SF6 density-and-viscosity sensing in Gas Insulated Switchgear using MEMS resonator

SF
₆
based Gas Insulated Switchgear (GIS) are widely used for High Voltage (HV) applications. Due to the environmental impact of SF
₆
gas, strict regulations have been laid to monitor their use and to restrict their emission from switchgears. Quartz based resonant density sensor is the best technology commercially available today for SF
₆
monitoring. Frequency response of the sensor is a function of both density and viscosity. However, each sensor contains a matched pair of quartz crystals for temperature compensation. The accuracy of the density sensor is limited by the extent of mismatch between the quartz crystals which determines the minimum detectable change in SF
₆
density. Calibration makes the sensor gas-specific and dependent on the environmental conditions. We propose a MEMS based resonator for in-situ SF
₆
viscosity measurement that can be used as an input to the existing gas density sensor. It will make the matched pair of quartz crystal redundant resulting in more accuracy.