Study on feedback stabilization technology of acetylene gas photothermal interferometric sensing system

Power transformer is the key to the stable operation of power system. Transformer oil play an insulative and radiating role in power transformer, in a long time of operation, transformer oil due to discharge or overheating will produce trace methane, acetylene and other gases dissolved in it, when the concentration of dissolved gas in transformer oil is too high, seriously affecting the safety of the transformer.At present, the detection technology of dissolved gas in transformer oil includes electrochemical sensing, gas chromatography, infrared spectrum detection and photoacoustic spectrum detection. They have problems such as poor selectivity, long measurement time, unstable measurement and large probe volume. Interference of photothermal detection technology has some advantages in these aspects, but in photothermal spectroscopy, the detection working point is prone to drift when the environmental conditions change, which affects the stability of the measurement system. A commercial servo control instrument is used to feedback control the interference system, and the incident wavelength of probe laser can be locked at the intersection of the interference, achieving stable control of the working point. In order to achieve a miniaturized photothermal spectrum detection system, this paper will complete the PI feedback stabilization in the Labview based on the PID servo control principle, aiming at the problem of slowly changing working point drift in the photothermal interference system, and uses the probe laser’s phase servo stability control system based on the Labview to replace the high cost high-speed feedback control system, and builds the photothermal interference gas sensing system.