Influence of air pressure and humidity on positive direct current corona discharge performances of the conductor in a corona cage

Abstract

SUMMARY With the implementation of West-to-East Power Transmission Project in China, transmission lines will inevitably pass through high altitude regions with complex atmospheric conditions. The effects of such atmospheric parameters as pressure and humidity on the corona discharge performances of conductors are complicated. Especially as to the effect of air humidity on corona inception voltage, researchers have not reached an agreement. Therefore, by adjusting air pressure and air humidity in a corona cage, the positive direct current corona discharge performances of a smooth steel tube are tested. Results indicate that corona inception voltage increases significantly with the increase of air pressure, and the calculated results by discharge model are in accordance with measured results. Yet, with the increase of absolute humidity, corona inception voltage increases slowly. Under high humidity condition, corona inception voltage decreases because of the condensation on conductor surface, which distorts the surface electric field. In view of the condensation, the calculating model is improved, whose calculated results are in line with measured results. Moreover, it is found that inception discharge is easier to turn into glow discharge under low pressure and low humidity condition. The average pulse amplitude decreases with the increase of humidity, but with the increase of pressure, it decreases first and then increases. The rising time of the discharge pulse presents increasing trend with the increase of both air pressure and air humidity. All the test results are analyzed from microscopic mechanism. Copyright © 2013 John Wiley & Sons, Ltd.