特高压长线路距离保护算法改进

特高压长距离输电线路呈显著的分布参数特性，其电容电流很大。分析表明，线路末端三相故障时，线路首端的测量阻抗不与故障距离成正比。研究指出，相间距离保护的测量阻抗与故障距离呈双曲正切函数关系，而传统接地距离保护应用于特高压长线路时存在原理性缺陷。理论分析并推导了新的接地距离元件测量阻抗的计算表达式，并提出了距离保护的改进措施，大量仿真证明了改进措施在特高压长线路上应用的正确性与有效性。

Improvement of Distance Protection Algorithm of UHV Long Transmission Line

UHV long transmission line is of its distinct characteristics of distributed parameters and large capacitive currents. The analysis shows that the measured impedance at the head of the line is not proportional to the fault distance when a three-phase fault occurs at the end of the line. Studies indicate that the relationship between the measured impedance and fault distance for phase-to-phase fault is a hyperbolic tangential function. The traditional distance protection for grounding faults has inherent defect when used in UHV long transmission line. This paper analyzes and deduces a novel calculation formula of distance protection for grounding faults, and proposes an improved method for distance protection. Simulation results have confirmed the validity and reliability of the proposed method in UHV long transmission line.