输电线路功率型行波纵联保护新方法

为提高纵联保护的灵敏性与可靠性,提出一种行波功率型的纵联保护新算法。该算法利用彼得逊等值模型,分析线路区内、区外故障时的初始行波分布特征,给出了初始行波无功功率定义。基于S变换提取单频率的初始电压、电流行波,计算出初始行波无功功率,根据线路两端的初始行波无功功率幅值之比构成保护判据。当被保护线路区外故障时,线路近故障点端几乎测量不到初始行波无功功率,而远故障点端测量到的初始行波无功功率数值较大;被保护线路内部故障时,线路两端均存在较大的初始行波无功功率。根据线路两端测量的初始行波无功功率相对大小关系,能够明显地区分出线路内外部故障。理论分析和PSCAD/EMTDC仿真结果表明,该保护性能可靠性高、动作速度快、动作门槛值整定简单、计算量小;在小故障初始角下仍能准确识别区内外故障,且不受故障类型、故障位置、过渡电阻和母线结构等因素影响。

A New Pilot Protection Algorithm Based on Traveling Wave Power for Transmission Lines

To improve the reliability and sensitivity of traveling wave pilot protection, a new algorithm of pilot protection based on traveling wave power for transmission lines is proposed. The algorithm uses Peterson equivalent model to analyze the distribution characteristics of initial traveling wave at fault lines, and the definition of initial traveling wave reactive power is given. The initial traveling waves of single frequency are obtained by S transform to calculate the initial traveling wave reactive power, and the ratio of initial traveling wave reactive power at both ends of transmission line is used to make the protection judgment. For the external fault, there is little initial traveling wave reactive power at the end of the protected line near the fault point, but reactive power is great at the end far from the fault point. For the internal fault, the initial traveling wave reactive power is great at both ends of the protected line. Then the internal and external fault of transmission lines can be identified obviously based on the relative value of the initial traveling wave reactive power at both ends. Theoretical analysis and simulation on PSCAD/EMTDC show that the proposed method has higher reliability, faster action less calculation and simply set action threshold value, and the internal and external fault can still be distinguished accurately under the condition of smaller fault inception angle by the presented method, while its performance is not affected by fault types, fault location, grounding resistance and bus configuration.