Calculation method and experimental research on strand breakage in large cross-section conductors considering contact between strands

This paper proposes a numerical method for the strand breakage defect in large cross-section conductors during tension stringing construction. First, the contact types between strands in the same layer and adjacent layers of the conductor were analyzed. The relationship between the force and depth of strand contact was then determined. The structural calculation method for straight conductor under tensile and torsional loads was proposed considering in the contact between strands, which can obtain the accurate calculation results of strands in different layers. The method avoids the establishment of complex multi-strand models and the setup of large number contact pairs, and has a much higher computational efficiency than finite element method (FEM), the performance gap is up to 300 times. For 630 mm² conductor, the calculated results of strands demonstrated significant changes in the axial forces of strands of different layers under positive and negative torque, which substantially influences the strand breakage patterns. Through the analysis of the mechanical cause of strand breakage, a calculation formula for the axial force of strands were proposed based on the deformation process as the conductor passes through the stringing block. The results of 630 mm² conductor indicated that the torque and tension on the conductor are critical factors of the strand breakage. Referencing the actual engineering conditions, a test setup was designed to simulate the conductor passing through the block, and the breakage defect of strand was reproduced. The forms and locations of the breakage defects observed in the tests were consistent with the calculated results, validating the alignment of the theoretical analysis with actual states. This proposed method can be applied to analyze the strand defect of conductor with various cross-sections, which offers a theoretical foundation for the prevention and control of construction defect in the transmission line.