Effect of Surface Charges on Flashover Voltage - An Examination Considering Charge Decay Rates

The effect of the position and amount of surface charges on cylindrical polytetrafluoroethylene (PTFE) insulators with different surface conductivities is studied. The surface potential decay property with time is investigated subjected to different electric fields. A simulation model for charge transport is established. The results show that the surface potential decays exponentially after surface treatment. The decay rate of surface charges increases with the surface conductivity. At t = 180 seconds, the decay rates of surface potentials for different surface conductivity are 2%, 42%, 60% and 84%, respectively. For samples with the same surface conductivity, the decay rates of surface potentials under different initial values are about 57%, and the decay rates at different accumulated locations are about 62%. It is demonstrated that the surface charge decay rate has little difference when initial charges with different amount and positions are introduced. However, the dissipation of surface charges can be promoted by applying a voltage of the same polarity. When the surface conductivity is increased to 5.1 × 10 ^-16 S, the potential decay rate under the applied voltage increases to 76%. Furthermore, the flashover voltage decreases with the increase of surface conductivity. As a result, the effect of homopolar surface charges on the flashover voltage is reduced.