Impact of Water Permeation on the Dielectric Response of HTV Silicone Rubber

As the material for shed and sheath of composite insulators, HTV silicone rubber faces multiple stresses in the serving environment, in which water permeation may lead to degradation and harm the cores. This research studied in the dielectric response of HTV silicone rubber samples which have been immersed into deionized water, and analyzed the test results with Dissado-Hill loss peak model and QDC model. Both real and imaginary parts of the dielectric response increased after immersed for 400h. The fitting results showed that the QDC phenomenon was more obvious after long time immersion. Water promoted the number of charges which participated in the hopping process, and offered path for the hopping process in QDC. Meanwhile, water invading made the interfaces loose and led to disorder of the structure. These results prove that water permeation is highly likely to be the reason of chalking on the shed and sheath of composite insulators.