A time-admittance fault detection and isolation system includes a series of time-admittance switches spaced apart along the power line, each including a respective time-admittance function. Together, the time-admittance functions define a cascade trip sequence in a downstream-to-upstream direction, which autonomously causes a closest upstream time-admittance switch to a fault to trip to isolate the fault on an upstream side of the fault without communication with the time-admittance switches. The fault detection and isolation system may also include a radio communicating a trip signal from the closest upstream time-admittance switch to the fault to a closest downstream time-admittance switch to the fault. The trip signal causes the closest downstream time-admittance switch to the fault to trip to isolate the fault on a downstream side of the fault. A tie switch closes to back-feed a portion of the electric power line downstream from the closest downstream time-admittance switch to the fault.

A method for detecting fault in a power transmission line of a power transmission system and protection system using the same. The method includes: obtaining a system parameter of the power transmission system, adjusting protection reachability of a fault detecting element based on the obtained system parameter such that the adjusted protection reachability of the fault detecting element is applicable to a predetermined protection range, identifying whether there is an internal fault occurring on the transmission line using the adjusted fault detecting element, and generating a fault detection decision signal indicating the identified fault. If the predetermined protection range is desirable for the fault detecting element, its protection reachability may be adjusted in consideration of the influence imposed by the SIR such that the reach point of the adjusted fault detecting element can be extended to approach the end of the predetermined protection range. Consequently, the influence on its accuracy by various SIR values can be taken into account and accordingly the fault detecting solution can remove substantial errors as a result thereof.

A method for detecting fault in a power transmission line of a power transmission system and protection system using the same. The method includes: obtaining a system parameter of the power transmission system, adjusting protection reachability of a fault detecting element based on the obtained system parameter such that the adjusted protection reachability of the fault detecting element is applicable to a predetermined protection range, identifying whether there is an internal fault occurring on the transmission line using the adjusted fault detecting element, and generating a fault detection decision signal indicating the identified fault. If the predetermined protection range is desirable for the fault detecting element, its protection reachability may be adjusted in consideration of the influence imposed by the SIR such that the reach point of the adjusted fault detecting element can be extended to approach the end of the predetermined protection range. Consequently, the influence on its accuracy by various SIR values can be taken into account and accordingly the fault detecting solution can remove substantial errors as a result thereof.

In a digital-electricity power system, an electrical-current sample value is acquired along with a voltage sample value within a time window over which the electrical current and voltage are substantially unchanged. A transmission-line series voltage is derived from the difference between the voltage at the transmitter and the voltage at the receiver. Each transmission-line series voltage is divided by a corresponding stored electrical-current sample value to generate a ratio indicative of transmission-line series resistance. These steps are repeated, and the transmitter-disconnect device is placed in a non-conducting state if a difference in the ratio generated in one or more time periods exceeds a predetermined maximum, wherein exceeding the predetermined maximum is indicative of a series resistance fault. Alternatively, a series resistance value, determined by dividing a change in voltage over a change in current, is evaluated to detect a fault.

In a digital-electricity power system, an electrical-current sample value is acquired along with a voltage sample value within a time window over which the electrical current and voltage are substantially unchanged. A transmission-line series voltage is derived from the difference between the voltage at the transmitter and the voltage at the receiver. Each transmission-line series voltage is divided by a corresponding stored electrical-current sample value to generate a ratio indicative of transmission-line series resistance. These steps are repeated, and the transmitter-disconnect device is placed in a non-conducting state if a difference in the ratio generated in one or more time periods exceeds a predetermined maximum, wherein exceeding the predetermined maximum is indicative of a series resistance fault. Alternatively, a series resistance value, determined by dividing a change in voltage over a change in current, is evaluated to detect a fault.

Examples for protecting a power transmission line in response to a fault occurring within a monitored zone in a power transmission system are described. In an example, an occurrence of the fault in at least one phase of the power transmission line may be identified. Thereafter, an actual rate of change of incremental current is calculated based on calculated incremental currents. With the actual rate of change determined, a threshold for rate of change of incremental current is calculated based on calculated incremental voltages, the calculated incremental currents, line parameters, and a zone setting for the monitored zone. Based on comparison of the actual rate of change and the threshold for the rate of change, the fault is determined to have occurred in the monitored zone. Thereafter, a trip signal may be generated for controlling a switching device associated with the power transmission line.

Systems, methods, and computer-readable media are disclosed for high-speed falling conductor protection in electric distribution systems. An example method may include calculating, by a processor, at a first time, and for each phase, one or more first impedance values associated with one or more terminals of a transmission line. The example method may also include calculating, by the processor, at a second time, and for each phase, one or more second impedance values associated with the one or more terminals. The example method may also include determining, by the processor, that a rate of change of an impedance of the one or more terminals is greater than a threshold rate of change. The example method may also include determining, by the processor and based on the determination that the rate of change of the one or more terminals is greater than the threshold rate of change, that the transmission line has broken. The example method may also include sending, by the processor and based on the determination that the transmission line has broken, a signal to de-energize the transmission line before a broken conductor reaches a ground surface.

Distance protection for electric power delivery systems that include an unconventional source is disclosed herein using apparent impedance independent of memory and cross-phase polarizing. The apparent impedance may be compared with an offset distance operating characteristic. Fault direction is determined by using zero-sequence ground directional logic for phase-to-ground faults. For phase-to-phase faults, fault direction is determined using weak-infeed directional logic. Fault direction may further use incremental quantity directional principles. The distance protection may further determine a faulted loop using voltage logic. The distance protection may select between traditional distance protection and the methods described herein based on the current feeding the fault.

A method is provided for operating an inverter of an inverter-based power resource providing electric power to a grid through one or more transformers. The method includes measuring voltages associated with terminals on a selected primary winding and/or measuring voltages associated with terminals on a selected secondary winding; and injecting currents into the primary terminals of the selected primary winding during a fault condition based on the measured voltages being indicative of the type of fault occurring. Preferably the inverter is operated to emulate at least some characteristics of fault currents provided by a generator having rotating magnets or electrical windings. An apparatus is configured to operate in accordance with the method and includes an electrical switching device circuit having input terminals for an inverter-based power resource and output terminals for providing AC electric power to an electric power grid. An inverter controller operates the electrical switching device circuit.

A method is provided for operating an inverter of an inverter-based power resource providing electric power to a grid through one or more transformers. The method includes measuring voltages associated with terminals on a selected primary winding and/or measuring voltages associated with terminals on a selected secondary winding; and injecting currents into the primary terminals of the selected primary winding during a fault condition based on the measured voltages being indicative of the type of fault occurring. Preferably the inverter is operated to emulate at least some characteristics of fault currents provided by a generator having rotating magnets or electrical windings. An apparatus is configured to operate in accordance with the method and includes an electrical switching device circuit having input terminals for an inverter-based power resource and output terminals for providing AC electric power to an electric power grid. An inverter controller operates the electrical switching device circuit.