Electric Field Grading Using Thin Film Nonohmic Zinc Oxide

The transient response of thin film non Ohmic zinc oxide is studied to determine if the material would be able to keep up with power system abnormalities such as switching surges and lightning strokes. The transient model is based on a lumped parameter model of the distributed problem. It is found that the maximum electric field seen by the insulator was a function of film thickness, ground capacitance, and the characteristic time of the drive. It does not appear to be affected strongly by the internal capacitance of the film. The switching time of the film, being on the order of a nanosecond, does not appear to have an effect on transients of the time scale of lightning or line switching, indicating satisfactory film performance for sufficient thicknesses.