Insulation performance of rigid polyurethane foam and its application in station post insulator

For high-voltage station post insulators, the common solution of internal insulation is solid core or hollow insulation system filled with SF
₆
or N
₂
gas. As for the former, the heavy structure is a trouble for installation; for the latter, possible gas leakage may endanger the insulation. Thus, it is necessary to provide a reliable and economical insulating material to solve above-mentioned problems. This paper focuses on the application of rigid polyurethane foam (PUF) to fill the hollow space in the composite post insulator. The micro-structure of PUFs was firstly observed by SEM. Thereafter, their dielectric strengths were examined under different temperature and humidity conditions. In addition, the V-t characteristics were investigated to verify the long-term voltage endurance. Finally, the whole post insulators filled with PUF were tested. The results show that the PUF has much higher dielectric strength than air. The breakdown electric-field increased with the temperature increasing, and the high humidity has negligible effect on its insulation performance. The long-term stability of PUFs is also confirmed from this study. Thus, PUF can be used as a reliable solution for the internal insulation of station post insulators.