PARTIAL DISCHARGE DISTRIBUTIONS IN LIQUID DIELECTRICS

Different dielectric fluids used in HV electrical components were subjected to ac stresses and the partial discharges (PD) spectra produced under non-uniform and uniform field conditions were recorded with the help of an electrical detector and a multichannel analyzer (MCA) as a function of applied stress. The analysis of the collected data confirms that PD activity in a liquid is a random phenomenon as well as a breakdown process. The presence of PD may be related with the presence in the liquid of bubbles near the electrode interface and with a low density region (vapor phase), that is the first step in the breakdown development. This confirms that PD occur only in a gas and not in a solid or liquid. In this paper, which is a part of an ongoing research project it is shown that the use of a MCA may be an helpful tool in PD measurements and analysis and this allows to show how the partial discharge inception voltage (PDIV) significantly change according to the adopted inception criteria.