A method for detecting partial discharges in the insulation of an electric heavy-current cable

摘要

Method for detecting partial discharge in an insulation of a wire shielded electric power cable comprising an electric conductor, an insulation and a wire shielding layer with by the steps: providing a detecting coil around said wire shielded electric power cable, applying a predetermined line voltage to the wire shielded cable, obtaining a first frequency spectrum of external noise by use of a detecting coil, a detecting impedance connected to the terminals of the detecting coil, and a partial discharge detecting apparatus connected to the detecting impedance, supplying a calibration pulse to the high voltage conductor, obtaining a second frequency spectrum of the calibration pulse by use of the detecting coil, the detecting impedance and the partial discharge detecting apparatus, and comparing the first and second frequency spectrum with each other above 7 MHz at around 11 MHz to thereby detect said partial discharge in accordance with the so measured electromagnetic coupling between said detecting coil and shielding wires of said wire shielded electric power cable. IMAGE