Effect of pressure and supply frequency on the mean free path and mean energy of corona-generated electrons in air

• Corona discharges create unwanted effects in power systems that must be addressed. • The mean electron free path and mean energy are key indicators of corona activity. • A simple method to calculate the mean electron free path and mean energy is proposed. • This method is applied to different atmospheric pressures and supply frequencies. • We present experimental data at several atmospheric pressures and supply frequencies. Corona discharges have many industrial applications, but in high-voltage systems, they often create unwanted effects that need to be addressed. Therefore, design engineers need simple tools to control their effects and, when they do occur, to determine the potential impact. Since the mean free path and mean energy of corona-generated electrons are key indicators of plasma characteristics and the efficiency of various processes occurring within the discharge, these parameters provide important information about the intensity and performance of the discharge. In this work, an easy-to-apply method is developed to determine the mean free path and mean energy of corona-generated electrons once the local electric field is known, which can be determined from finite element method simulations. The mean electron free path and mean electron energy can then be determined from published experimental data relating the total electron collision cross sections with air molecules to the mean electron energy and the mean electron energy to the reduced electric field. The method presented here is applied to experimental data obtained at different supply frequencies and different pressures typical of aircraft systems, which, due to the imperative need for electrification, are exposed to a higher risk of discharges due to the higher operating voltages, higher supply frequencies, and low pressure environment.