Highly Sensitive and Selective Acetylene CuO/ZnO Heterostructure Sensors through Electrospinning at Lean O₂ Concentration for Transformer Diagnosis

Abstract

Acetylene (C₂H₂) is a gas that can cause explosions in transformers even at low concentrations. Gas chromatography (GC) or photoacoustic spectroscopy (PAS) have been used to detect C₂H₂ during dissolved gas analysis (DGA), but they are not suitable for monitoring numerous transformers at substations. Even though metal oxide semiconductor (MOS) based C₂H₂ sensors have drawn much attention as a potential solution, existing MOS-based C₂H₂ sensors have low sensitivity toward C₂H₂ in the transformer environment (<2% O₂ concentrations). This study develops high-performance C₂H₂ gas sensors for DGA using a heterostructure of CuO/ZnO (CZ) via the electrospinning process. Performance of various ratios of CZ composite nanofibers are compared in a transformer-like environment, and the optimal composition of CZ nanofibers for detection of C₂H₂ at 2% O₂ concentration is proposed. The CuO:ZnO = 8:2 (CZ2) sensor achieves the highest response (<i>R</i>_g/<i>R</i>_a = 7.6 against 10 ppm of C₂H₂) toward low concentration of C₂H₂ at 200 °C with good stability (>10 h). In addition, the CZ2 sensor also shows a high selectivity (>5 times) to coexisting transformer oil gases which are H₂, CH₄, C₂H₄, C₂H₆, CO, and CO₂. Overall, this study is the first to demonstrate a high performing DGA sensor under 2% O₂ concentration that can provide a practical solution to monitoring the low concentration of C₂H₂ in transformers effectively.