Method for detecting partial discharges in an insulator of an electrical conductor

A method for detecting partial discharges in an insulator of an electrical conductor of a medium-voltage or high-voltage electrical device, the electrical conductor being subjected to an alternating voltage,

• the method comprising the steps of:
• (i) successively acquiring a set of samples of an electrical signal representative of a partial discharge in the insulator of the electrical conductor,
• (ii) for each sample in the set of samples, determining the value of the phase of the alternating voltage,
• (iii) establishing a two-dimensional matrix of elements, wherein:
• a first dimension of the two-dimensional matrix corresponds to a set of ranges of values of the phase of the alternating voltage,
• a second dimension of the two-dimensional matrix corresponds to a set of amplitude ranges of the samples of the set of samples of the electrical signal, and
• the value of each element of the two-dimensional matrix is equal to the number of samples within the value range of the phase of the alternating voltage associated with said element of the two-dimensional matrix and comprised within the amplitude range of the electrical signal associated with said element of the two-dimensional matrix,
• (iv) determining in the established two-dimensional matrix a portion corresponding to electrical noise, known as the noisy zone, according to a condition based on at least:
• a first statistical quantity representative of a number of values associated with an amplitude range of the electrical signal,
• a second statistical quantity representative of a variability of the number of values associated with said amplitude range of the electrical signal,
• (v) for each element of the two-dimensional matrix forming part of said noisy zone, replacing the value of said element by the result of a mathematical function of at least:
• a first element of the two-dimensional matrix located outside the noisy zone, referred to as the first reference element, the first reference element being associated with:
• the same value range of the phase of the electrical voltage as said element, and associated with
• an amplitude range below the amplitude range of said element, and
• a second element of the two-dimensional matrix located outside the noisy zone, referred to as the second reference element, the second reference element being associated with:
• the same value range of the phase of the electrical voltage as said element, and associated with
• an amplitude range above the amplitude range of said element,
• in order to establish a two-dimensional corrected matrix of elements,
• (vi) detecting the presence of partial discharges or the absence of partial discharges in the insulator from the corrected matrix established.