基于紫外光谱检测的GIS内多类故障早期预警

气体绝缘开关(GIS)故障预警强调异常识别的实效性和现场适用性，是精确诊断的基础。研究GIS内局部放电(PD)及过热故障的统一预警方法具有重要意义。提出将SO₂作为GIS内部两类故障公共的特征分解物，并应用紫外光谱(UV)测量SO₂实现多故障早期预警。一阶导数法和Savitzky-Golay滤波被用于快速基线校正和光谱平滑，290～310 nm被选为特征区进行SO₂检测及定量。UV检测可避免诸如SF₆及SOF₂、SO₂F₂等分解物的干扰，便于从复杂的SF₆分解物组分中识别微量SO₂特征，测量系统结构简单、维护成本低、适于现场检测。通过模拟SF₆气体在两类PD缺陷及200～400 ℃过热条件下的分解实验，证实所提UV预警方法的有效性：两类GIS故障条件下都会稳定的生成SO₂。对UV预警后的故障诊断，借助傅里叶变换红外光谱仪及气相色谱仪，确认PD及过热故障下的分解物组分存在差异，并据此简要分析了故障类型辨识方法。PD分解物以SOF₂和SO₂F₂为主，SO₂含量远小于SOF₂，放电涉及环氧树脂时含碳分解物含量上升。过热材质为不锈钢时，SF₆约在300 ℃发生分解，300～400 ℃内的过热分解物主要为SO₂和SOF₂，350 ℃以上SO₂生成速率明显快于PD时。随着GIS内故障持续恶化，SO₂含量均呈现稳定上升趋势。在UV预警后，可利用获得的SO₂生成特性初步辨识故障类型。

Early Warning for Various Internal Faults of GIS Based on Ultraviolet Spectroscopy

As the basis of accurate diagnosis, fault early-warning of gas insulation switchgear (GIS) focuses on the time-effectiveness and the applicability. It would be significant to research the method of unified early-warning for partial discharge (PD) and overheated faults in GIS. In the present paper, SO₂ is proposed as the common and typical by-product. The unified monitoring could be achieved through ultraviolet spectroscopy (UV) detection of SO₂. The derivative method and Savitzky-Golay filtering are employed for baseline correction and smoothing. The wavelength range of 290～310 nm is selected for quantitative detection of SO₂. Through UV method, the spectral interference of SF₆ and other complex by-products, e.g. SOF₂ and SOF₂, can be avoided and the features of trace SO₂ in GIS can be extracted. The detection system is featured by compacted structure, low maintenance and satisfactory suitability in filed surveillance. By conducting SF₆ decomposition experiments, including two types of PD faults and the overheated faults between 200～400 ℃, the feasibility of proposed UV method has been verified. Fourier transform infrared spectroscopy and gas chromatography methods can be used for subsequent fault diagnosis. The different decomposition features in two kinds of faults are confirmed and the diagnosis strategy has been briefly analyzed. The main by-products under PD are SOF₂ and SO₂F₂. The generated SO₂ is significantly less than SOF₂. More carbonous by-products will be generated when PD involves epoxy. By contrast, when the material of heater is stainless steel, SF₆ decomposes at about 300 ℃ and the main by-products in overheated faults are SO₂ and SO₂F₂. When heated over 350 ℃, SO₂ is generated much faster. SO₂ content stably increases when the GIS fault lasts. The faults types could be preliminarily identified based on the generation features of SO₂.