Impact of Daily Variations of Atmospheric Conditions on the AC Corona Onset Electric Field
The electric power network in Bosnia and Herzegovina on the 400 kV voltage level built up in the 70’s of the last century, has an important role for the electric energy exchange. Its parts are more than 40 years old. The paper investigates the impact of daily variations of the atmospheric conditions on the AC corona onset electric field. The AC corona onset electric field on overhead transmission lines is affected by a several factors. Besides the conductor dimensions, the atmospheric conditions have the largest impact on the value of the relative air density as well as the surface conductor roughness. The relative air density is a function of the ambient temperature and pressure. Ambient temperature at any given location is subject to daily and seasonal variations. The ambient pressure is not subject to large daily variations. The sag of the overhead transmission lines increases by an increase of the conductor temperature due to the electric load and specific atmospheric conditions. Increased voltages increase the value of the electric field and can presents risks for the exposure of human beings. Also, high voltages in the network cause high power losses due to the AC corona.