基于线模前行波平均变化率的多端柔性直流线路单端方向保护OA

In multi-terminal flexible DC transmission lines with T-connection,the boundaries of T zone are not clearly defined and the line boundaries are asymmetrical,making it extremely challenging to accurately identify faults on both sides of T zone.To address the issue of fault location identification in multi-terminal flexible DC transmission lines,this paper proposes a single-end direction protection scheme based on the average change rate of line mode forward travelling waves.First,the propagation characteristics of the line mode forward travelling wave are analyzed when faults occur on the left side of T zone,the right side of T zone,inside T zone and outside the converter station area.Analytical expressions for the line mode forward travelling wave at different fault locations are derived,revealing the trends in the waveform characteristics of the line mode forward travelling wave as it passes through the protection devices on both sides of T zone under different fault conditions.Second,the average rate of change of the line mode traveling wave measured by the protection devices on both sides of T zone is calculated,and criteria for distinguishing for faults on the left side of T zone,the right side of T zone,inside T zone,and outside the converter station area are proposed.Based on this,a single-ended direction protection scheme for multi-terminal flexible DC transmission lines based on the average rate of change of the line mode traveling wave is proposed.Finally,extensive simulations demonstrate that this scheme can accurately identify the fault location and achieve full-line fast protection for multi-terminal flexible DC transmission lines.