Portable ppb-level acetylene photoacoustic sensor for transformer on-field measurement

Abstract

Acetylene (C2H2) is considered as one of the typical decomposition gas of transformer oil to measure the severity of oil-immersed transformer fault. Quantitative measurement of trace C2H2, especially on-field measurement, has long been the center of fault diagnosis field. In this work, a ppb-level photoacoustic sensor for C2H2 was developed for transformer insulation status detection. Firstly, combined degassing method was employed to extract dissolved gas from oil. According to known Ostwald coefficient at certain temperature, the concentration of dissolved C2H2 in oil can be calculated by measuring the concentration of extracted C2H2. Then, a quantitative detection system for C2H2 based on laser photoacoustic spectroscopy was established in this work. The concentration of the extracted C2H2 can be reversed by obtained photoacoustic signal. Experimental results indicate that the detection limit of proposed system can reach ~3.4 ppb. Besides, compared with the quantitative detection results of GC, the relative error of proposed sensor could meet relevant requirements. Experimental fruitions testify the feasibility of proposed sensor for field application, and the results of this work may serve as a guide of insulation fault diagnosis for oil-immersed transformer.