Internal Temperature Detections of Contaminated Silicone Rubber Under Discharge Conditions Based on Fiber Bragg Gratings

Composite insulators are widely used in power grids at home and abroad. The anti-pollution flashover performance, hydrophobicity and hydrophobic migration, and pollution flashover mechanism of composite insulators have been the focus of international attention. Temperature is one of the important parameters to describe the flashover of composite insulators. In this paper, the internal temperatures of a composite insulation sample were detected based on FBGs (fiber Bragg gratings). The sample was layered and made of one layer of silicone rubber 3 mm in thickness and one layer of epoxy-GFRP (Glass Fiber Reinforced Plastics) similar to 220 kV composite insulators. Three gratings were embedded in the interface of the two layers between long and short electrodes on the surface of the sample. Temperature calibration tests were carried out on the gratings in the sample. Then, discharges tests were done on the sample with embedded FBGs. Internal temperatures as well as leakage currents were measured, and the arcs process of the discharges on the sample was photographed. The test conditions are as follows: the output voltage was increased by approximately 0.5 kV/s; the equivalent salt deposit density (ESDD) was about 0.5 mg/cm2 and the non-soluble deposit density (NSDD) was about 1.2 mg/cm2.The results show that the internal FBGs could sense the flashover on the surface of the sample. An interface temperature rise caused by the discharges is within 11 °Cin this paper. There is a time delay of 1.4 s from the leakage current arise to the temperature rise during the discharges. The arcs always develops from the small electrode to the large electrode on the surface of the sample, the rise process of the internal temperature at the interface under the middle surface position of the two electrodes is significantly different from that near the small electrode, the arcs starting electrode, while similar to that near the large electrode, the flashover electrode.