A DC-component-based fault classification apparatus and method for a three-phase power distribution cable utilizes the reconstructed three-phase currents by measuring the magnetic field around the cable with an array of magnetic sensors arranged around the cable surface. A magnetic shield houses the magnetic sensors and blocks background magnetic fields. A data acquisition system acquires analog signals from the sensors and a processing system extracts DC components in the analog signals for the phases during the transient period after a fault. The potential DC components are extracted by mathematical morphology. These DC components arise in the faulted phases when a fault occurs since there is a large current change in the inductive power network.

A charging station for charging an electric energy storage means of an electric vehicle using alternating charging current, having a fault-current protective device and having a charging controller. The fault-current protective device is divided into its functional units, a differential-current monitoring unit forming an integral structural unit in the form of a charging-current controller and monitoring device in conjunction with the charging controller according to the invention. Alternatively, the fault-current protective device forms an integral structural unit in the form of a charging-current controller and protective device in conjunction with charging controller.

An inverter for a photovoltaic plant including one or more DC electric lines electrically connectable to corresponding photovoltaic strings of the photovoltaic plant. Each DC electric line includes a plurality of line conductors wherein it includes a coupling transformer having a first winding arrangement and a second winding arrangement magnetically coupled with another. The first winding arrangement includes one or more first winding conductors electrically connected with one or more line conductors of a corresponding electric line. The second winding arrangement includes one or more winding conductors magnetically coupled with the first winding conductors and it is adapted to provide first signals indicative of AC currents flowing along the DC electric lines and to exchange second signals along the line conductors of the DC electric lines by exploiting the magnetic coupling with the first winding arrangement.

The invention relates to a method for detecting a direct-current fault current in an electrical alternating-current circuit, wherein a rectifier unit (14) is connected to an alternating-current network (34) by means of a primary side (13) and provides a direct current on a secondary side (15) and wherein the alternating-current network (34) is protected by means of a fault-current circuit breaker (38), which interrupts the circuit if an alternating-current fault current greater than a specified alternating-current tripping threshold occurs. A direct-current fault current on the primary side (13) is measured and is compared with a specified direct-current tripping threshold. An alternating-current fault current is produced if the direct-current fault current lies above the tripping threshold. The invention further relates to a device (10) for detecting a direct-current fault current and to a charging apparatus (12) comprising such a device (10).

Control circuit includes a current sensor that is configured to detect alternating current transmitted through a power line. The alternating current includes an alternating current (AC) component and a direct current DC offset component. The control circuit also includes a filter sub-circuit that is configured to receive a sensor output from the current sensor that is representative of the AC component and the DC component. The AC component has a frequency higher than a frequency of the DC component. The filter sub-circuit is configured generate a DC output that is based on the DC component. The control circuit also includes an analysis sub-circuit that is configured to receive the DC output and determine that the DC output has passed a designated threshold. The analysis sub-circuit is configured to trip a relay or output a signal when the DC output passes the designated threshold.

A power switch is for interrupting an electrical circuit when current and/or current time span threshold values are exceeded. The power switch includes an energy converter, which on the primary side is connected to the electrical circuit, and on the secondary side provides an energy supply for at least one control unit of the power switch. The energy converter has a core having a remanence flux density (Br2) of less than 30% of the saturation flux density (Bs2) or a coercive field strength (Hc2) of less than 10 A/m.

A circuit for alternating current and direct current leakage detection. The circuit can achieve multiple functions such as direct current leakage detection, alternating current leakage detection, and leakage sampling link self-check. The circuit mainly comprises: an LDO module for converting an externally input power supply voltage into a voltage required for leakage detection; a frequency divider module for performing frequency division on a high-frequency clock signal; a logic control module for driving an MOS transistor and controlling the switching of different working modes; an MOS transistor driving module for driving an external leakage detection coil; a leakage detection coil for inducing alternating current and direct current leakage signals and a leakage self-check signal; a sampling resistor for converting the current signal flowing through the leakage detection coil into a voltage signal; a PGA module for amplifying a sampling signal; a gain control module for controlling a PGA amplification factor; an ADC module for performing digital-to-analog conversion of the signals; a DSP module for processing the alternating current and direct current leakage signals and the leakage self-check signal; and a current limiting module for limiting a loop current.

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.

The present invention provides a trip control circuit for a circuit breaker capable of breaking a circuit when a fault current occurs due to a DC current component, as well as an AC current. The trip control circuit comprises a current transformer that has a core allowing a circuit to pass through and a secondary coil for detecting a current flowing on the circuit and providing a current detection signal; an oscillation circuit section that configured to apply an electrical signal to the secondary coil to increase a slope of a hysteresis loop of the current transformer to allow the secondary coil to detect a DC current and an AC current; and a trip determining circuit section that configured to compare a current value indicated by the current detection signal with a predetermined reference current value.

A magnetic core is electromagnetically coupled to two conductors that allow an AC current to flow through. An exciter is configured to supply a winding with an excitation current that is an alternating current. A current detector is configured to detect a current flowing through the winding. A DC component detector is configured to detect a DC component level from the current detected with the current detector. Two contact elements are respectively disposed along the two conductors. A discrimination controller is configured to: turn the two contact elements on when the DC component level detected with the DC component detector is less than or equal to a threshold; turn the two contact elements off when the DC component level detected with the DC component detector is greater than the threshold; and turn the two contact elements off in de-energized condition.