Detection Of Transformer Fault Gas C₂H₂ Based On Quartz Enhanced Photoacoustic Spectroscopy

Transformer is one of the core components of power system,the analysis of dissolved gas in transformer oil can find the existing early failure,and effectively prevent the huge loss caused by power grid breakdown.In the event of a transformer failure,the transformer oil will crack to produce different gases,such as methane,acetylene,hydrogen,and so on.Among them,acetylene（C₂H₂）is one of the important characteristic gases of transformer failure.Therefore,real-time detection of C₂H₂concentration is of great significance for auxiliary judgment of transformer fault.Quartz Enhanced Photoacoustic Spectroscopy（QEPAS）is a gas detection technique based on the photoacoustic effect.With large detection range,and fast detection response,quartz enhanced photoacoustic spectroscopy is widely used in the field of gas detection.This paper mainly studies the detection of transformer fault gas.Through the establishment of quartz enhanced photoacoustic spectrum detection system,the signal is processed by phase-locked amplifier,and the tuning fork coupling resonance tube module is optimized to realize the high sensitivity detection of acetylene gas.Firstly,in the theoretical research part,the transformer fault types and gas are analyzed,and for the dissolved gas in transformer oil,the gas detection technology is classified and compared,the gas molecular absorption theory is analyzed,through the analysis of the photoacoustic effect,the technical principle of photoacoustic spectrum is studied in detail;The piezoelectric effect of quartz tuning fork and the resonant enhancement theory of QEPAS technology are analyzed.Secondly,the transformer fault gas acetylene detection system based on QEPAS was built,the transformer fault gas acetylene and other influence gas absorption lines were analyzed,the light source,tuning fork,resonance tube and lock amplifier and other experimental equipment were selected,the circuit and signal processing process of the lock amplifier were analyzed.The quartz tuning fork,one of the cores of the gas acetylene detection system for transformer faults,is optimized.Based on the finite element method,the quartz tuning fork model is established and its vibration modes are simulated,and the resonant frequencies corresponding to different sizes of the quartz tuning fork are simulated.Taking standard quartz tuning fork and custom tuning fork as the research object,the coupling model of tuning fork and resonant tube is established.The coupling position of tuning fork and resonant tube,the length and inner diameter of the resonant tube are studied.The optimal parameters of the coupling model of two kinds of tuning fork and resonant tube are obtained from the analysis results,and the parameters selected in the transformer fault gas acetylene detection experiment are determined.Finally,through the establishment of quartz enhanced photoacoustic spectrum gas detection system for experiments,the use of standard tuning fork to detect the transformer fault gas acetylene,through the experiment analysis of the system performance,to achieve the transformer fault gas acetylene 1.22ppm detection limit,optimize the modulation depth of the system,complete the acetylene concentration measurement.The influence of temperature and pressure on transformer fault gas acetylene detection system is also discussed.