Detection of ultra-low concentration acetylene gas dissolved in oil based on fiber-optic photoacoustic sensing

Dissolved acetylene gas in oil is the characteristic gas to distinguish overheating and discharge faults of transformer. To realize the detection of ultra-low concentration acetylene in transformer oil, a photoacoustic (PA) gas detection system based on ultra-high sensitive fiber-optic acoustic sensing technique was designed. In order to amplify the power of the laser, an Erbium-doped fiber amplifier (EDFA) was utilized, thereby increasing the intensity of the PA excitation signal. A cantilever based fiber-optic acoustic sensor was utilized to detect the generated PA signal. the interference of carbon dioxide and water vapor on the detection of ultra-low concentration acetylene was studied through analyzing the absorption spectrum. By optimizing the laser modulation parameters, the interference of the interfering gases on the acetylene absorption signal is reduced. Experimental results show that the response time of the system is 9 min with the headspace degassing based oil–gas separation method. The ultra-low concentration of dissolved acetylene gas in oil was tested, and the detection limit reached 0.05 μL/L. The technical solution provides a new solution for transformer fault detection.