Study on the interface partial discharge between silicone rubber and fiber reinforced plastic in composite insulators

The internal macroscopic interface, which is between fiber reinforced plastic (FRP) and silicone rubber, is the weak point in the whole composite insulation system, in general. Moisture ingress may lead to interfacial adhesion loss and even cause a significant decline of insulation properties. It should be noted that, it is lack of the detection method for interface electrical properties. In this study, an electrode system is designed and manufactured to measure the interface partial discharge (PD). The electrodes are embedded into the interface during the curing process. As we know, when the composite insulators encounter liquids, the liquids may permeate into the silicone rubber housing via diffusion process and reach the interface between the silicone rubber and FRP, which may cause the damage to the interface and also the change of PD properties under ac voltages. In our study, the PD properties in the interface before and after liquids permeation were measured by a PD measurement system. The liquids we chose in this study were three kinds, including deionized water, NaCl solution and HNO3 solution, since composite insulators encountered such kinds of liquids in practice. Since the permeation time for liquids was the key point, different values of PD were gained after several different days' permeation, which may reflect the deterioration process of the interface. Our PD research, together with the past test results about interface resistivity, could provide an in-depth understanding of the interface performance in composite insulators.