Study on Accumulated Water and Surface Charge Effect of Capacitive High Voltage DC Bushing

The E-field intensity distribution of the water droplets on the bushing composite insulators is analyzed theoretically. The finite element simulation is used to analyze and calculate the existence of water droplets under the simple electrode system and its influence on the electric field when the contact angle, quantity and spacing change, and the relevant laws are obtained. The water droplets on the surface of silicone rubber distort electric field near it, but have little effect on the farther area. The maximum value of electric field intensity appears at the contact of water air silicone rubber. When the voltage is high enough, corona will occur there first. For different contact angles, the water droplets are similar to a flat disk inserted into the air, and the electric field intensity at the three contacts is quite high. When the air is inserted into water, the electric field at the three contacts is also high. This shows that the intact silicone rubber with the high hydrophobicity can well reduce the surface electric field under the wet conditions, while the silicone rubber that loses hydrophobicity due to the aging, wind erosion and other reasons is more likely to have corona or flash-over under wet conditions. For the different water droplet spacing, the maximum electric field intensity decreases with the increase of spacing. The electric field distortion in the region between water droplets is obvious, and the degree of distortion increases sharply with the decrease of spacing. The area between water droplets is almost unaffected, close to presence of a single water droplet. Moreover, there is polarization peak at the interface of the bushing composite insulator/water drop, which indicates space charge is easy to be generated at the interface, and increasing the temperature will increase the amount of space charge injected at the interface and reduce the amount of space charge at the electrode.