Abstract
Analysis of decomposition gas products offers the most promising method for the diagnosis of gas-insulated transformers due to its capability of detecting the two important faults, overheat and discharge, in transformers. Although many studies have been made on SF6 decomposition, quite few are readily available to gas-insulated transformers because of the variety in their faults.
An experimental survey over the main components of the decomposition products generated by various faults in gas-insulated transformers was carried out through simplified model tests. The modeling was made on three important phenomena of the faults in transformers, namely, overheat, partial discharge and electrical arc, taking the actual materials related to each fault into account. Gaschromatograph and ionchromatograph were employed in the analyses of the decomposition products.
Decomposition gases characteristic to each fault were identified by the experiments. For example, SF6 decomposition by an overheat of a metal gives SO2 and an overheat of winding insulation CO2 and CO. Discharges in SF6 gas have given characteristic SO2F2 gas while arc currents at insulated wires have shown SF4 gas instead. A development of a diagnostic method for gas-insulated transformers is under way by use of a quantitative study on this results.
