A system for detecting a fault type and faulted phase in a power grid includes a controller and a relay. The relay is configured to monitor a line of the power grid and generate a monitoring signal. The controller may be configured to determine, in response to the monitoring signal received from the relay, sequence voltages and sequence currents in the line. The controller may further determine, in response to the sequence voltages and sequence currents, an absence or a presence of a weak-infeed condition in the line. The controller may further determine, in response to the monitoring signal and the absence or the presence of the weak-infeed condition, a first plane sequence signature and a second plane sequence signature. The controller may further determine a fault type and faulted phase in the power grid in response to the first plane sequence signature and the second plane sequence signature.

A wireless power transmission device includes a transmitter unit and a receiver unit. The transmitter unit converts an input DC power into an inverted AC power, the receiver unit receives the AC power through a coupling effect. A fault protection method is also provided in the present disclosure. If the receiver unit is abnormal, a main power circuit of the receiver unit is short-circuited. Then, a phase relationship between an inverted AC voltage and an inverted AC current of the inverted AC power is detected. A phase judgment signal is generated according to the phase relationship. An overcurrent judgment signal is generated according to the amplitude of the inverted AC current and a predetermined current threshold. A fault signal is generated according to the phase judgment signal and the overcurrent judgment signal. In response to the fault signal, the wireless power transmission device is controlled to shut down.

A method for detecting the operating condition of each phase of a three-phase capacitor bank in a power distribution system, including the steps of, if the RMS neutral current is above the bank status closed setting, comparing the phase angle of neutral current (IN) with respect to voltage on one of the phases (VA, VB or VC) and sending an alarm signal when the comparison of the phase angle of neutral current with respect to the phase voltage differs appreciably from the expected phase angles.

In one embodiment, a network protector for a spot network includes a circuit breaker and a network protector relay coupled to the circuit breaker. The network protector relay is structured and configured to have network protector relay non-sensitive trip settings for controlling operation of the circuit breaker that will cause the network protector to remain closed when: (i) an angular difference () between a transformer phase-to-neutral voltage of the first feeder branch and a transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a first threshold value, and (ii) a magnitude difference () between the transformer phase-to-neutral voltage of the feeder branch and the transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a second threshold value.

In accordance with one embodiment, a method for detection of power swing for at least a first range of swing angles between an internal voltage (E.sub.S) of a source-end generator and an internal voltage (E.sub.R) of a receiving-end generator is provided. The method includes obtaining a voltage magnitude (V.sub.S) of the source-end generator, and a current magnitude (I.sub.S) of the source-end generator. The method further includes estimating a total reactance (X) between the source-end generator and the receiving-end generator, and estimating a first swing angle () between the E.sub.S and the E.sub.R as a function of the obtained V.sub.S, the obtained I.sub.S and the estimated X. The method further includes detecting a power swing condition based on the estimated .

A hybrid air-gap/solid-state device protection device (PD) for use in an electrical power distribution system includes an air-gap disconnect unit connected in series with a solid-state device, a sense and drive circuit, and a microcontroller. Upon the sense and drive circuit detecting an impending fault or exceedingly high and unacceptable overvoltage condition in the PD's load circuit, the sense and drive circuit generates a gating signal that quickly switches the solid-state device OFF. Meanwhile, the microcontroller generates a disconnect pulse for the air-gap disconnect unit, which responds by forming an air gap in the load circuit. Together, the switched-OFF solid-state device and air gap protect the load and associated load circuit from being damaged. They also serve to electrically and physically isolate the source of the fault or overload condition from the remainder of the electrical power distribution system.

A network protector includes a resettable switching apparatus configured to electrically connect to a low-voltage feeder of a secondary distribution network; a switch control configured to control a state of the resettable switching apparatus to thereby determine whether electrical current flows through the switching apparatus; and a controller configured to: determine whether a fault condition exists; and if a fault condition does not exist, allow electrical power to flow through the resettable switching apparatus in any direction.

The present disclosure discloses a complex fault protection method and system for a single return line of an arc suppression coil ground system. The method determines whether a ground fault occurs in the corresponding line based on a negative sequence measurement impedance angle or a negative sequence measurement admittance angle of the line in the arc suppression coil ground system. The system is used to implement the above method. The complex fault protection method of the present disclosure can provide protection for the complex fault situation where two points in a single return line are grounded out of phase and is not affected by factors such as the fault position and the transition resistance. Furthermore, the complex fault protection method also has a strong anti-interference ability and a high stability, applicability and sensitivity.