基于扩展边界的柔性直流输电网区域纵联保护  

Regional Pilot Protection for Flexible HVDC Grid Based on Extended Boundary

作　　者：薛士敏[1] 张君婷 李博通[1] 李翔宇[1] XUE Shimin;ZHANG Junting;LI Botong;LI Xiangyu(Key Laboratory of Smart Grid of Ministry of Education(Tianjin University),Tianjin 300072,China)

机构地区：[1]智能电网教育部重点实验室(天津大学),天津300072

出　　处：《高电压技术》2024年第12期5468-5481,I0006-I0008,共17页High Voltage Engineering

基　　金：国家电网有限公司总部管理科技项目(5500-202199270A-0-0-00)。

摘　　要：直流保护是保证多端柔性直流输电网安全的关键。行波保护动作速度快,可满足现有柔直电网对保护速动性的要求,但存在采样频率较高、可靠性不足、在线路边界受限时灵敏性较低的问题。针对上述问题,充分利用换流站及其各出线上的平波电抗器组成扩展边界,提出新型区域纵联方向保护原理。首先,分析扩展边界两侧电压的故障特征,利用扩展边界对电压时域波形的显著衰减形成的正反方向不同的故障特征来构造方向元件,构成纵联方向保护。该保护原理同时具备母线故障判别能力,并与相邻保护协调配合形成区域保护方案。其次,分析行波多次折反射过程对方向元件的影响,并给出保护动作时间。最后,进行仿真分析和对比验证。所提保护原理对采样频率要求低,在高阻故障、强噪声以及边界特性削弱时仍具有较高的灵敏性和可靠性。DC protection is essential for the safety of multi-terminal DC(MTDC)transmission grid.Traveling wave protection is fast enough to satisfy the speed requirement of DC protection,however,has defects of high sampling rate,low reliability and low sensibility when line boundary is limited.In this paper,the new regional directional pilot protec-tion scheme is proposed,in which extended boundaries consisting of the converter and the reactors at each line of converter are used.Firstly,the fault characteristics of voltage on both sides of extended boundaries are analyzed.The dif-ferent fault characteristics between backward and forward faults caused by the obviously attenuation characteristics of extended boundaries on voltage time domain waveform are used to realize the fault identification,in which the directional pilot protection is developed.Busbar fault identification can also be realized.In addition,a regional protection scheme is formed by coordination between adjacent protections.Then the influence of multiple reflected and refracted traveling wave on the fault characteristic is analyzed,and the protection operation time is settled.Finally,simulations and compar-isons are performed.The proposed scheme has a characteristic of low requirements for sampling rate,and has a high sensibility and reliability under large fault resistance,strong noise,and relatively low reactor.

关 键 词：多端柔性直流输电网 扩展边界 故障行波分析 故障方向识别 区域保护 方向纵联保护 

分 类 号：TM721.1[电气工程—电力系统及自动化] TM773