行波差动保护不平衡差流分析及实用方案

行波差动保护从原理上消除电容电流的影响,在超(特)高压远距离输电线路保护中具有突出的优势.然而行波差动保护在应用时,即使线路内部无故障也会产生一定的不平衡差流.从理论上分析了不平衡差流的4方面来源及其影响因素,即线路电阻模型误差、插值截断误差、两侧数据同步对时误差及空模分量与地模分量波速不一致等因素,提出了一种行波差动保护的实用方案,并对滤波技术及采样率进行分析.仿真验证表明,该方案灵敏度高,动作速度快,选相跳闸能力强,具有良好的应用前景.

Analysis and Application of Unbalanced Differential Current in Traveling-wave Differential Protection

Traveling-wave differential protection has a special advantage in EHV/UHV transmission line protection for its immune ability to distributed capacitive current.However,unbalanced differential current can occur at normal conditions when traveling-wave differential protection is applied.In this papers,four main factors affecting unbalanced differential current are investigated theoretically.They are line resistance model error,interpolated truncation error,data synchronization error and unequal traveling speed between earth sequence and spatial sequence.An applied scheme for traveling-wave differential protection is also proposed in the paper.The filtering algorithm and sampling rate in application are also discussed.EMTP simulation results show that the proposed scheme operates sensitively,rapidly and selectively,demonstrating good potential in field applications.