Minimum steady corona inception voltage calculation method under rain condition

Abstract

As the most common precipitation form, rain-lead corona problems are inevitably faced by designers of transmission lines. Through long-term observations of corona inception process under rain conditions by ultraviolet camera, a definition of minimum steady corona inception voltage is presented, which is more useful for practical application. To predict the minimum steady corona inception voltage, water droplet deformation model of smooth conductor is promoted based on the principle of minimising energy in this publication, which takes the influence of electric field force into consideration. Critical breakdown voltage and corresponding critical geometric dimensions of specific water droplet are calculated through the deformation model. The accuracy of the presented deformation model is proved to be >95%, by verification tests performed in a corona cage. Corona discharge model presented in the previous work is adopted to predict the water droplet corona inception voltage of given geometric dimensions. Finally, through the calculation results of both models, the defined minimum steady corona inception voltage of smooth conductor is calculated when there exist rain droplets on conductor lower surface. Also, the calculation error of minimum steady corona inception voltage is ∼8.0% when compared with the validation experiments.