METHOD OF DETECTING PARTIAL DISCHARGE IN A GAS INSULATED HIGH VOLTAGE ELECTRICAL SUBSTATION

Method of detecting partial discharge in a gas insulated electrical substation, in which: -a frequency spectrum of the signals detected by a UHF sensor internal to said substation and a frequency spectrum of the signals detected by a UHF sensor external to said substation are measured (1, 2), -an average and a variance of the frequency spectrum of the signals detected by the internal sensor are calculated (3), -said average and/or said variance are compared (4) respectively with a threshold of average and/or of variance so that, if said average and/or variance is greater than or equal to the threshold of average and/or of variance: -a density of the frequency spectrum of the signal-to-noise ratio formed (5) from the spectra of the signals detected by the internal and external sensors is calculated (6), and -an alarm signal (A) is generated if said density is greater than or equal to a density threshold.