High-sensitivity dynamic analysis of dissolved gas in oil based on differential photoacoustic cell

• A high-sensitivity dynamic analysis technology based on low-noise differential photoacoustic (PA) cell (DPAC) is presented for real-time monitoring of dissolved gas separation process. • The airflow noise is filtered out by optimizing the band-stop filter characteristics of the muffler. • Differential processing is used to reduce noise with the same characteristics in two PA tubes. • Both the differential detection method and the muffler reduce the noise during headspace degassing by more than 80%. • The result indicates that the minimum detection limit of the system for dissolved C 2 H 2 is 0.1 μL/L, which provides a technical solution for extra-early transformer faults diagnosis. In order to realize real-time online monitoring of dissolved trace gas in transformer oil, a high-sensitivity dynamic analysis technology based on a low-noise differential photoacoustic (PA) cell (DPAC) is proposed. The characteristic gas dissolved in oil is separated by the means of headspace degassing and then pumped into the DPAC. The emitted laser light is amplified by an erbium-doped fiber amplifier (EDFA) and reflected in the DPAC to form a double-pass excitation enhancement. The DPAC with two expansion mufflers is equipped. The airflow noise in the two PA tubes with symmetrical design is basically the same. Differential processing is used to reduce the noise. In addition, the airflow noise with the same frequency as the PA signal is filtered by optimizing the band-stop filtering characteristic of mufflers. The experimental results show that both the differential detection method and the muffler reduce the noise during headspace degassing by more than 80%. The detection limit of the system for dissolved acetylene (C 2 H 2 ) in oil reaches 0.1 μL/L. The technical solution has the advantages of high detection accuracy and fast response speed, which provides a technical solution for dynamic dissolved gas analysis.