A first voltage output unit generates a cyclic voltage that changes cyclically, and applies the cyclic voltage to the other end of a coupling capacitor via a first resistance. A second resistance and a third resistance are connected in series between a node and a second voltage output unit, the node being between the coupling capacitor and the first resistance. A voltage measurement unit measures a voltage at a voltage dividing point between the second resistance and the third resistance. In a period in which two types of fixed voltages are applied to the voltage dividing point in order, a diagnosing unit determines whether the leakage detecting device is in a normal state, based on the voltage measured by the voltage measurement unit.

A circuit interrupting device including a phase conductor, a neutral conductor, an interrupter configured to disconnect the phase conductor and the neutral conductor from a load, and a sensor configured to generate a signal indicative of current flowing through the phase conductor and the neutral conductor. The circuit interrupting device further includes a microcontroller that includes an electronic processor and is electrically connected to the first sensor and the interrupter. The microcontroller is configured to generate a reference signal, receive a first signal from the sensor, determine whether a difference between a voltage of the first signal and a voltage of the reference signal exceeds a threshold, determine whether the microcontroller has performed a ground fault self-test, and activate the interrupter when the difference exceeds the threshold and the microcontroller has not performed the ground fault self-test.

An apparatus and method for sensing a leakage current along a primary conductor are provided. A first fault detection module is deployed at a first location along the primary conductor and a second driver module is deployed at a second location along the conductor, where the conductor passes through current sensors at each of the modules. The modules are further linked by a safety cable, which also passes through the current sensors. The driver module drives a compensation current in the safety cable to drive the net current passing through the driver current sensor to zero. The fault sensing module senses the net current passing through its current sensor. When the sensed current deviates significantly from zero, the fault sensing module generates a leakage current indication signifying a potential ground fault between the two modules.

An electrical connector testing system can include a first connector end and a controller coupled to first connector end. The system can also include an electrical load coupled to the first connector end, where the electrical load includes an electrical cable and a second connector end coupled to an end of the electrical cable. The controller can determine whether an adverse electrical condition exists with respect to the electrical load before allowing power to flow between the first connector end and the second connector end.

An apparatus for monitoring ground current includes a signal generation module that generates a plurality of AC components of different frequencies. An injection module injects the plurality of AC components on one or more phases of a set of power cables connecting a power source to a load. The set of power cables includes an equipment grounding conductor. The AC components are injected in the equipment grounding conductor. An AC detection module that determines an AC current corresponding to each frequency of the AC components present in current in the equipment grounding conductor, an AC threshold module determines if one or more of the AC currents is below an AC threshold, and a trip module opens a contact if the AC threshold module determines that at least one of the AC currents is below an AC threshold. The contact disconnects the power source from the power cables.

A watchdog apparatus for monitoring ground current is disclosed. A system and method also perform the functions of the apparatus. The watchdog apparatus includes a watchdog signal module that generates a watchdog signal. The watchdog signal is generated at a specific interval and includes an identifiable characteristic. The watchdog signal module is part of a device being monitored for functionality. The apparatus, in some embodiments, includes a signal monitoring module that determines if the watchdog signal includes the identifiable characteristic, and an alert module that sends and alert signal in response to the signal monitoring module determining that the watchdog signal does not include the identifiable characteristic.

A watchdog apparatus for monitoring ground current is disclosed. A system and method also perform the functions of the apparatus. The watchdog apparatus includes a watchdog signal module that generates a watchdog signal. The watchdog signal is generated at a specific interval and includes an identifiable characteristic. The watchdog signal module is part of a device being monitored for functionality. The apparatus, in some embodiments, includes a signal monitoring module that determines if the watchdog signal includes the identifiable characteristic, and an alert module that sends and alert signal in response to the signal monitoring module determining that the watchdog signal does not include the identifiable characteristic.

A system includes a hot wire and a neutral wire configured to establish a closed circuit between a power source and a load. The system further includes first and second transformers as well as a sensor. The first current transformer is coupled to the hot wire and is configured to introduce a first test current, with a first polarity, into the hot wire. The second current transformer is coupled to the neutral wire and configured to substantially simultaneously introduce a second test current into the neutral wire. The second test current has the same polarity as the first test current. The sensor is configured to sense an asymmetry between the first and second test currents and is further configured to cause interruption of the closed circuit upon sensing the asymmetry.

Systems and methods for identifying an island condition in a power distribution system and disconnecting distributed generators in the case of islanding. The systems and methods are used to enable reliable detection of island formation with high false-trip immunity, for any combination of distributed energy resources, and for distributed energy resources using grid support functions.

The invention relates to an insulation monitoring device for simultaneously monitoring an ungrounded power supply system comprising network sections that can be interconnected via coupling switches, comprising a signal generator for generating a measuring signal and a coupling circuit for coupling the measuring signal to the power supply system. According to the invention, the insulation monitoring device comprises a coupling circuit for each interconnectable network section to be monitored, a switchable electrical connecting element being arranged for connecting adjacent coupling circuits.