Effect of electrical stress on glass fiber reinforced polymer used in high voltage composite insulator under wet environment

The effect of electrical stress on glass fiber reinforced polymer under wet condition has been investigated in the present study. A specially designed and fabricated test setup was used through which the current passing through the GFRP rod during the test was recorded. Based on the changes in morphology of GFRP rod surface and development trend of current, the degradation process of GFRP rod caused by electrical stress under wet condition was divided into four consecutive stages, namely degradation inception stage, hydrolysis stage, carbonization stage and breakdown stage. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray Photoelectron Spectroscopy (XPS) analyses were employed to provide the physical and chemical properties of GFRP at different stages. The results showed that the degradation process of GFRP caused by electrical stress under wet condition progressively developed in the form of degraded channel, in which the epoxy resin matrix deteriorated significantly. The occurrences of hydrolysis, oxidation, pyrolysis and carbonization of epoxy resin matrix could be observed sequentially in the degradation process of GFRP during the test. With the development of the degradation process of GFRP, the content of epoxy resin matrix continued to decrease and the relative content of highly oxidized carbons (C-O, C=O and O-C=O) in epoxy resin matrix on GFRP surface increased before the carbonization process and then decreased in the carbonization process. The present study is helpful for better understanding of the electrical performance of GFRP used in high voltage composite insulator as well as in other electrical applications.