Fréchet Distance Based Pilot Protection Method for Centralized Photovoltaic Station Transmission Lines

This paper proposes a pilot protection method based on the Fréchet distance to address the decline in performance of traditional pilot protection and the issues with existing similarity protection algorithms. The method overcomes problems such as insufficient waveform difference measurement, difficulty setting fixed values, and computational failure when the new energy is weak. Additionally, the paper highlights the problem of adapting traditional differential protection and existing similarity algorithms. A proposed protection method integrates the fault current's amplitude and phase characteristics. The method combines spatial trajectory similarity with time-domain waveform correlation. It introduces the Fréchet distance as a quantitative index of the waveform difference metric. It constructs the mathematical connection between the Fréchet distance and the amplitude and phase differences of the time domain current waveform. This provides a theoretical basis for constant value rectification. Secondly, the algorithm's time complexity is optimized by incorporating dynamic programming ideas. The method is not affected by line capacitance current or new energy output characteristics, and it has superior sensitivity and reliability compared to existing protection principles. The results indicate that the proposed protection principle can accurately identify faults inside and outside the zone with a time window of only 10ms. The fastest action speed can be achieved in 1 ms or less, and the principle can withstand transition resistance and noise.