为了解决高压直流输电线路保护易受雷击干扰影响的问题，提出了一种基于多重分形谱二次多项式拟合的直流输电线路雷击干扰与故障识别的新方法，这是首次将多重分形谱算法应用于区分雷击和区内故障。该方法通过计算电压暂态信号的多重分形谱，并利用其二次多项式拟合函数的最高次项系数来表征电压信号的波动程度，从而实现对雷击干扰与故障情况的辨识。仿真结果显示，该方法不仅能准确识别雷击干扰和故障，而且识别速度快。此外，多项式拟合系数能够更好地表征不同信号的波动差异。因此，该方法可作为高压直流输电线路保护的一种辅助判据，对于进一步提高高压直流输电线路保护的可靠性具有重要意义。

In order to solve the problem that the protection of high voltage direct current （DC） transmission lines is susceptible to lightning interferences, a new method for the identification of lightning interferences and faults on DC transmission lines based on the quadratic polynomial fitting of the multifractal spectrum is proposed, which is the first time that the multifractal algorithm is applied to distinguish between lightning strikes and in-area faults. The method achieves the identification of lightning interference and fault conditions by calculating the multifractal spectrum of the voltage transient signals and using the coefficients of the highest terms of its quadratic polynomial fitting function to characterise fluctuation of the voltage signals. Simulation results show that the method can not only accurately identify lightning interferences and faults, but also identify them quickly. In addition, the polynomial fitting coefficients can better characterise the fluctuation differences of different signals. Therefore, the method can be used as an auxiliary criterion for high voltage DC transmission lines protection, which is of great significance for further improving the reliability of DC transmission lines protection.