Application of streamer criteria for calculations of flashover voltages of gaseous insulation with solid dielectric barrier

Streamer inception and propagation criteria are used for evaluations of ac breakdown voltages of sphere-sphere gaps employing a dielectric barrier in dry air. For such an arrangement, an optimal location of the barrier is expected to exist providing maximum value of the breakdown voltage. To reproduce the barrier effect, different calculation approaches are considered including models based on undisturbed electrostatic field distributions and models accounting for charging of the barrier due to a pre-breakdown streamer. The breakdown voltages calculated for different positions of the barrier in the inter-electrode gap are examined and are compared with the results of themeasurements. It is revealed that charges on barrier surfaces have to be considered when using the streamer criterion for a quantitative prediction of the barrier effect