Abstract: The invention relates to a method for inputting an information signal into a power cable which is connected to a voltage supply and which includes at least one or more conductors, a dielectric provided around the conductors and a conductive earth sheath arranged wholly or partially around the dielectric, the method incluging inputting a pulse-like information signal at a first position via the earth sheath in order to produce a corresponding pulse-like information signal which is propagated to a second position in the dielectric of the power cable.

Abstract: A method and apparatus for detecting partial discharges in cables and accessories. An electrical interruption is created in, for example, the sheath conductor of a cable, and the voltage of high frequency signal components, created by a partial discharge, is measured across the interruption. The interruption is short-circuited to allow low frequency signals to pass across the interruption, thus preventing low frequency signals from being measured. This is useful because the signal/noise ratio of the frequency range measured according to this invention is more favourable. Also, in order to properly and accurately measure a partial discharge, it is important to relate measurements to the main supply voltage of the cable. The present invention also provides a method wherein prior to display the signal is combined with a signal representing the main supply voltage.

Abstract: The invention relates to a method for detecting partial discharges occurring in a cable, wherein the cable has an earth screen with a helical structure, comprising the following steps of: arranging at least one detection coil round the cable for detecting electromagnetic pulses travelling along the cable; applying a potential difference between the core and the earth shield of the cable; and analyzing pulses generated by possible partial discharges in the at least one detection coil in order to determine the location and quality of the partial discharge having caused the pulse, wherein the detection coil is adapted to process signals with a frequency higher than 100 MHz. It has been found that with coils comprising only such a limited number of turns the signal detected by the coil is a much better representation of the form of the electromagnetic pulse travelling along the cable.