Continuous Recording of Outdoor Insulator Surface Conductance

Surface conductance of outdoor insulators exposed to pollution and moisture from rain or fog is related to two aspects of insulator application: 1) possibility of insulator flashover and 2) duration and severity of surface arc discharges. This paper will discuss some of the experience with monitoring the surface conductance of porcelain and synthetic insulation under voltage stress and exposed to outdoor weathering in various locations in the U. S. Simple flat surfaces mounted at a 30° angle from the horizontal and some shed-type insulators have been followed in this study. Recordings have been made over periods of several years, comparing results with low and high voltage stress. Results of these outdoor tests are also compared with results of tests of similar surfaces in a synthetic salt-fog chamber.