Partial discharges in dielectric liquids

In this paper, we have investigated the behavior of dielectric properties (partial discharges) of liquids of different natures (silicon oil, aromatic liquid). Partial discharges measurements have been done over the voltage range (0-25 kVpp). Two types of devices have been analyzed. The first one consists of a ceramic covered by liquid, the second one of a needle-plane system embedded in liquid. The origin of partial discharges for the both devices is discussed. A mixture of corona effect and discharge in micro voids appear for the ceramic based system whereas only the corona effect was identified for the second one. Results are then discussed in correlation with potential applications in power electronic components where rubber and gel are used for IGBT module.