Reconstructing and extracting information on SF6decomposition characteristic components induced by partial overthermal fault in GIE

Abstract

Sulfur hexafluoride (SF6) gas-insulated equipment (GIE) has been widely used in extra/ultra high voltage power transmission systems. During its operation, GIE inevitably experiences partial overthermal faults caused by poor contact. In this study, the SF6 decomposition characteristic of partial overthermal faults was used to solve problems that cannot be detected effectively in GIE. First, a large number of experiments were conducted on an SF6 overthermal decomposition system to obtain the overthermal decomposition characteristic of SF6 below 400 °C. Then, from the perspective of the physical significance of engineering, three feature parameters, namely, total decomposition amount, effective formation rate, and ratio of characteristic components, were proposed to reveal the deterioration degree of the gas insulation medium as well as to represent the development trend and severity of a partial overthermal fault. Results show that total decomposition amount CT, CT1, and CT2 can depict the degradation degree of the GIE insulation medium and the carbonic metal structure caused by a partial overthermal fault, which can be a good index to differentiate partial overthermal fault temperatures. The effective formation rate of each characteristic component RRMS is closely related to temperature and can reflect the development trend of a partial overthermal fault. The feature ratio CO2/(SO2F2+SOF4+SOF2+SO2+H2S) can reveal whether a partial overthermal fault involves organic insulation materials. H2S/(SO2F2+SOF4) can depict the severity of a partial overthermal fault. Log10(SOF2+SO2)/(SO2F2+SOF4) and its effective value TCRRMS3 can represent the deterioration degree of GIE and provide excellent correlation with the severity of a partial overthermal fault, and thus, it can be used to evaluate the severity of a partial overthermal fault quantitatively.