Corona and RI Caused by Particles on or Near EHV Conductors: II - Foul Weather

This study was made to identify and photograph the foul-weather coronas occurring on a high-voltage transmission-line conductor and to establish their radio-noise importance. On the most tested 230-kV line, snow impingement plumes caused radio interference (RI) to 90 times, and water drop spray plumes to 75 times, that of the base fair-weather noise level. Foul-weather RI caused by snow, rain, fog, ice, and condensate associated with the conductor overrode RI generated on insulators, accessories, hardware, and weathered conductor protrusions. H/sub 2/0 particles in different forms were present in the conductor environment for one-fifth the yearly time. The conductor surface gradient, the rate of decay outward from the conductor, the total conductor surface area, H/sub 2/0 particle size and formation, and air velocity over the conductor are important to both particle attachment to the conductor and to the severity and form of corona. This corona occurs as plumes, impingement plumes, spray plumes, glows, and microsparks. Confirming laboratory tests were made at 230 and 345 kV. Confirming observations were made on 345-and 500-kV lines. Corona losses were caused by impingement plumes during snowstorms and principally by spray plumes in rain.