Dissolved hydrogen measurement with solid-state sensors in liquids using dynamic drift elimination techniques

Specialized techniques such as Dissolved Gas Analysis (DGA) have historically been used to measure gas concentration and successfully indicate faults in equipment such as oil-filled transformers. A palladium based, solid state, on-line hydrogen sensor is presented that can operate immersed directly in various insulating fluids. Its performance is compared with manual sample extraction and offline analysis by laboratory gas chromatographs. Results of lab qualification as well as extended field testing have been utilized to develop algorithms that compensate for sensor drift, temperature-dependent gas solubility changes, and liquid type. The intrinsic sensor drift is eliminated using a reference cycle approach that does not require any external gas application or user intervention. Its efficacy has been tested in sensors operating in both the liquid and gas-phase and can eliminate cross-sensitivity. In particular, the use of palladium alloys for measuring H₂ can be confounded by known interference gases and sensor poisons such as O₂, CO, and H₂S. This paper will highlight the ability of this technique to not only remove intrinsic sensor drift, but also eliminate cross-interference effects from gases such as CO, H₂S, etc.