和应涌流导致直流闭锁极保护误动作分析

Analysis of DC Blocked Pole Protection Misoperation Caused by Sympathetic Inrush Current

2012年4月16日,高坡换流站极2换流变压器充电产生的和应涌流导致处于闭锁状态的极1换流器桥差保护2段(87CBY-2)误动作,极1由闭锁状态退至备用状态。文中对该事件中的保护动作情况进行了分析。从磁链的角度对和应涌流产生的机理、特点及影响其大小的因素进行了研究。从合闸相位角的角度对三相和应涌流方向不一致的现象进行了分析。提出和应涌流的产生及和应涌流中衰减很慢的非周期分量导致换流变压器的电流互感器严重饱和,是造成87CBY-2误动作的原因。利用PSCAD/EMTDC软件对和应涌流及三相和应涌流方向不一致进行了仿真,得到跟理论分析一致的结果。针对和应涌流对直流系统保护的影响提出了相应措施,并通过高肇直流RTDS仿真系统得到验证,对直流输电工程的实施及安全稳定运行有一定的参考价值。

On April 16th,2012,in Gaopo converter station,the sympathetic inrush current emerged when pole 2 converter transformers were charged lead the blocked pole 1 bridge differential protection stage 2（87CBY-2） misoperation,pole 1 turned to standby state from blocked state.This protection misoperation incident is analyzed.The mechanism on how the sympathetic inrush current was generated is studied from the point of view of the flux.The characteristics of the sympathetic inrush current and the factors that affect the size of the sympathetic inrush current are studied too.The phenomenon that the directions of three-phase sympathetic inrush currents are inconsistent is analyzed through the closing phase angle.The generation of sympathetic inrush current and the serious saturation of converter transformer（CT） caused by the aperiodic component of sympathetic inrush current that decays slowly are the reasons of the bridge differential protection malfunction.The sympathetic inrush current and the phenomenon that the directions of three-phase sympathetic inrush currents are inconsistent are simulated using PSCAD/EMTDC simulation software.Consistent results are obtained which matched the theoretical analysis.For the affect that the sympathetic inrush current impacts on high voltage direct current（HVDC） system protection,corresponding measures are proposed and verified by the Gao-Zhao DC real-time simulation system（RTDS）.The findings of this research provide valuable reference for the DC transmission project implementation as well as its security and stability enhancement.