大型汽轮发电机3次谐波电压定子接地保护方案的研究与改进

发布时间：2019-01-03 13:10

【摘要】：基于一台300 MW汽轮发电机的参数,对常用的3种3次谐波电压定子接地保护方案进行灵敏度对比分析。分析结果表明大型汽轮发电机采用接地变压器接地方式时,现有的3次谐波电压定子接地保护在定子绕组中部的灵敏度仍然不足。考虑现有3次谐波电压定子接地保护存在误动较多的问题,分析了导致发电机机端、中性点3次谐波电压变化的原因。在此基础上,提出一种改进型3次谐波电压变化量差动原理定子接地保护方案。该方案对机端3次谐波电压变化量进行校正后与中性点3次谐波电压变化量构成差动判据,可有效区分定子接地故障与发电机3次谐波电压的正常波动。该方案还根据高压侧3次谐波电压的变化量增加了浮动的保护启动门槛,避免因高压侧3次谐波电压变化而导致的误动。仿真结果表明所提方案理论正确,灵敏度较高,受机组运行变化状态的影响小。
[Abstract]:Based on the parameters of a 300 MW turbogenerator, three common third harmonic voltage stator grounding protection schemes are compared and analyzed. The results show that the sensitivity of the third harmonic voltage stator earthing protection in the middle of the stator winding is still insufficient when the earthing mode of the large turbogenerator is adopted by the earthing transformer. Considering that the third harmonic voltage stator grounding protection has many misoperation problems, the causes of the third harmonic voltage variation in generator terminal and neutral point are analyzed. On this basis, an improved third harmonic voltage variation differential stator earthing protection scheme is proposed. After correcting the third harmonic voltage variation at the end of the machine, the scheme constitutes a differential criterion with the third harmonic voltage variation at the neutral point, which can effectively distinguish the normal fluctuation of the stator grounding fault from the third harmonic voltage of the generator. According to the variation of the third harmonic voltage in the high voltage side, the threshold of floating protection is increased to avoid the misoperation caused by the variation of the third harmonic voltage on the high voltage side. The simulation results show that the proposed scheme is correct in theory, high in sensitivity and less affected by the operating state of the unit.
【作者单位】：南京国电南自电网自动化有限公司;
【分类号】：TM311

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