计及故障点两侧零序电流相位差的新能源送出线路接地故障时域距离保护研究

新能源电源故障电流呈现弱馈性、强受控性并具有大量的间谐波，导致现有工频量距离保护可靠性下降，而时域距离保护主要根据方程求解故障距离，受新能源短路电流特性影响较小。针对新能源送出线路较长时，线路分布电容对零序电流相位的影响不可忽略，进而导致故障距离的计算产生较大偏差的问题，提出了一种计及故障点两侧零序电流相位差的新能源送出线路时域距离保护改进方案。首先，计及故障点两侧零序电流相位差的影响，将过渡电阻等效为过渡阻抗。然后，通过列写故障回路方程并求解故障距离，形成保护判据。最后，基于PSCAD/EMTDC大量仿真实验，验证了所提时域距离保护方案计算故障距离的误差较小，可以较好地适用于新能源经中长距离交流线路送出的场景。

Time domain distance protection of new energy transmission line grounding fault considering the phase difference of zero sequence current on both sides of the fault point

The fault current in new energy power supply presents weak feedback, strong controllability and a large number of interharmonics. This leads to decline in the reliability of existing power frequency distance protection. Time-domain distance protection mainly establishes the fault distance based on the equation, and is less affected by the short-circuit current characteristics of new energy. This paper proposes an improved time domain distance protection scheme for new energy transmission lines that takes into account the phase difference of zero sequence current on both sides of the fault point. This is to address the issue of significant deviation in the calculation of fault distance caused by the influence of distributed capacitance on the phase of zero sequence current when the new energy transmission line is long. First, taking into account the influence of the phase difference of the zero sequence current on both sides of the fault point, the transition resistance is equivalent to the transition impedance. Then, by writing the fault circuit equation and finding the fault distance, a protection criterion is formed. Finally, based on a large number of simulation experiments using PSCAD/EMTDC, it is verified that the time-domain distance protection scheme proposed in this paper has only a small error in calculating the fault distance, and can be well applied to scenarios where new energy is transmitted through medium to long distance AC lines.