A system and method for testing of electrical connections, conductors, and loads prior to energizing those connections is disclosed. For example, an interlocking socket can comprise a receptacle designed to be coupled to a connector of a load. The interlocking socket can comprise a microprocessor coupled to the receptacle, the microcontroller operable for testing one or more faults in the connector, a conductor, or the load coupled to the connector. In another example, a microprocessor can be coupled to a switch comprising a conductor, where the microprocessor is operable for testing one or more faults in the conductor or a load coupled to the conductor.

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.

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.

In a multi-phase power grid fed by a power source, earth fault (460) is located by means of a power supply source synchronized with the power grid, which is connected between a zero point of the grid and earth. In a fault current compensation mode (420), a control unit controls the alternating voltage source to compensate for any ground fault current in the power grid to a value below a threshold level. In a fault detecting mode (430), the control unit gradually adjusts the output voltage of the alternating voltage source with respect to amplitude and/or phase angle (440). A change of zero-sequence current and zero-sequence admittance between the alternating voltage source and a fault location is measured (450) by means of at least one detector. The at least one detector is communicatively connected to the control unit and reports recorded measured values representing zero-sequence current and/or zero-sequence admittance to the control unit. In the fault detecting mode, the control unit localizes a ground fault (460) based on at least one of said measurement values representing changes of the zero-sequence current and/or zero-sequence admittance, upon which an affected branch is disconnected (470) or the system switches to the fault compensation mode (420).

A method detects a high-impedance ground fault in an electrical energy supply network with a grounded neutral point. A test signal is fed via a detection device into the energy supply network, the test signal has a frequency which differs from the network frequency of the energy supply network. To enable a reliable detection, with low equipment costs, of high-impedance ground faults in energy supply networks with a grounded neutral point, a three-phase test signal is fed into the phase conductors of the energy supply network as the test signal. A measuring signal which indicates the residual voltage of the test signal is generated with the detection device. The residual voltage is compared with a threshold value using a test device of the detection device, and the presence of a high-impedance ground fault is detected if the residual voltage exceeds the threshold value.

An electrical link including a protective sheath surrounding at least two conductors each covered by an insulating jacket and an electrical protection system includes: a conductive sheath on each of the insulating jackets, a circuit breaker for each conductor; a direct current generator generating a direct current to be successively applied to each conductive sheath; and a leakage current detection circuit for each conductive sheath; a sequencer successively supplying the direct current to each conductive sheath; the detection circuit measures a current in each conductive sheath and compares a voltage proportional to the current to a first and second ranges of values, the detection circuit activating the circuit breaker if: the voltage is outside of the first range of values while the current generator generates a non-zero current; or the voltage is outside of the second range of values.

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.

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.

The invention relates to a method, electrical circuit arrangements and insulation monitoring devices for an interference-resistant insulation monitoring of an ungrounded power supply system having a converter.

Switching-frequent interfering signals, which are caused by operating the converter, are identified and assessed in a measured displacement voltage independently of the detection of a measuring signal in order to derive a switching (off) signal if required.

Complementary thereto, an interfering resistance with respect to low-frequency interfering portions generated by the converter is attained by these low-frequency interfering portions being generated from a replica of a pulse width modulation signal of the converter and being suppressed sufficiently via subtraction that a monitoring without gaps (frequency) of the insulation resistance becomes possible.

A monitoring system is applied to an electrical system, which includes a DC power source and an electrical apparatus that is connected to the DC power source by a pair of electric power leads incorporating respective switches. To detect leakage current from the DC power source, a low-frequency AC signal is applied via a large-capacitance capacitor to a specific connection position, between a first terminal of the DC power source and the corresponding switch, and the resultant voltage of that signal is measured. To detect a short-circuit failure of one or both of the switches, a high-frequency AC signal is applied via a low-capacitance capacitor to the specific connection position, and the resultant signal voltage is measured. Judgement as to occurrence of leakage current and/or short-circuit failure is based on the measured signal voltage values.