基于低频暂态零序电流畸变率的灵活接地系统高阻接地保护  

High-resistance Grounding Protection for Flexible Grounded Systems Based on Low-frequency Transient Zero-sequence Current Distortion Rate

作　　者：李晓波[1] 张世乐 彭超红 LI Xiaobo;ZHANG Shile;PENG Chaohong(School of Electrical Engineering,China University of Mining and Technology,Xuzhou 221116,China)

机构地区：[1]中国矿业大学电气工程学院,江苏省徐州市221116

出　　处：《电力系统自动化》2024年第13期171-183,共13页Automation of Electric Power Systems

摘　　要：灵活接地系统中,基于稳态故障特征构成的单相接地保护普遍存在耐过渡电阻能力低的问题,并联小电阻投入后该问题进一步突出。文中研究了并联小电阻投入后故障线路与非故障线路低频暂态零序电流中暂态直流分量比值关系,发现暂态直流分量比值仅与对地电容有关。分析了故障线路与非故障线路低频暂态零序电流畸变率之间比值关系,进一步提出了一种基于低频暂态零序电流畸变率的灵活接地系统单相高阻接地故障选线方法。通过比较特定时间窗口内各馈线低频暂态零序电流畸变率的大小实现故障选线,并可准确区分母线故障与出线故障。该方法能够避免零序电压互感器断线与零序电流互感器极性反接的影响,且受故障距离影响小。同时,该方法采用暂态故障特征构成选线判据,有利于克服并联小电阻投入后稳态故障分量微弱的问题,对互感器精度要求不高。最后,通过实时数字仿真和实验平台分别验证了所述方法的准确性和有效性。In flexible grounded systems,single-phase grounding protection based on steady-state fault characteristics generally has low resistance to transition resistance,and this problem is further exacerbated after the connection of parallel small resistors.This paper studies the relationship between the ratio of the transient DC component in the low-frequency transient zero-sequence current of faulty and non-faulty lines after the connection of parallel small resistors,and finds that the transient DC component ratio is only related to the capacitance to ground.The relationship between the ratio of low-frequency transient zero-sequence current distortion rates of faulty and non-faulty lines is analyzed,and a method for line fault selection based on low-frequency transient zero-sequence current distortion rates in flexible grounded systems with high-resistance grounding faults is further proposed.Fault line selection is achieved by comparing the magnitude of low-frequency transient zero-sequence current distortion rates of each feeder within a specific time window,and busbar faults and outgoing line faults can be accurately distinguished.This method can avoid the impact of zero-sequence voltage transformer disconnection and zero-sequence current transformer polarity reversal,and is less affected by fault distance.At the same time,this method uses transient fault characteristics to form a line selection criterion,which is beneficial for overcoming the weak steady-state fault component after connection of parallel small resistors,and has low requirements for instrumental transformer accuracy.Finally,the accuracy and effectiveness of the method are verified through real-time digital simulation and experimental platforms.

关 键 词：配电网 灵活接地系统 低频暂态 零序电流 零序电压 高阻接地故障 

分 类 号：TM862[电气工程—高电压与绝缘技术]