Corona Discharge Analysis of a 400kV Overhead Line at Its Tower Windows and Line Mid-Span Under Fog Condition

One of the main factors on the high voltage overhead transmission line corona performance is due to the electric field generated at the surface of the phase conductors. Since, an electric field is established in the air surrounding the live conductors, the free ions and electrons in the air will experience a force, then this force will accelerate the ions and free electrons and cause the ionization of the air molecule and corona discharge will be produced. So, determination or accurate estimates of this electric field will be needed especially during step design of the extra and ultra-high voltage overhead transmission line. In these transmission lines to achieve the electric field amplitude under corona inception does not usually give optimum design view point of economic and also in the case of designed and operated overhead transmission line, the design parameters may be changed and maximum electric field augments. In this paper, corona inception of an old overhead 400kV transmission line in Iran power network will be studied, since recently in autumn and winter seasons, especially under fog conditions due to climate change, the outage of this line is increased and it became as a center attention of local operation office. So the electric field distribution precise analysis and evaluating the innovative methods is needed to reduce its maximum electric field until it reaches under the inception of corona discharge. In this regard the finite element method based analysis tool, COMSOL software, has been used to determine the electric field distribution in high voltage transmission line by considering the tower structure and all equipment implemented in a suspension tower one. Also it is carried out to reduce maximum generated electric field of this available transmission line by the best solution and finally this electric field reduction can remove unwanted line outage.