Research On Transformer Dissolved Gas-in-oil Analysis Based On Photoacoustic Spectroscopy Technology

In order to guarantee the reliability, safety and stability of the operation of power grids, the running conditions of large oil-immersed power transformers in the power grids, especially those in important places, are expected to be continuously monitored. Currently, the most reliable and effective measure to diagnose potential glitches and online-monitor the running conditions of oil-immersed transformer is the Analysis of Dissolved Gas in Transformer oil, shorten as DGA Measurement.We can detect the current running conditions of the transformer, distinguish fault types and get important evidence to overhaul and evaluate the performance of faulty transformers by analyzing dissolved gas in transformer oil. Because it has a high resolution and large dynamic range, photoacoustic Spectroscopy Technology can be applied to the online-monitoring of dissolved gas in oil. This paper presents a photoacoustic spectroscopy of multicomponent gas mixture detecting system with an optic-fiber acoustic sensor as photoacoustic microphone, a tunable near-infrared broadband fiber laser combining fiber amplifiers as light source, a near-infrared all-fiber photoacoustic spectrometer, a resonant photoacoustic cell as detection place, combining frequency modulation and wavelength scanning technology. The system is applied in online analysis of dissolved gas in transformer oil, obtaining a simultaneous measure of gases resulting from transformer glitches such as CH4, C2H2 and CO2, with limit detection sensitivity reaching 434.783ppm,28.249ppb and 16.260ppm respectively by using three different wavelength,1529.39nm,1531.59nm and 1572.34nm. In order to improve the limit detection sensitivity of CH4 gas, this paper proposes to use the 1650.96nm, which CH4 has a stronger ability to it, that will improve the sensitivity limit of CH4 gas to 7.463ppm, increased by nearly two orders of magnitude.Transformer DGA detecting platform is based on near-infrared Photoacoustic Spectroscopy of multicomponent gas detecting system, which is the experimental platform of this paper. Through theoretical analysis and calculation, repeated experiment results show that, the system can be applied to Transformer DGA multi-gas online measurement and shows advantages of Photoacoustic Spectroscopy Technology applying in DGA Measurement, by obtaining a continuos and high sensitive real-time measurement. To achieve higher system's detection sensitivity limit and the prospect to a new idea of Photoacoustic Spectroscopy DGA, we plan to use SOA apparatus, and in-depth research optical fiber microphone with higher performance in the future.