SF6 concentration sensor for gas-insulated electrical switchgear

• We developed a low-cost insitu multi-sensor system for measuring the composition of a binary gas mixture.
• High accuracy concentration measurements of binary gas mixtures are possible under field conditions.
• We map out the density and temperature distribution encountered in a typical GIS element under operation.

The use of SF6-N2 gas mixtures in gas insulated electrical switchgear (GIS) is becoming more wide-spread. This is motivated by the reduction of environmental impact associated with SF6 emission and the increasing number of GIS located in low temperature environments where pure SF6 cannot be employed. We present a cost-efficient sensor system that tracks gas composition based on a measurement of pressure, density and temperature. To reach the necessary measurement accuracy, a reliable calibration routine was developed. The robustness and high-end performance of the sensor system is demonstrated on a lab setup in which the thermal and convective conditions that develop in a GIS under operation can be reproduced.