摘要
换流变压器是连接交流系统和直流系统的枢纽,对系统安全运行有着重要影响。由于其直接和换流器相连,阀的单向导通性对换流变压器差动保护的选择性造成了严重影响,可能导致换流变压器在区内故障时二次谐波占比超过15%,使差动保护误闭锁。该文基于故障后阀的通断情况研究了逆变侧换流变压器发生阀侧绕组末端单相接地故障后的等值电路,分析了差动保护误闭锁的原因。依据换流变压器阀侧三相电流和的特征,提出一种防止单相接地故障时差动保护误闭锁的方案。理论分析和仿真结果表明采用该方案的差动保护在阀侧绕组末端单相接地时能可靠动作,在励磁涌流发生时能可靠闭锁。
As the key link between alternating current system and direct current system,a converter transformer plays a very vital role on the safe operation of the HVDC system.Because it is directly connected to the converter,the single guide compatibility of the valve has a severe impact on the selectivity of the differential protection of the converter transformer.As a result,a mal-blocking of the differential protection may occur during the regional fault when the proportion of the second harmonic exceeds 15%in differential current.In this paper,the equivalent circuit of the inverter side converter transformer is studied based on the on-off characteristic of the valve after a single-phase grounding fault at the end of the valve side winding.Furthermore,the causes of the mal-blocking of the differential protection are analyzed.Based on the characteristics of the sum of the valve side three-phase current of the converter transformer,a novel solution is proposed to prevent the mal-blocking of the differential protection at a single-phase grounding fault.The theoretical analysis and the simulation results show that the differential protection applying this solution can trip reliably when a single-phase grounding fault occurs at the valve side and can block reliably when a magnetizing inrush occurs.
作者
张艳霞
张富贺
卢静怡
毕安露
ZHANG Yanxia;ZHANG Fuhe;LU Jingyi;BI Anlu(Key Laboratory of Smart Grid of Ministry of Education(Tianjin University),Nankai District,Tianjin 300072,China)
出处
《电网技术》
EI
CSCD
北大核心
2021年第6期2388-2395,共8页
Power System Technology
关键词
换流变压器
差动保护
阀侧故障
单相接地误闭锁
converter transformer
differential protection
fault at the valve side
mal-blocking on single-phase grounding
