A comprehensive decision line selection method based on optimizing transient zero sequence direction and improving the first half wave is proposed to address the issues of poor adaptability and low selection accuracy of existing criteria for small current grounding.Through the design of band-pass digital filters and analysis of transient first half wave characteristics,the first half wave short window,first half wavelength window,and sampling points with polarity satisfying characteristics within the band-pass filtering data window are comprehensively utilized to determine their respective correlation coefficients,form a comprehensive criterion for line selection.Based on this comprehensive decision-making method,a corresponding line selection protection device was developed,and RTDS dynamic simulation testing and real type testing were conducted.The results indicate that the line selection method can adapt to various system operation modes and fault conditions,verifying its effectiveness and reliability.
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