A sensor assembly includes a sensor generating a sensor signal, an output unit and a condition unit receiving the sensor signal output from the sensor, and a test line connected to the sensor and the condition unit. The output unit outputs a signal output representative of a state detected by the sensor. The condition unit outputs a condition output representative of a condition of the sensor. The test line is bidirectional and outputs the condition output.

A detection scheme for temporary overvoltages and/or ground fault overvoltages in electric power systems is described. Current passing through a surge arrestor component of the power system is monitored. An algorithm for identifying one or more frequency components of the measured current signal is performed to screen out unwanted harmonics. In some embodiments, this is a frequency domain analysis. The frequency component(s) of the current signal is then compared to a calculated pickup current or pickup voltage of the system to determine if system protection steps should be undertaken.

Some embodiments describe a DC meter system that can be placed in-line between a power source and an electrical load. In some embodiments, the DC meter system includes a DC meter that has multiple inputs for receiving electricity from multiple power sources. In some embodiments, the DC meter has one or more outputs, each capable of delivering electricity to a different electrical load. In some embodiments, the DC meter can combine electricity from two or more of the multiple inputs into one of the outputs. In some embodiments, the DC meter has a controller that can enable a user to deliver electricity from a particular input to a particular output. In some embodiments, the DC meter is configured to enable transition of electricity between an input and an output in a bi-directional manner. In some embodiments, the DC meter can record an amount of electricity transmitted in either direction.

Systems and methods for detecting an arc fault in a circuit breaker use a single-coil current rate of change (di/dt) sensor for monitoring both low frequency alternating current (AC) and broadband high frequency noise on a power line. The di/dt sensor is optimized to amplify any broadband high frequency noise, typically from about 1 MHz to 40 MHz, that may be present on the power line. Low frequency signals representing the current being monitored, typically from about 1 Hz to 10 KHz, is provided to an active integrator circuit with a high gain to enable the single-coil sensitivity. To shorten capacitor charge up time of the active integrator circuit, a charging current is provided to the active integrator circuit upon startup of the circuit breaker.

A current sensor system for accurately measuring an AC electrical current having frequencies up to 2 kHz, the system comprising: an electrical conductor (e.g. busbar) for conducting said AC current thereby creating a first magnetic field; a magnetic sensor device for measuring a magnetic field component or gradient; an object (e.g. a metal plate) having an electrically conductive surface arranged in the vicinity of said conductor for allowing eddy currents to flow in said surface, thereby creating a second magnetic field which is superimposed with the first magnetic field; wherein the magnetic sensor device is configured for determining the current as a signal or value proportional to the measured component or gradient. The metal plate may have an opening. The current sensor system may further comprise a shielding.

Example embodiments of the invention include a powdered core bead body configured to become an inductive impedance to current signals in a power wire with high frequencies. The signals are detectable by a high frequency voltage sensor, which is configured to output an arc fault tripping indication to an arc fault tripping circuit. The bead body includes a magnetic flux-density sensing device embedded in an air cavity of the bead body, having a magnetic field sensing surface oriented substantially perpendicular to the circumferential periphery of the bead body. The bead body is configured to provide measurable magnetic flux through the magnetic flux-density sensing device, for currents in the power wire having low frequencies. The measurable magnetic flux is detectable by a low frequency magnetic flux-density sensing device, to output a low frequency current measurement for power metering devices or to determine power consumption within a protected branch.

A current detector and a detection unit are provided. The current detector is connected to at least one of drive current lines of a rotary machine. The detection unit performs an orthogonal detection on a main frequency detected by the current detector, and extracts a magnitude of a sideband wave. Then, a state of the rotary machine is diagnosed from the magnitude of the extracted sideband wave.

A measurement module uses harmonic compensation factors to minimize the effects of harmonic distortion in measurements of a source current by a current sensor of the module. The module samples at a first sampling rate, measurements of the source current to generate a first current measurement. The module samples at a second sampling rate higher than the first sampling rate, for an interval of time, measurements of the source current to generate a second current measurement. The module determines a harmonic compensation factor based, at least, on a difference between the first current measurement and the second current measurement. The module determines a reported current computed as a function of at least the first current measurement, the difference between the first current measurement and the second current measurement, and the harmonic compensation factor. The reported current represents a magnitude of the source current adjusted by the harmonic compensation factor.

In a circuit breaker arrangement, this disclosure describes a method and circuit design enables a current transformer to be used to detect ground faults in circuit breakers (such as a main-tie-main circuit breakers) that have been designed to receive signals from Rogowski coils.

A current transformer (CT) for the purpose of, for example, current measurement, that uses a power line as a first coil and a second coil for measurement purposes, is further equipped with a third coil. Circuitry connected to the third coil is adapted to measure a signal therefrom. The measured signal from the third coil is compared to a signal measured from the second coil and based on the results, internal CT parameters are determined allowing calibration of actual results to expected results thereby providing an improved accuracy. This is especially desirable when using the CT for measurement of the like of current or phase of the primary coil when measurements are adjusted using the newly determined calibration parameters.