A system includes a generator. Three AC feeders are connected for feeding AC output from the generator. A rectifier is electrically connected to the three AC feeders and to a load via a first DC feeder and a second DC feeder. A first resistor connects between a first one of the DC feeders and ground. A first voltage sensor is operatively connected to detect voltage across the first resistor. A second resistor connects between the second DC feeder and ground. A second voltage sensor is operatively connected to detect voltage across the second resistor. A controller is configured to monitor for changes in common mode voltage based on the input from the first sensor and from the second sensor, and to determine presence of a fault if change in the common mode voltage exceeds a predetermined threshold.

A differential protection method for monitoring a line of a power grid. Current phasor measured values are captured at the ends of the line and transmitted to an evaluation device which is used to form a differential current value with current phasor measured values temporally allocated to one another. Time delay information indicating the time delay between local timers of the measuring devices is used for the temporal allocation of the current phasor measured values captured at different ends, and a fault signal indicating a fault affecting the line is generated if the differential current value exceeds a predefined threshold value. The reliability of the time synchronization is further increased by forming a quotient of the current phasor measured values to form an asymmetry variable, that is used to check a transit time difference of messages transmitted via the communication connection in different directions.

A temporary power delivery system includes a power source, a booth stringer, and a portable GFCI device. The GFCI device is receives current from the power source by a first terminal and delivers current to the booth stringer by a second terminal. An electronic processor of the GFCI device compares a combined magnitude of current flowing through first and second phase conductors of the GFCI device to a magnitude of current flowing through a neutral conductor of the GFCI. The electronic processor also compares a first voltage between the first phase conductor and neutral conductor to a second voltage between the second phase conductor and neutral conductor. A circuit breaker of the GFCI device is opened if a difference between the combined magnitude of phase conductor current and neutral conductor current exceeds a first threshold or a difference between the first voltage and second voltage exceeds a second threshold.

Provided are a complex multifunctional relay system capable of complexly performing an overcurrent blocking function, an arc blocking function, and an earth leakage blocking function by a relay circuit, and a control method therefor. The complex multifunctional relay system includes an AC circuit including a hot line and a neutral line, a power control means connected in parallel to the hot line, insulation differential amplifiers circuit-connected to the hot line and the neutral line through current shunts, a microprocessor connected to the power control means and the insulation differential amplifiers to perform monitoring and control the power supply of the power control means, a first comparator connected to the current shunt and the insulation differential amplifier and connected to the microprocessor so as to check ground fault, and a second comparator connected between the current shunt/the insulation differential amplifier and the microprocessor so as to check arc fault.

An embodiment of the invention relates to a method for ground fault detection for low-voltage three-phase AC circuits having a neutral conductor, in which first to fourth analog current signals of the first to third phase conductors and of the neutral conductor of the three-phase AC circuit are ascertained that each contain the level or an equivalent of the level of the current. The analog current signals are time-division multiplexed, subjected to a/d conversion, and a sequence of time-division-multiplexed first to fourth digital current values present in first to fourth successive time frames form first to fourth current signals. Three of the four digital current signals are interpolated to ascertain interpolated current values. The current value of the time frame of the uninterpolated current signal and the interpolated current values for the time frame of the uninterpolated current signal are used for discovering the ground fault.

The invention relates to an electronic switching protection apparatus comprising:a phase current line and a neutral current line; a measurement sensor (1); an electronic protection tripping device electrically connected to the measurement sensor (1) for processing the acquisition signal and for issuing a protective trip control signal representative of the occurrence of a fault; a galvanic isolation mechanism (4) comprising first and second pairs of contacts, which is configured to be actuated by a control mechanism (30) or by an actuator (3), characterized in that the electronic protection apparatus comprisesan electronic switching unit (9) comprising a power electronic switching component (10, 11) which is arranged, respectively, on the phase current line, and is able and intended to be made to trip by the protective trip control signal representative of the occurrence of a fault in order to open the at least one electronic switching component (10, 11), in that the actuator (3) is configured to actuate the opening of the first and second pairs of contacts consecutively with the opening of the electronic switching component (10, 11), and in that the electronic protection apparatus comprises a housing (12) in modular format.

The invention relates to an electronic switching protection apparatus comprising:a phase current line and a neutral current line; a measurement sensor (1); an electronic protection tripping device electrically connected to the measurement sensor (1) for processing the acquisition signal and for issuing a protective trip control signal representative of the occurrence of a fault; a galvanic isolation mechanism (4) comprising first and second pairs of contacts, which is configured to be actuated by a control mechanism (30) or by an actuator (3), characterized in that the electronic protection apparatus comprisesan electronic switching unit (9) comprising a power electronic switching component (10, 11) which is arranged, respectively, on the phase current line, and is able and intended to be made to trip by the protective trip control signal representative of the occurrence of a fault in order to open the at least one electronic switching component (10, 11), in that the actuator (3) is configured to actuate the opening of the first and second pairs of contacts consecutively with the opening of the electronic switching component (10, 11), and in that the electronic protection apparatus comprises a housing (12) in modular format.

Provided are a complex multifunctional relay system capable of complexly performing an overcurrent blocking function, an arc blocking function, and an earth leakage blocking function by a relay circuit, and a control method therefor. The complex multifunctional relay system includes an AC circuit including a hot line and a neutral line, a power control means connected in parallel to the hot line, insulation differential amplifiers circuit-connected to the hot line and the neutral line through current shunts, a microprocessor connected to the power control means and the insulation differential amplifiers to perform monitoring and control the power supply of the power control means, a first comparator connected to the current shunt and the insulation differential amplifier and connected to the microprocessor so as to check ground fault, and a second comparator connected between the current shunt/the insulation differential amplifier and the microprocessor so as to check arc fault.

A conventional technique makes a configuration complicated. Provided is an apparatus including: a voltage measuring unit configured to measure each of instantaneous voltages of three-phase AC voltage; and a determination unit configured to determine a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value.

A conventional technique makes a configuration complicated. Provided is an apparatus including: a voltage measuring unit configured to measure each of instantaneous voltages of three-phase AC voltage; and a determination unit configured to determine a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value.