Seasonal Variation of Fair-Weather Radio Noise

One year of fair-weather radio noise (RI) data from an EHV line was analyzed. Two types of variation were found: long- term over several months and short-term over several days. Summer RI readings were higher than winter readings by 12 dB and lasted longer. Based on these results, a procedure for predicting average monthly RI levels is outlined. Short-term variations of fair-weather RI level were analyzed statistically using the washing effect of rain on the conductor surface as an explanation of the RI variation. Results yielded a favorable inference for the statistical model.