Understanding the water droplet initiated discharges on gamma irradiated silicone rubber insulation

摘要

Corona inception voltage (CIV) due to water droplet on gamma-irradiated silicone rubber indicates that its value reduces with increase of conductivity and with number of droplet in the electrode gap along the axis of the electrode. Increase in dosage of gamma irradiation to silicone rubber reduces the CIV. The UHF signal generated during corona inception due to water droplet has frequency bandwidth in the range of 0.3-1.2 GHz. The discharges occur in the phase range of 30 degrees-130 degrees in the positive half cycle and about 210 degrees-270 degrees in the negative half cycle. The water droplet shape gets altered on application of voltage. Surface charge accumulation studies indicate characteristic change with gamma irradiated specimen. In the presence of water droplet, the charge decay occurs rapidly with a single droplet and with three droplets. Thermal analysis of gamma radiation dosed samples reveals the destabilization of silicone material and the formation of higher order cyclic siloxane oligomers and oxygenated organics, which are expected to act as potential charge trapping sites. POLYM. ENG. SCI., 59:182-191, 2019. (c) 2018 Society of Plastics Engineers