Highly Sensitive and Selective Acetylene CuO/ZnO Heterostructure Sensors through Electrospinning at Lean O<sub>2</sub> Concentration for Transformer Diagnosis
Mi‐Hee Jung, Minjun Kwak, Jung Hwan Ahn, Ji‐Yoon Song, Hohyung Kang, Hee‐Tae Jung
Abstract
Acetylene (C 2 H 2 ) 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 C 2 H 2 during dissolved gas analysis (DGA), but they are not suitable for monitoring numerous transformers at substations. Even though metal oxide semiconductor (MOS) based C 2 H 2 sensors have drawn much attention as a potential solution, existing MOS-based C 2 H 2 sensors have low sensitivity toward C 2 H 2 in the transformer environment (<2% O 2 concentrations). This study develops high-performance C 2 H 2 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 C 2 H 2 at 2% O 2 concentration is proposed. The CuO:ZnO = 8:2 (CZ2) sensor achieves the highest response ( R g / R a = 7.6 against 10 ppm of C 2 H 2 ) toward low concentration of C 2 H 2 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 H 2, CH 4, C 2 H 4, C 2 H 6, CO, and CO 2 . Overall, this study is the first to demonstrate a high performing DGA sensor under 2% O 2 concentration that can provide a practical solution to monitoring the low concentration of C 2 H 2 in transformers effectively.