Analyzing of AC Corona Discharge Parameters of Atmospheric Air

Abstract

Corona on transmission line conductors is a significant source of electromagnetic interference and corona loss. In order to analyze variable atmospheric condition on corona inception voltage gradient of bundle conductors a calculation model was established. The voltage gradient around stranded conductors for calculating corona inception voltage gradient is required. For the high voltage transmission lines, it is necessary to know the electric field in vicinity of the conductor's surface to determine the conditions for corona inception. The conditions under which corona discharge occurs for any arrangement of conductors are an important design consideration since corona can limit the performance of any given configuration of transmission line conductors. The AC corona inception voltage gradient criterion should involve the line characteristics, i.e., arrangement and size of conductors as well as atmospheric condition of the air in which the conductor is immersed. The numerical calculation method, as well as empirical equations, combined with gas discharge theory is adopted to investigate corona inception voltage gradient. The electrical field enhancement at the tip of each strand is about 14% higher than the electrical field for a cylindrical conductor of the same overall diameter. According to self-sustained corona discharge criterion in a severe non-uniform electric field, variations of pressure, temperature and humidity on corona inception voltage gradient of bundle conductors are analyzed. Increased voltages in 400kV electric power network of Bosnia and Herzegovina causes increase the value of voltage gradient and higher power losses due to AC corona. Therefore, it is important to determine the value of the voltage gradient in vicinity of conductor's surface as well as corona inception voltage gradient to accurate determined power losses due to AC corona.