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 inject a known reference signal to the third coil of the CT. The injected reference signal, i.e., current, generates signals in the first and second coils of the CT. The signal generated in the second coil is compared using circuitry attached thereto to the reference signal. Based on the results, and the difference between the expected results and the actual results, updated calibration parameters are determined. These provide improved accuracy when using the CT, for example for measurement of the like of current or phase of the primary coil when measurements are adjusted using the newly determined calibration parameters.

A solid state power controller configured to supply electric power from a power supply to at least one load, comprises: a solid state switching device having a first terminal (D) connected to the power supply, and a second terminal (S) connected to the load, the solid state switching device configured to switch between an OFF operation mode in which the second terminal (S) is electrically disconnected from the power supply, and an ON operation mode in which the second terminal (S) is electrically connected to the power supply, and a load current detection unit configured to detect a load current through the solid state switching device; wherein the load current detection unit comprises a first load current amplifier and a second load current amplifier.

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.

A current detector includes: a current sensor that is constructed using a Rogowski coil, detects a current flowing in a measured object, and outputs a detection signal corresponding to a current value of the current; a transfer line that is constructed of a distributed constant line and transfers the detection signal; an impedance converting circuit that is provided between the current sensor and the transfer line and has an input impedance equal or substantially equal to a characteristic impedance of the current sensor; an integrator circuit that integrates the detection signal inputted via the transfer line and outputs an output signal indicating a current value of the current; and a resistance circuit that has a resistance value that is equal or substantially equal to a characteristic impedance of the transfer line and is connected in series between the transfer line and the integrator circuit.

The subject-matter relates to a method, performed by at least one apparatus, including: determining of a correction factor for at least one first voltage transformer arranged in a power grid, the correction factor being indicative of a correction for obtaining correct measured values measured by the at least one first voltage transformer, wherein the determining of the correction factor of the at least one first voltage transformer being performed at least partially based on a first measured voltage of the at least one first voltage transformer and a second measured voltage of the at least one first voltage transformer, wherein the second voltage of the at least one first voltage transformer is determined at least partially based on a known transfer function of at least one second voltage transformer and the first voltage of the at least one first voltage transformer is determined without taking into account the known transfer function of the at least one second voltage transformer; determining a calibration factor for the at least one first voltage transformer based at least in part on the determined correction factor; and outputting or causing the output of the determined calibration factor. The subject matter further relates to a correspondingly configured apparatus and a system.

A combination of a conductor, such as a busbar, and a device for measuring the AC voltage in the conductor, which device includes: an insulation layer arranged on the conductor; a capacitor plate arranged on the insulation layer and configured to position the capacitor plate at a fixed distance from the conductor to form a first capacitor; a second capacitor arranged electrically between the capacitor plate and ground to provide a capacitive voltage divider with the first capacitor; and a voltage measurer for measuring the voltage at the capacitor plate, the voltage measurer including a frequency measurer for measuring the frequency of the voltage in the conductor and an AC voltage calculator for calculating the AC voltage in the conductor based on the capacities of the first and second capacitors, the measured voltage, and the measured frequency.

A method and apparatus for simultaneously testing a component at multiple frequencies is disclosed. A digital processing circuit may generate a digital representation of a signal having a plurality of sine waves, each having a unique frequency. The digital representation may be converted into an analog signal, and applied to a device under test (DUT). A first analog-to-digital converter (ADC) may be coupled to measure voltages across the DUT, while a second ADC may be coupled to measure currents through the DUT. Voltage and current signals received by the first and second ADCs, respectively, may be converted into first and second digital values. Voltage and current values at each unique frequency are determined from the first and second digital values. Using the voltage and current values for each unique frequency, a frequency response of the component (e.g., an impedance) over a range of frequencies may be determined.

A vehicle includes: a plurality of electric loads that consume the dark current during parking of the vehicle and modulate the dark current; a battery sensor that senses the dark current output from a battery, demodulates the dark current modulated by the plurality of electric loads, identifies the dark current consumed by each of the plurality of electric loads based on the demodulated dark current, and identifies an electric load, which consumes excess dark current, based on the dark current consumed by each of the plurality of electric loads; and an integrated control device to alert a driver of consumption of the excess dark current of the identified electric load.

Apparatus (1) is for detecting electrical current in a support (2) for an overhead power line (3) adapted to carry AC electricity at a nominal frequency. The apparatus (I) comprises a first and a second electrical contact (16, 17). The first and second electrical contacts (16, 17) are adapted to be electrically coupled to the support (2) in spaced apart relationship, in use. A voltage detector (7) is coupled to the first and second contacts. A first voltage signal generator (11) is coupled to the first electrical contact (16) and is adapted to generate a voltage signal at a second frequency. A processor (15) is coupled to an output from the voltage detector (7). The voltage detector (7) is adapted to detect a first voltage differential between the first and second electrical contacts (16, I 7) at a first frequency corresponding to the nominal frequency, and to detect a second voltage differential between the two electrical contacts (16, 17) at the second frequency. The processor (15) receives the first and second voltage differentials, and the processor (15), dependant on the detected first and second voltage differentials, generates an output signal indicative of the presence of an electrical current in the support (2).

The disclosure relates to a device for measuring electrical current in an electrical conductor (2), the device comprising: a measuring circuit configured to be connected to the electrical conductor, the measuring circuit comprising: a resistor based measuring circuit comprising a resistor (10), a transformer based measuring circuit comprising a current transformer (20) comprising a primary coil (20a), connected in series with the resistor (10) of the resistor based measuring circuit, a first inverter (12) configured to transform a first digital signal using a transfer function being an inverse of a transfer function representing the resistor based measuring circuit; a second inverter (22) configured to transform a second digital signal using a transfer function being an inverse of a transfer function representing the transformer based measuring circuits; and a signal combiner (5) configured to combine the transformed first and second digital signals, thereby providing a digital signal representing the electrical current in the electrical conductor. The disclosure also relates to a method for measuring electrical current in an electrical conductor.