摘要
传统定时限零序过电流保护定值需躲过线路最大电容电流,定值较高,不能可靠保护小电阻接地系统的高阻接地故障。该文分析了小电阻接地系统单相接地故障时零序电流的分布特征,发现无论故障点过渡电阻大小,故障出线零序电流幅值与中性点零序电流接近,均大于健全出线零序电流十倍以上。由此提出一种高灵敏度的阶段式零序过电流保护方法,即将现有零序过电流保护按照特定原则分解为多段定时限零序过电流保护,降低最低段保护启动电流定值,提高高阻接地故障保护灵敏度,利用各出线保护之间的横向配合实现低阻接地保护的选择性。结合工程实际条件给出了各段保护电流定值与动作时限定值的具体整定原则和计算方法,经Matlab仿真及现场实际故障数据验证,保护耐受过渡电阻能力可达1.5kW左右。该方法不需要重新开发、安装新装置,利用系统原有保护装置经过合理的设置与整定即可实现,方便现场应用。
Due to the over-rated value in a low-resistance grounding system,the high-resistance earth fault cannot be reliably protected by traditional definite-time zero-sequence overcurrent protection.Within this context,this work evaluated the distribution characteristics of zero-sequence currents in the case of single-phase-to-ground fault in a low-resistance grounding system.The results showed that regardless of the transition resistance of the fault point,the magnitude of zero-sequence current in the fault feeder was always close to the zero-sequence current of the neutral point,which was more than ten times higher than the zero-sequence current in the healthy line.Moreover,a high-sensitivity zero-sequence overcurrent protection method was proposed to decompose the existing zero-sequence overcurrent protection into multi-stage definite-time zero-sequence overcurrent protection.During this novel protection method,the algorithm decreased the minimum start current setting value,increased the protection sensitivity at high-resistance ground fault,and improved the protection selectivity at low-resistance earth fault with the use of horizontal coordination between each outlet protection.Therefore,the specific setting principles and calculation method of the specific value of the protection current setting and the operation time of each stage were given according to engineering reality.And the simulation proof of maturity of the protection tolerant transition resistance was almost up to 1.5 kW.The method did not need to re-develop and install a new device,and the original protection device of the system could be realized through reasonable setting,which was convenient for field application.
作者
薛永端
汪洋
徐丙垠
XUE Yongduan;WANG Yang;XU Binyin(College of New Energy,China University of Petroleum(East China),Qingdao 266580,Shandong Province,China;State Grid Huaian Power Company,Huai’an 223001,Jiangsu Province,China;Smart Research Center(Shandong University of Technology),Zibo 255000,Shandong Province,China)
出处
《中国电机工程学报》
EI
CSCD
北大核心
2020年第19期6217-6226,共10页
Proceedings of the CSEE
基金
国家自然科学基金项目(51477184)。
关键词
小电阻接地系统
零序电流
高阻接地故障
阶段式保护
横向配合
low-resistance grounding system
zero-sequence current
high resistance earth fault
stage protection
crosswise cooperation
