Standard Evolution of Partial Discharge Detection in Dielectric Liquids

Partial Discharges (PD) detection in HV components has shown to be a very powerful diagnostic tool. Anyway, also the acquisition of the same signals in simple insulations, like the dielectric liquids, may give additional information for maintenance of HV components in which they are employed, as in the case of liquid insulated transformers. Among the standardized electrical tests suggested for the insulating liquids, the breakdown voltage (IEC 60156) and partial discharges determination (IEC 61294TR) at power frequency are not basic material properties but test procedures intended to indicate the presence of contaminants such as water and solid suspended matter and the advisability of carrying out drying and filtration treatment. Nevertheless, the PD detection method for insulating liquids actually standardized is based on superseded circuitry and is only addressed to measure the PD Inception Voltages (PDIV). The present paper shows the state of art in PD measurements in dielectric liquids to be taken into account when revising the actual IEC 61294TR or preparing new international Standards (ASTM).