Highly sensitive fiber-enhanced Raman spectroscopy for simultaneous detection of SF6 decomposition

Abstract

As the insulating medium, sulfur hexafluoride (SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ) is widely applied in gas insulation equipment. Over longterm operation, the solid insulation of the equipment is damaged by PD, causing it to react with SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> to generate COS and CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> which are critical SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> decomposition products inside the equipment. The detection of these two SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> decomposition products can help in assessment of the type and severity of insulation defects. Compared to the absorption spectroscopy and photoacoustic spectroscopy, FERS can using a single wavelength laser to simultaneously achieve the high sensitivity detection of mixture gases. In this paper, a highly sensitive SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> decomposition based on fiber-enhanced Raman spectroscopy is built up. The Raman spectroscopy of COS and CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> was acquired. The characteristic peak of COS at 859 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and that of CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> at 909 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> were observed respectively. We study the relationship between laser power, pressure of fiber core and Raman scattering intensity, experimentally. The Raman scattering intensity is linear related to laser power and pressure. The response time of FERS which includes the filling time and evacuating time. was also examined. The filling time of the fiber is defined as the point when the intensity of the Raman peak does not change. FERS is promising to achieve the online monitoring technique to detect the SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> decomposition components with highly selective and sensitive.