The invention enables the measurement of the voltage between phases (phase-to-phase voltages) of a multi-phase power cable, e.g. a three-phase power cable, such as may be used in subsea or subterranean environments for electrical power transfer. The invention does not require a power supply at the measurement location, and relies solely on optical fibres (typically present in such cables) to carry light to and from the sensors. Fibre Bragg grating (FBG) based sensors sample the electric field between conductors and convert to a strain on the fibre, as a result of which certain wavelengths of the reflected light are modulated by the instantaneous magnitude of the phase-to-phase voltages to be measured. A sensor module embodying the invention includes a spacer which holds the conductors in a predetermined geometry and locates the FBG sensors between pairs of conductors on which the phase-to-phase voltage measurements are to be performed. At an end of the cable, an interrogation system can extract and interpret the modulation of these wavelengths to infer the measured values of voltage. The invention may be incorporated into a repair splice for retrofitting purposes, and may also incorporate FBG-based current sensors to simultaneously measure current in the conductors.

The invention enables the measurement of the voltage between phases (phase-to-phase voltages) of a multi-phase power cable, e.g. a three-phase power cable, such as may be used in subsea or subterranean environments for electrical power transfer. The invention does not require a power supply at the measurement location, and relies solely on optical fibres (typically present in such cables) to carry light to and from the sensors. Fibre Bragg grating (FBG) based sensors sample the electric field between conductors and convert to a strain on the fibre, as a result of which certain wavelengths of the reflected light are modulated by the instantaneous magnitude of the phase-to-phase voltages to be measured. A sensor module embodying the invention includes a spacer which holds the conductors in a predetermined geometry and locates the FBG sensors between pairs of conductors on which the phase-to-phase voltage measurements are to be performed. At an end of the cable, an interrogation system can extract and interpret the modulation of these wavelengths to infer the measured values of voltage. The invention may be incorporated into a repair splice for retrofitting purposes, and may also incorporate FBG-based current sensors to simultaneously measure current in the conductors.

A sensor for detecting an amount of current flowing in a wire wherein displacement of a sensing mirror is used in an interferometer to enable determination of the amount of current. The sensor includes a magnetostrictive element located within a magnetic field formed by the wire. The sensor also includes a position sensor that detects a size increase of the magnetostrictive element. In addition, the sensor includes an amplifying device that amplifies the size increase of the magnetostrictive element by a predetermined amplification factor to provide an amplified size increase. Further, the sensor includes a displacement device that displaces the sensing mirror by an amount corresponding to the amplified size increase.

An electrical voltage measurement device, comprising at least one microelectromechanical device comprising a semitransparent material element with a variable refractive index n according to an electrical voltage applied to the element, a first electrode connectable to an anode of an electrical voltage source and electrically connected to a first point of the semitransparent material element, a second electrode connectable to a cathode of the electrical voltage source and electrically connected to a second point of the semitransparent material element, wherein the semitransparent material element is configured to receive an electrical voltage from the electrical voltage source through the first electrode and/or the second electrode, causing a variation ?n(V) in the refractive index n proportionally to the electrical voltage; and an optical device.