Initiation of Internal Discharged in a Liquid-Nitrogen-Filled Cavity

Discharge initiation phenomena in a liquid-nitrogen-filled cavity were investigated using "ac impulse" i.e., the initial rise of a 50 Hz voltage wareform. It was found that the discharge magnitude in the beginning half cycle of the voltage was either greater, equal, or smaller than that observed in the next half cycle. This phenomenon is discussed in terms of discharge processes and the quantity of discharge-formed bubbles. Overvoltage characteristics of the discharge magnitude were found in both liquid and gaseous nitrogen filled cavities. A semi-empirical formula has been derived which corrlates the discharge magnitude and overvoltage. It was also shown that liquid nitrogen discharges are accompanied by luminescence.