Calculation of the corona onset voltage gradient under variable atmospheric correction factors

Corona phenomena on conductors are of importance for high voltage transmission lines. In this paper a calculation of the corona onset voltage gradient of AC conductors has been performed for taking into account the effects of atmospheric conditions. Corona characteristic on overhead transmission lines (OHTL) are influenced by a several factors. The conductor surface roughness and atmospheric conditions have a direct influence on the corona onset voltage gradient. Atmospheric conditions have the largest influence on the value of the air density. The air density is function of the ambient temperature and pressure. Ambient temperature at any given location is subject to daily and seasonal variable. The transmission line crossing a high humidity area and thus humidity should be taken into account in evaluating of the corona onset voltage gradient. Increased voltages in the 400 kV electric power network of Bosnia and Herzegovina are increasing the value of the voltage gradient and higher power losses due to AC corona. Therefore, it is important to determine the value of the voltage gradient on conductor surface as well as corona onset voltage gradient to accurate determined power losses due to AC corona.