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。
The sensitivity of three common stator grounding protection schemes based on the third-harmonic voltage is compared and analyzed based on the parameters of a 300 MW turbine generator,which shows that the sensitivity of stator grounding protection schemes may be insufficient in the middle of the stator winding if the turbine generator is connected with the grounding transformer. Considering the frequent maloperation present in the existing stator grounding protection schemes based on the third-harmonic voltage,the causes of third-harmonic voltage variation of the generator terminal and the generator neutral point are analyzed. Based on the above research,an improved stator grounding protection scheme based on third-harmonic voltage variation component differential principle is proposed. The variation of the third-harmonic voltage of the generator terminal are corrected and then adopted to construct the differential criterion with the variation of the third-harmonic voltage of the generator neutral point,which can effectively distinguish the stator grounding faults from the normal change of generators＇ third-harmonic voltage. In order to avoid false tripping caused by harmonic voltage changes at high voltage side,a floating threshold value is also set according to the variation of the third-harmonic voltage at high voltage side. Simulative results show that the proposed scheme is theoretically correct and slightly affected by the changes of generator operating state with high sensitivity.
出处
《电力自动化设备》
EI
CSCD
北大核心
2017年第10期177-183,共7页
Electric Power Automation Equipment
关键词
汽轮发电机
3次谐波电压
定子接地保护
继电保护
变化量
灵敏度
仿真
steam-turbine-generator
third-harmonicvariation component
sensitivity
simulationvoltage
stator ground protection
relay protection
