Studies on modeling corona attenuation of dynamic overvoltages

An experimental and theoretical study is presented on the corona characteristics of conductor bundles under dynamic overvoltages. Measurements have been made in the outdoor test cages of Institut de Recherche d´Hydro-Quebec on two bundles, under conditions of fair weather and heavy rain, for steady 60 Hz voltages as well as dynamic overvoltages. Based on the data on corona currents and losses obtained, a nonlinear resistance model of corona is proposed for attenuation studies. The Suliciu model for corona, originally developed for unipolar impulses, has been adapted for dynamic overvoltages. Both these corona models are used to study the influence of corona on the dynamic overvoltages developed during line energization and load shedding of a single-phase line. Among other findings, it is shown that the corona phenomenon stabilizes after the first half-cycle of the dynamic overvoltage. The corona losses of conductor bundles under fair weather conditions increase rapidly with the conductor surface voltage gradient; they approach losses under heavy rain at higher gradients