Effect of pollution severity class and service year on corona characteristics and electromagnetic environment degradation of aged conductors

•Using long-term operated transmission lines from different pollution severity classes.•Influence of conductor surface condition on corona discharge of transmission line.•Effect of service year and pollution severity class on PC, AN and RI of conductors.

Corona discharge and electromagnetic environment on AC long-term operated conductors are important issues for extra-high-voltage transmission lines. To investigate the relation between conductor age and electromagnetic environment, including audible noise and radio noise, several groups of long-term operated conductors in China are selected for corona cage experiment. According to corona tests, corona discharge becomes more serious as the applied voltage improves. Difference of electromagnetic environment between conductors of different operated year increases. Corona discharge and electromagnetic noise become more serious as the service year lengthens. When the operated years are close, the general environment is important in electromagnetic environment degradation.