Analysis and measurement of radio-frequency interference due to the corona from 500 kV transmission lines

This paper presents a method to consider the radio-frequency interference (RI) induced by corona from an EHV transmission line system. There are two major types of RI in our consideration. The first is the RI radiated from the transmission line at typical conditions. The other is the relative RI due to the change of environmental factors such as air density, ground conductivity and the determined frequency. The overall RI is described by the sum of these two RIs. The modeling RI for n-phase transmission lines is described, especially, for the three-phase 500 kV system. The experimental data on RF signals were obtained from a survey of 24 sites along the 500 kV power lines along an 800 km distance. The RF signals from the power lines in both vertical line and horizontal line systems were investigated in terms of the spectral levels of frequencies from 0.5 to 100 MHz at a distance away from the power lines. The results are relatively well matched to our theoretical model, and hence, may use the model to prevent this RF interference.