Study on the Degradation of FRP Rod of Composite Insulator under Electrical Stress and Salt Fog

Decay-like fracture of the composite insulators has become a major threat to the operation of high voltage transmission lines. Nevertheless, the mechanism of decay-like degradation is still not clear enough. In this paper, electrical stress as well as salt fog is applied to a FRP core rod partly covered by silicone rubber sheath to simulate the decay-like degradation process. At the end of the experiment, the FRP core rod is found to be eroded seriously by surface discharge, and carbonization appears in local position. According to SEM observation, the epoxy resin is melt and decomposed. Besides, air bubbles and holes can be witnessed on the melted epoxy resin matrix. The result of FTIR exhibits that the content of methyl group, aromatic group and alicyclic group gets lower compared to the intact position of FRP core rod, while the content of hydroxyl group increases. TGA result further indicates that the content of epoxy resin reduces, which is consistent with the FTIR measurement. This work provides a possible method for the study of the mechanism of decay-like degradation.