Abstract: Small-section conductors erected on the same tower in the power grid are gradually unable to meet the verification requirements of the N-1 or N-2 criterion. Traditional solutions include capacity-increasing renovation with Invar core conductors and demolition & reconstruction of large-section transmission lines, which suffer from high construction cost and investment waste.The scheme of converting parallel lines on the same tower into a single-circuit line and constructing a new large-section line separately can not only form two non-same-tower large-section lines, but also save 220 kV bays on both sides. By addressing the technical difficulties of the parallel line reconstruction scheme, analyzing its impact on power grid operation, and proposing corresponding protection and control strategies, this paper puts forward a capacity expansion scheme of converting same-tower parallel lines to single-circuit lines. Arranging additional parallel lines in the middle section is adopted to improve the accuracy of relay protection and break the transmission bottleneck of existing small-section same-tower conductors.The proposed idea provides a novel method for power grid upgrading and renovation, and satisfies the full-life-cycle development requirements of transmission lines.