Inception threshold conditions for positive dc corona in a rod-plane electrode at low atmospheric temperatures

Abstract

The effects of low temperature on the inception threshold conditions of positive dc corona in a rod-plane electrode are investigated. The low-temperature platform, including the refrigeration system, air drying system, and inception threshold measurement system, is used to research the salient inception condition at a wide range of temperatures. This paper also attempts to use the numerical inception model to understand the effects of temperature on ionization coefficient, charge density, primary avalanche length, and radius. In a wide range of temperatures, the inception electric field strength is evaluated through approximate empirical formulas and a numerical model. Experimental results of corona inception are given for temperatures ranging from –80 °C to 40 °C, radii from 0.2 to 1.6 cm, and 20% relative humidity of air. The comparisons between the calculations and experiments of inception voltages under different temperatures are presented. Experimental results are consistent with inception corona voltages being determined by theoretical predictions of photoionization effects producing electron avalanche sizes greater than those produced by net ionization and attachment collisions. It is found that the inception electric field and the inception voltage are pronouncedly influenced by atmospheric temperature.