Evaluation of electric field distribution on a 400 kV composite insulator under various service conditions

In this paper, we evaluated electric field distribution along core, weather sheds surface and corona ring of a 400 kV composite insulator under different surface conditions (dry and clean, polluted, in presence of water droplets). Electric field was found higher nearer triple junction point (air-end fittings-housing material). We noticed that the presence of water droplets and pollution layer distributed on weather sheds enhance the local electric field but it doesn't really affect the electric field distribution inside the FRP core. Moreover, for the polluted case, the effect of pollution layer conductivity is insignificant contrary to its thickness. For thicker pollution layer, the maximum electric field point moves from the triple junction point. Finally, corona ring is necessary for a 400 kV insulator for both ends (HV and ground) and its behavior is affected under polluted and wetted conditions. Corona ring parameters (corona ring diameter, corona ring tube diameter and corona ring height) were kept constant through the whole study.