault in the power grid based at least in part on the current magnitude. The control system may, from the set of regions, determine a faulted region that the fault is located within based on a voltage magnitude of one or more buses in the power grid, a net change in power with respect to time of one or more regions in the set of regions, or both. The control system may send one or more signals to electrically disconnect the faulted region from the power grid.

Systems and methods to isolate faults and restore power are described herein. For example, an intelligent electronic device (IED) may receive a blocking signal indicating a fault is detected on a power line. The IED may obtain one or more current measurements of the power line. The IED may determine that a fault is not present on the power line at the IED based on the one or more current measurements. The IED may trip a first current interruption device of the IED The IED may send a close permissive signal to another IED indicating that the other IED is permitted to permitted to close an open current interruption device of the other IED to restore power to one or more loads.

The invention provides a method and device for fault section identification in a multi-terminal mixed line. The method comprises obtaining positive sequence voltage and current phasors from measurements of voltages and currents at each terminal of the mixed line. The method further comprises calculating a voltage phasor for each terminal, wherein the calculation of the voltage phasor for a first terminal is performed using at least the voltage and current phasors obtained for one of a second terminal and a third terminal, and the current phasor obtained for the first terminal. Thereafter, the method comprises determining a section of the mixed line having the fault, based on comparison of the calculated and obtained voltage phasors for each terminal. In addition, the method comprises controlling a switching device with a re-trip signal generated based on the determination of the section with the fault.