It is proposed to use a spun birefringent fiber for a current sensor or magnetic field sensor. The fiber has a birefringence that increases with temperature. In this case, the temperature dependence of the fiber's sensitivity to magnetic fields counteracts the temperature dependence of the fiber's Verdet constant, which allows to design current and field sensors that have reduced temperature dependence.

A voltage sensor includes a vibrator configured to be supported by a mechanical supporting portion and to be given a floating potential, a drive electrode configured to be disposed adjacent to the vibrator and to resonate the vibrator with applied AC voltage, a driver configured to apply an AC voltage that crosses 0 V to the drive electrode, a fixed electrode configured to be disposed adjacent to the vibrator with a gap formed between the fixed electrode and the vibrator, and a calculator configured to detect a magnitude of a measurement target voltage based on a change of a resonant frequency of the vibrator when the measurement target voltage is applied to the fixed electrode.

A voltage sensor includes a vibrator configured to be supported by a mechanical supporting portion and to be given a floating potential, a drive electrode configured to be disposed adjacent to the vibrator and to resonate the vibrator with applied AC voltage, a driver configured to apply an AC voltage that crosses 0 V to the drive electrode, a fixed electrode configured to be disposed adjacent to the vibrator with a gap formed between the fixed electrode and the vibrator, and a calculator configured to detect a magnitude of a measurement target voltage based on a change of a resonant frequency of the vibrator when the measurement target voltage is applied to the fixed electrode.

The invention relates to an assembly of a gas-tight compartment and an optical voltage sensor that further comprises a module. The module comprises an electro-optic crystal and electrodes, wherein the electro-optic crystal is the only element of the module to mechanically connect the two electrodes and to bridge the potentials of the two electrodes. The assembly is particuarly suited to measure direct current voltages.

A voltage sensor includes an oscillator that has a circular or roughly circular shape and is supported by a mechanical support member, a fixed electrode that has a predetermined gap between the oscillator and the fixed electrode, and a drive electrode that is placed at a position different from the fixed electrode across the oscillator, and to which an AC drive voltage is applied to make the oscillator oscillate. In the voltage sensor, an electrostatic attractive force acts on the oscillator by applying a voltage to the fixed electrode, and a resonance frequency of the oscillator changes.

A method for distinguishing an arc from a luminous gas at least containing metal vapor includes sensing light in a monitoring region and determining a first intensity I.sub.1 of the sensed light at a first wavelength 1 and a second intensity I.sub.2 of the sensed light at a second, greater wavelength 2. The ratio I.sub.1/I.sub.2 between the first intensity I.sub.1 and the second intensity I.sub.2 is determined. The sensed light is associated with an arc if said ratio I.sub.1/I.sub.2 is greater than a specifiable first threshold value and/or with a luminous gas at least containing metal vapor if said ratio I.sub.1/I.sub.2 is less than a specifiable second threshold value.

It is described an arrangement for obtaining electrical state information related to an electrical power cable, the arrangement comprising: at least one current sensor arrangeable at at least one measurement location and adapted to generate a current sensor signal indicative of a value of an electrical current related to the electrical power cable; at least one electrical-mechanical transducer arranged in order to receive a current sensor signal based driving signal and adapted to generate a mechanical response at a response surface based on the driving signal; a distributed acoustic sensing equipment, comprising: at least one first optical fibre having a first end and a second end, a contact portion of the first optical fibre between the first end and the second end being mechanically in contact with the response surface; an interrogation system adapted to generate temporally successively optical pulses and coupleable to the first end of the first optical fibre in order to inject the optical pulses into the first optical fibre and adapted to detect first Rayleigh backscattered light returning from the first optical fibre in a time resolved manner; a processing portion adapted to process the detected first Rayleigh backscattered light in order to at least determine the value of the current.

It is described an arrangement for obtaining electrical state information related to an electrical power cable, the arrangement comprising: at least one current sensor arrangeable at at least one measurement location and adapted to generate a current sensor signal indicative of a value of an electrical current related to the electrical power cable; at least one electrical-mechanical transducer arranged in order to receive a current sensor signal based driving signal and adapted to generate a mechanical response at a response surface based on the driving signal; a distributed acoustic sensing equipment, comprising: at least one first optical fibre having a first end and a second end, a contact portion of the first optical fibre between the first end and the second end being mechanically in contact with the response surface; an interrogation system adapted to generate temporally successively optical pulses and coupleable to the first end of the first optical fibre in order to inject the optical pulses into the first optical fibre and adapted to detect first Rayleigh backscattered light returning from the first optical fibre in a time resolved manner; a processing portion adapted to process the detected first Rayleigh backscattered light in order to at least determine the value of the current.

A fiber-optic current sensor uses a highly-birefringent spun fiber as sensing fiber. The light is fed through a retarder, which is a detuned quarter-wave or half-wave retarder. It is shown that such detuning can be used to compensate for temperature dependencies of the sensing head.

A method and a sensor for measuring a time derivative of an AC current flowing through a measurement object are presented, wherein a Rogowski-Steinhaus-Chattock coil is aligned with the measurement object and at least one partitioning line is drawn into coil turns of the Rogowski-Steinhaus-Chattock coil and minimizes a capacitive coupling of the coil turns of the Rogowski-Steinhaus-Chattock coil among one another and/or to at least one further electrical line by virtue of the fact that an electrical potential corresponding to the electrical potential of the coil turns of the Rogowski-Steinhaus-Chattock coil is impressed on the at least one partitioning line by means of an active feedback.