Broad band pulse detection studies of partial discharges in presence of solid dielectrics in -CF6N2 mixtures

Abstract

Experiments were conducted to detect partial-discharge (PD) pulses in the presence of solid dielectrics (PTFE and glass-filled epoxy) as well as breakdown pulses in SF6, N2, and SF6 -N2 mixtures under uniform field conditions using a broadband detection system. The effects of circuit parameters, overvoltages, gas pressure, and the distance between electrodes on pulse shapes were studied for various proportions of SF6 in -SF6N2 mixtures. The observed PD pulses are similar to breakdown pulses for longer electrode gaps &(gt;0.3 cm). In the case of surface discharges the pulses are oscillatory in nature and inconsistent in shape and magnitude. The effect of saturation on the increase in breakdown voltage of -SF6N2 mixtures with increase in percentage of SF6 (i.e. synergism) is also observed in the presence of the solid dielectric. This synergistic effect is reflected in corresponding observed PD pulse shapes