Conversion of Relative Humidity in SF6 Gas-Insulated Equipment at Different Temperatures Based on the Polanyi Adsorption Potential Theory

Moisture in SF₆ gas-insulated equipment (GIE) affects the dielectric withstand strength of the insulation material in it, so moisture measurement constitutes a major part of an effective maintenance program for GIE. The relative humidity (RH) of SF₆ in GIE reflects the insulation property of dielectric intuitively. But in most cases, only transient RH is not sufficient for us to make a good maintenance program. What we are interested in is RH for the entire range of the expected operating temperatures. Therefore, the RH at desired temperatures is to be conversed from the on-line value, and in such a course, we have to take the so called "adsorption effect" into account. This paper describes the adsorption effect by relationship between adsorption potential and adsorption space based on the Polanyi adsorption potential theory. The procedure of plotting the curve of "adsorption potential-adsorption space" is presented. Based on the on-line monitoring, the RH of SF₆ at different temperatures is calculated by using the curve and the corresponding results can be applied to forecasting the insulation property of GIE