A Summary of Radio Interference Studies Applied to EHV Lines

The source and nature of corona discharges on EHV (extra-high-voltage) lines, and the effect on RI (radio interference) meters, is reviewed. A relationship between conductor diameter and operating gradient is given. Propagation experiments and mode analyses of radio noise, using artificial sources at the Coldwater test line, are described. Results of long-time RI recordings at the 500-kv test line, and close to a 230-kv circuit, are compared.