A Novel Shannon distance based pilot protection for grid-forming photovoltaic transmission line

When a fault occurs in grid-forming photovoltaic transmission lines, low-voltage ride-through control and virtual impedance mechanisms introduce significant differences in fault behavior compared to traditional synchronous machines, adversely affecting the performance of existing protection schemes, particularly their accuracy and responsiveness. To address this issue, this paper analyzes the fault characteristics of photovoltaic transmission lines under grid-forming control and evaluates the adaptability of traditional differential protection methods. A novel Shannon distance-based pilot protection scheme is therefore proposed. The method discretizes post-fault current sampling values into interval distributions and employs the Novel Shannon distance algorithm to quantify the similarity between distributions from both ends of the line. By analyzing the resulting similarity metric, the scheme effectively differentiates between internal and external faults, significantly improving upon conventional waveform similarity-based approaches. This enhances the reliability and robustness of protection under diverse fault conditions, including varying fault types, transition resistances, noise levels, and photovoltaic output variations. Simulation and hardware-in-the-loop test results confirm the validity and engineering feasibility of the proposed method. Compared with other similarity-based protection schemes, it demonstrates superior fault identification capability and higher reliability, particularly in scenarios where traditional methods suffer from reduced sensitivity or misoperation. The approach offers a promising solution for reliable protection in inverter-dominated power systems.