换流变阀侧干式套管表带触指失效过程分析

在超、特高压电力系统中,换流变压器阀侧干式套管作为换流变压器连接换流阀的关键设备,其安全运行直接关系到电力系统的可靠性。近年来,国内外发生多起由于电接触失效而导致的套管过热和放电故障,因此有必要对套管载流连接结构的失效机理开展研究分析。该文以±500kV换流变阀侧套管的过热故障为例,计算分析套管在实际运行电流下表带触指的摩擦行程,采用扫描电镜(scanning electron microscope, SEM)和能量色散光谱仪(energy dispersive spectrometer,EDS)对表带触指失效前后的表面和断面进行形貌分析和成分分析,提出表带触指在套管内的劣化机理。研究发现:铜导杆接触区域没有镀银是缩短触指寿命的主要原因,长期的机械磨损和SF6气体分解产物对触指的腐蚀是导致触指劣化的重要因素,相关结论可为套管电连接设计、选型和过热型故障分析提供理论依据。

Analysis on the Deterioration Behavior of Electrical Contact Structure Used in Converter Transformer RIP Bushings

Converter transformer resin impregnated paper(RIP) bushing is used as a key equipment of the converter transformer to connect the converter valve, and its safe operation is directly related to the reliability of power system. In recent years, there have been several overheating and discharge faults of RIP bushing caused by the deterioration of electrical contact at home and abroad, so it is necessary to analyze the failure mechanism of the electrical contact used in RIP bushing. In this paper, taking the overheating fault of ±500 kV RIP bushing as the object, the friction travel of the contacts used in RIP bushing under the actual operating current was calculated. Morphology and composition of the contacts, before and after deterioration, from the surface and cross perspective was analyzed by using scanning electron microscope(SEM) and energy dispersive spectrometer(EDS), and finally the degradation mechanism of the electrical contacts was proposed. The study found that the lack of silver plating on the surface of the copper conductor is the main reason for shortening the life of the contacts, and long-term mechanical wear and corrosion of SF6 gas decomposition products are important factors leading to the deterioration of contacts. The conclusion can provide a theoretical basis on the overheating failure analysis and its protection for RIP bushing.