Effect of High Altitude on High Voltage AC Transmission Line Corona Phenomena

This paper summarizes the results of a research effort conducted by Bonneville Power Administration (BPA) to determine the effect of altitude on corona phenomena from high voltage transmission lines. A computer-controlled, reliable, unattended test station was installed at an altitude of 1935 m on a double-circuit 500-kV line near Basin, Montana, to continuously monitor audible noise (AN), radio noise (RI), and television interference (TVI). To obtain comparative data at a lower elevation, another test station was installed on a 500-kV line of similar design near Stayton, Oregon, at an altitude of 277 m. Comparison of the high altitude data with the lower elevation data and with predictions demonstrated that the correction factor of 1 dB/300 m developed in the 1950´s and 1960´s for radio noise is still valid and is also applicable for AN, TVI and, possibly, corona losses.