A Streamer Model for High-Voltage Water Switches

An electrical switch model for high-voltage water switches has been developed which predicts streamer-switching effects that correlate well with water-switch data from Casino over the past four years and with switch data from recent Aurora/AMP experiments. Preclosure "rounding" and postclosure resistive damping of pulseforming line voltage waveforms are explained in terms of spatially extensive capacitive-coupling of the conducting streamers as they propagate across the gap and in terms of time-dependent streamer resistance and inductance. The arc resistance of the Casino water switch and of a gas switch under test on Casino was determined by computer fit to be 0.5 ± 0.1 Ω and 0.3 ± 0.06 Ω, respectively, during the time of peak current in the power pulse. Energy lost in the water switch during the first pulse is 18 percent of that stored in the pulseforming line while similar energy lost in the gas switch is 11 percent. The model is described, computer transient analyses are compared with observed water and gas switch data, and the results-switch resistance, inductance, and energy loss during the primary power pulse-are presented.