Investigation on AC Dielectric and Breakdown Properties of Fluorinert Liquid-Impregnated Insulation Paper

With the expanding scale of UHV transmission projects, the lack of high-performance insulation combinations has threatened the safe operation of the power system. Phase-change material with suitable thermal stability and insulation characteristics is gradually being applied to high-voltage power electronic devices as refrigerants. Oil-paper insulation technology has been extensively studied, but no systematic compatibility tests are focusing on refrigerants and insulation materials. In this paper, Perfluoro-compound (FC-72) and Perfluoroheptano (EC74) were selected to study the compatibility with insulating paper at room temperature. By carrying out power-frequency breakdown voltage test, dielectric loss characteristics test, and SEM detection, electrical characteristic curves at different stages and temperatures, surface and profile microscopy images of two electronic fluoride liquid-impregnated insulating paper were obtained. Whether from the macro or micro perspectives, it can be proved that compatibility of FC-72 with insulating paper were significantly better than FC-74, and it also helps to improve the electrical resistance and aging resistance of insulating paper, which means FC-72 can be used as an alternative to excellent insulating oil for transformers.