Study on the Effective Ionization Rate of Atmospheric Corona Discharge Plasmas by Considering Humidity

Atmospheric corona discharge plasmas are the most common diversely occurrence in the electric power system. In this paper, four elementary processes occurred in corona discharge are taken into account, including elastic collision, excitation, attachment, and ionization. As one of the most important parameters in corona characteristics analysis, the effective Townsend ionization coefficient is completely calculated by the Boltzmann equation under the consideration of humidity. This paper also derives the electron energy distribution function (EEDF) in water vapor and dry air, respectively. With reference to previous researches and the existing literature, comparisons and validations on ionization and attachment coefficient are conducted. Besides, the effects of humidity, pressure, and temperature on the effective ionization coefficient are also discussed in this paper. It is concluded that humidity can enhance both ionization and attachment. The results show that the ionization coefficient in this paper is well consistent with traditional ones, while there are variations for attachment coefficient. In normal condition, the effective ionization coefficient varies slightly with humidity, but it increases significantly with a decreased pressure or an increased temperature, which cause the change in critical electric field correspondingly.