A New Concentration Detection System for SF6/N2 Mixture Gas in Extra/Ultra High Voltage Power Transmission Systems

This paper develops a new detection system, for the first time, to detect the gas concentrations of the SF 6 /N 2 mixture in extra/ultra-high voltage power transmission systems. The concentrations of SF 6 and N 2 are calculated from the thermal conductivity function of the mixture gas. The main contribution of this work is that a specially-designed thermostatic chamber with adaptive temperature controller is developed to ensure constant pressure of the gas flowed through the thermal conductivity sensor. Another contribution is the combination of multiple sensors (e.g. humidity and electrochemical sensors), which enables the detector to address the penetration effects of H 2 O and O 2 in the SF 6 /N 2 mixture. Experimental evaluation results using the prototype demonstrated that satisfactory accuracy (±1% of the measurement error) has been achieved for the concentration detection of the SF 6 /N 2 mixture under variable operation conditions. Compared with existing detection techniques, the proposed detector not only can detect the SF 6 /N 2 concentration by taking the air infiltration effect into account, but also reduce the cost.