Examination of ozone emanating from EHV transmission line corona discharges

With the development of EHV transmission systems, research was necessary to measure the amounts of ozone which could potentially emanate from the corona discharges of EHV transmission lines under dry conditions and in the presence of light or heavy rain. The paper reviews experiments performed in two high voltage laboratories. Three cages and seven conductors (solid and stranded, single and bundle arrangements) were used for dry and wet experiments. About 1300 test points were obtained, encompassing a wide range of voltage gradient and corona loss values. Qualitative and quantitative analyses were conducted. Measuring equipment and experience are discussed. Investigations show that the overall average ratio of corona loss to ozone production was about 0.52 kWh/g of 03(235 kWh/lb of 03), based on all of the experiments. Long-term field tests were conducted and an experimental measurement program extending several months before and after energization of a 765-kV line was carried out. All of the laboratory and field examinations confirmed that the ozone levels and production rates within the actual operating voltage gradient and corona loss region were very low, and the ground level ozone concentrations due to EHV transmission line corona were indistinguishable from ambient ozone concentrations.