直流输电线路单极故障不平衡电流分析及差动保护改进方案  

Analysis of single-pole fault unbalanced current and improvement of a differential protection scheme for HVDC transmission lines

作　　者：褚旭 孙锦琛 CHU Xu;SUN Jinchen(National Electric Power Conversion and Control Engineering Technology Research Center(Hunan University),Changsha 410082,China)

机构地区：[1]国家电能变换与控制工程技术研究中心(湖南大学),湖南长沙410082

出　　处：《电力系统保护与控制》2021年第2期47-56,共10页Power System Protection and Control

基　　金：国家自然科学基金资助项目(51807053);湖南省自然科学基金资助项目(2020JJ5056);中央高校基本业务费资助项目(531107051113);国家重点研发计划资助项目(2018YFB0904600)。

摘　　要：电流差动保护基于基尔霍夫电流定律,其从原理上具有绝对的选择性。但随着输电距离日益增加、线路分布特征愈加显著,传统电流差动保护需要增长延时、提高门槛以避免故障暂态分布电容电流引起的误动,降低了保护速动性、灵敏度。为了解决上述问题,研究了利用线路补偿点计算电流的差动保护改进判据,对由线路参数耦合特性引入的健全极不平衡电流的产生机理进行理论分析及仿真验证,提出了基于分布参数模型利用多补偿点计算电流的高压直流输电线路差动保护方案。所提出差动保护方案不受输电线路参数分布特性、耦合特性的影响,能够在故障全过程投入,实现直流线路分极保护,保护灵敏度高。多种故障情况下数字仿真结果及与传统差动保护的对比仿真验证结果,均表明了所提出差动保护原理的可行性及有效性。Based on Kirchhoff's law,current differential protection can protect a transmission line with superior selectivity.The influence of the parameter distribution characteristic increases with the length of the transmission line.The differential current protection scheme presently being used for an HVDC transmission line has to increase the time delay and protection threshold to avoid mis-operation induced by distributed capacitor current along the line,which leads to low operational speed and sensitivity.To solve these issues,an improved differential protection criterion using the calculated current at a compensation point of the transmission line is studied.The mechanisms which produce its unbalanced current induced by the coupling characteristic are analyzed and simulated.Based on the distributed parameter model,a current differential protection algorithm using the compensation current of multiple points is presented for HVDC transmission lines.The proposed algorithm is independent of the parameter characteristics of the transmission line and can split-pole operate during the fault transient process with high sensitivity.Its feasibility and validity are verified based on the simulation results and comparative results of a variety of fault scenarios.

关 键 词：高压直流输电线路 差动保护 分布特性 耦合特性 不平衡电流 

分 类 号：TM773[电气工程—电力系统及自动化]