Decomposition Products Detection of Sulfur Hexafluoride Based on
Frequency Comb Spectroscopy
LIU Ting-ting1, SHEN Xu-ling1, REN Xin-yi1, WEN Zhao-yang1, YAN Ming1, 2, ZENG He-ping1, 2*
1. State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
2. Chongqing Key Laboratory of Precision Optics, Chongqing Institute of East China Normal University, Chongqing 401121, China
Abstract：With the rapid development of power systems towards high voltage, large capacity and application sininformation technology, the efficient operation and maintenance of power equipment is of great significance to ensure the safe operation of power systems and steady economic growth. Detecting sulfur hexafluoride gas decomposition products is an effective method for leak detection and fault diagnosis in electrical insulation equipment. Dual-comb spectroscopy, derived from optical frequency combs, has the advantages of high resolution, high precision, wide spectrum and high speed, and is expected to provide a reliable method for quantitative analysis of characteristic gases in leakage troubleshooting of power equipment. In this paper, a dual-comb spectroscopy detection equipment was built by using two integrated erbium-doped fiber optical combs. With precise frequency control and fine temperature control, the frequency fluctuation of the repetition rate was decreased from 18.37 Hz to 607.72 μHz and the stability of the comb teeth was improved to 10-12. The long-term stability and integration enabled the combs strong immunity to environmental disturbance and the combs maintained high coherence within more than 2 hours in outdoor operation as the repetition rate and the carrier envelope phase offset signals of the combs kept phase-locked. In terms of spectral detection, the mixture of CO and CO2 was measured with the help of an ultra-sensitive multi-pass cell and as a result, the absorption peaks of CO and CO2 within the 1 540～1 590 nm band were simultaneously measured with 1 pm spectral resolution on the ms time scale. Taking the characteristic absorption peaks of CO at 1 585.47, 1 581.946 nm, and CO2 at 1 580.5, 1 579.575 nm, for example, the molecular densities of CO and CO2 could be easily derived from Lorentzian fitting, and the uncertainties were reduced to 0.32% and 0.24%, respectively, using multi-peaks fitting, which were nearly one order of magnitude lower than that of single-peak measurement (2%). Our research promotes the application of dual-comb spectroscopy and the related system in non-contact real-time detection of characteristic gases in power equipment. Compared with the traditional contact detection technology, which has the shortcomings of single gas detection, long integration time, and difficulty in long-term online real-time monitoring, the dual-comb spectroscopy is advantaged in simultaneously multi-peaks detection of diverse gases in ms order of time, which can shorten detection time and improve the accuracy. In a word, dual-comb spectroscopy provides an effective method for timely troubleshooting and fault diagnosis for leak detection in power equipment.
Key words：Optical frequency comb; Dual-comb spectroscopy; Characteristic gas detection
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