A system and method for interrupting power in a three-phase power system interrupts power in the faulted phase and the next sequential phase at high speeds, while interrupting power in the remaining phase at a normal operation speed. Limiting high-speed interruption to only two phases requires significantly less energy storage than implementing high-speed interruption in all three phases. When hybrid circuit interrupters are used, the need to wait for a zero-crossing in the current signal in order to initiate interruption operations is eliminated.

A ground fault detection apparatus is used to detect a ground fault of a three-phase UPS apparatus. The UPS apparatus includes a first filter circuit, an AC/DC conversion circuit, a DC bus, a DC/AC conversion circuit, and a second filter circuit coupled in sequence. The ground fault detection apparatus includes a detection circuit having a first detection end and a second detection end. The first detection end is coupled to the first filter circuit and the second filter circuit, and the second detection end is coupled to an equipment grounding point. The equipment grounding point is coupled to a neutral point of a three-phase power source, and the three-phase power source is coupled to the first filter circuit. The detection circuit indicates whether the UPS apparatus has a ground fault and a location where the ground fault occurs according to a detection voltage between the first detection end and the second detection end.

In an electrical distribution system including a solid-state circuit breaker (SSCB) and one or more downstream mechanical circuit breakers (CBs), a solid-state switching device in the SSCB is repeatedly switched ON and OFF during a short circuit event, to reduce a root-mean-square (RMS) value of the short circuit current. The resulting pulsed short circuit current is regulated in a hysteresis control loop, to limit the RMS to a value low enough to prevent the SSCB from tripping prematurely but high enough to allow one of the downstream mechanical CBs to trip and isolate the short circuit. Pulsing is allowed to continue for a maximum short circuit pulsing time. Only if none of the downstream mechanical CBs is able to trip to isolate the short circuit within the maximum short circuit pulsing time is the SSCB allowed to trip.

A power supply includes an I/O module configured to receive a high voltage DC input and output a high voltage DC, a plurality of DC converter modules configured to receive the high voltage DC output from the I/O module and output a low voltage DC output, and a plurality of AC inverter modules configured to receive the high voltage DC output from the I/O module and output a high voltage AC output. Each of the plurality of DC converter modules, each of the plurality of AC inverter modules and the I/O module may be mounted in a corresponding individual chassis. Each of the individual chassis may be configured to be stackable together into a single line replaceable unit (LRU). Each of the individual chassis may have an identically shaped outer frame.

A system and method for interrupting power in a three-phase power system interrupts power in the faulted phase and the next sequential phase at high speeds, while interrupting power in the remaining phase at a normal operation speed. Limiting high-speed interruption to only two phases requires significantly less energy storage than implementing high-speed interruption in all three phases. When hybrid circuit interrupters are used, the need to wait for a zero-crossing in the current signal in order to initiate interruption operations is eliminated.

The embodiments of the present invention disclose a line protection method and a related apparatus for a flexible grounding system of a power distribution network. The method comprises outputting a first compensation voltage by a voltage source of a flexible grounding device of each line of a target power distribution network in the case where a ground fault occurs in the target power distribution network; starting to calculate the zero-sequence impedance of each line in real time by the zero-sequence impedance protection device; after the first compensation voltage is output for a first output duration, outputting a second compensation voltage; calculating the zero-sequence impedance of each line in real time by the line zero-sequence impedance protection device; determining a fault line by the zero-sequence impedance protection device, and cutting off the fault line to isolate the ground fault after a trip for a preset time delay.

A method for preventing ground fault in a three-phase electric transmission line system caused by a line break, includes: providing a programmable relay protection system, including a plurality of relay devices on each line, programmed to include: preset parameter ranges of at least two electric operating conditions, at least one high sensitivity instantaneous undercurrent and at least one high sensitivity condition selected from line differential overcurrent and negative sequence overcurrent (and combinations thereof), the preset ranges being acceptable operating parameter ranges; monitoring; permitting closed circuit operation when all of the lines show that the two operating conditions are within the preset acceptable operating parameter ranges; tripping a circuit breaker on a broken line when that line shows that the two operating conditions are outside the preset parameter ranges; and shutting down power to the broken line before it otherwise causes a ground fault or other short circuit.

A method and an apparatus for use in an earth-fault protection in a three-phase electric network, the apparatus configured to detect a phase-to-earth fault in the three-phase electric network, to determine for each of the three phases of the three-phase electric network a phase current during the detected phase-to-earth fault or a change in the phase current due to the detected phase-to-earth fault, to determine an estimate of an earth-fault current on the basis of the determined phase currents or on the basis of the determined changes in the phase currents, to determine, if the estimate of the earth-fault current represents an actual earth-fault current or an apparent earth-fault current, and to determine, in response to determining that the estimate of the earth-fault current represents the actual earth-fault current, that the estimate of the earth-fault current is valid.

A system for detecting miswiring in an AC power supply for an appliance may comprise a phase sensor sensing the phase difference between the first and a second hot line powering heavy electrical loads therebetween, and a control module coupling to the phase and voltage sensors. The control module may identify a fault condition and may disconnect different electrical loads from the power supply in the fault condition.

A power-conversion device and a ground-fault-location-diagnosis method for determining ground-fault locations on a motor and a cable are disclosed. The power-conversion device includes a ground-fault-current-measurement unit, an interphase short-circuit current-measurement unit, and a ground-fault-location-determination unit. The ground-fault-current-measurement unit turns on all switches of either upper arms or lower arms of three half-bridge circuits, and measures output current values of a plurality of phases generated during the ON period. The interphase short-circuit-current-measurement unit turns on a switch of an upper arm of one phase of the three half-bridge circuits and a switch of a lower arm of a phase different from the one phase, and measures output current values of a plurality of phases generated during a period of time both switches are ON. The ground-fault-location-determination unit determines a ground-fault location based on output-current values measured by the ground-fault-current-measurement unit and the output-current values measured by the interphase short-circuit current-measurement unit.