An embodiment relates to a switchgear for a single-phase motor and a three-phase motor, the switchgear including a processing unit and a first, second and third current path, the first and third current path each including a current transformer. The processing unit is adapted to detect the current I.sub.1 of the first current path and the current I.sub.3 of the third current path. To provide a cost-effective switchgear for a one-phase motor and a three-phase motor which is adapted to identify the failure of every single phase in the three-phase operation and a phase failure in the one-phase operation, the processing unit is designed such as to detect the currents I.sub.1, I.sub.3 of the first and third current path and to determine, based on the phase shift between the detected currents I.sub.1, I.sub.3 of the first and third current path in which operating mode the switchgear is operated.

An embodiment relates to a switchgear for a single-phase motor and a three-phase motor, the switchgear including a processing unit and a first, second and third current path, the first and third current path each including a current transformer. The processing unit is adapted to detect the current I.sub.1 of the first current path and the current I.sub.3 of the third current path. To provide a cost-effective switchgear for a one-phase motor and a three-phase motor which is adapted to identify the failure of every single phase in the three-phase operation and a phase failure in the one-phase operation, the processing unit is designed such as to detect the currents I.sub.1, I.sub.3 of the first and third current path and to determine, based on the phase shift between the detected currents I.sub.1, I.sub.3 of the first and third current path in which operating mode the switchgear is operated.

A system (e.g., a monitoring device) for monitoring a first battery (e.g., a vehicle battery) provided in a vehicle is provided with a monitoring unit for monitoring the electric state of the first battery (e.g., the vehicle battery) capable of starting a motor of the vehicle; and a power supply unit that is a second battery for supplying electric power to the monitoring unit. The monitoring unit may determine whether or not the motor is stopped, and when the motor is stopped, the monitoring unit may monitor, as the electric state of the first battery, e.g., the voltage of the first battery.

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 is a grid-connected inverter safety detection device applied in a photovoltaic inverter system and including voltage detection circuit, a filter circuit, a comparison circuit and a controller. The voltage detection circuit is configured to detect a voltage between the point N and the ground, or a voltage between the first terminal for any phase of the three-phase power grid and the ground. The filter circuit is configured to filter out an alternating current component of the voltage detected by the voltage detection circuit and to retain an direct current component of the voltage. The comparison circuit is configured to compare the direct current component of the voltage with a preset voltage value and transmit a comparison result to the controller. The controller is configured to determine, according to the comparison result, whether an alternating current side at the output terminal of the inverter has normal insulation.

A method and apparatuses for handling delayed zero crossing in fault current through a circuit breaker are disclosed. An interface arrangement is configured to couple an alternating current, AC, power system with a direct current, DC, power system, or vice versa. The interface arrangement includes at least one converter for conversion of AC power to DC power, or vice versa, which includes a DC side for coupling of the converter to the DC power system and an AC side for coupling of the converter to the AC power system. A circuit breaker is arranged in a current path between the AC side of the at least one converter and the AC power system. There may be a risk of delayed zero crossing in fault current occurring in case a fault occurs in a predefined portion of the interface arrangement. If a fault is sensed to occur in the interface arrangement within the predefined portion of the interface arrangement, opening of contacts of the circuit breaker can be delayed by a selected delay time period, compared to if the fault would have been within a portion of the interface arrangement different from the predefined portion.

A method for protecting a low-voltage distribution network. The low-voltage distribution network includes a low-voltage side of a three-phase distribution transformer that is configured to supply electrical power to at least one single-phase load through a respective distribution line of a plurality of three-phase distribution lines distribution lines. The method includes measuring variations of a periodic neutral-to-ground voltage between a neutral terminal of the three-phase distribution transformer and a local ground node by sampling the variations at a sampling frequency, detecting a fault in the low-voltage power distribution network based on the variations of the periodic neutral-to-ground voltage, and disconnecting the low-voltage side from the low-voltage power distribution network responsive to the fault being detected.

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.

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.

A matrix converter includes one or more current sensors structured to sense current flowing through the matrix converter, a matrix of switches including a number of solid state transistors, and a control circuit structured to detect faults in power flowing through the matrix converter based on the sensed current, to control the matrix of switches to drive an external device, and to control the matrix of switches to switch to prevent power from flowing internal to the matrix converter, or external to the external device in response to detecting a fault in power flowing through the matrix converter.