Emissivity of Weathered Conductors After Service in Rural and Industrial Environments

It has been recognized for many years that well-weathered conductors, after being energized for a period of time, have a dark surface resulting in an emissivity sometimes as high as 0.98, whereas a new conductor has an emissivity of approximately 0.23. The length of time needed to develop a high emissivity with the consequent higher current capability is of interest. Samples from various parts of the United States, with the time of service been collected and the emissivity determined. A conductor energized at 500 kv for 1 year at Leadville, Colo., at an altitude of 10,500 feet above sea level, had the same emissivity, 0.23, as a new conductor.