Patent ID: 8447540

Claim:
A method for detecting, identifying and locating partial discharges occurring in a discharge site along an electric apparatus, wherein said electric apparatus is a cable having a plurality of accessories, comprising the following steps: identifying a plurality of detection stations along the apparatus to be evaluated, wherein said detection stations are spaced apart and positioned along substantially the whole length of the apparatus, wherein detection stations are positioned at a plurality of accessories of the cable; detecting (1) analogue electrical signals captured by a sensor operatively coupled to the apparatus in a detection station and generating a set of corresponding digital signals representative of the wave forms of said analogue signals; attributing (2) to each detected signal a value of a phase parameter representative of the phase of the voltage applied to the electric apparatus at the instant of the detection of the signal; deriving (3), for each of said digital signals, at least one shape parameter correlated to the wave form of that signal and at least one amplitude parameter correlated to the amplitude of that signal; separating (4) the set of said detected digital signals into sub-sets, so that the digital signals of each sub-set have similar values of the shape parameter; identifying (5) the sub-sets of signals relating to partial discharges and cataloguing them, as a function of statistical evaluations based on the values of the parameters of amplitude and phase for the signals of each sub-set evaluated individually; repeating the previous steps, for each detection station of said plurality of detection stations positioned along the apparatus, until said steps have been executed in all the detection stations, wherein said sensor is moved progressively along the apparatus, from one detection station to the subsequent detection station; correlating (7) the sub-sets of signals catalogued similarly and detected in said different detection stations positioned at different accessories of the cable; selecting (8) a sub-set within a group of correlated sub-sets, based on the values of the shape and amplitude parameters for the signals of the different sub-sets of said group, and locating (9) the partial discharges related to said signals at the detection station of the selected sub-set, wherein, in the selection step (8), the sub-set is selected as a location of the partial discharge source whose signals have maximum values of the amplitude parameter and of the shape parameter correlated to the frequency content of the signals and minimum values of the shape parameter correlated to the time duration of the signal, relative to the other sub-sets of the group of correlated sub-sets, corresponding to the other detection stations positioned at different accessories of the cable.