Journal of Engineering Research

When the Ta’e–Karamay 750 kV transmission line project is connected to the Tacheng Tuoli coal-fired power delivery project, the original breaking-in connection scheme is faced with problems such as high cost, high construction risks, and long power outage duration. This paper proposes an optimized design scheme using the permanent-temporary combination for single-circuit transmission lines. Taking the breaking point in the 20 mm heavy icing section of the project as the core research object, and in accordance with the design specifications for heavy icing transmission lines, the optimization is carried out in three dimensions: route selection, insulation coordination, and tower structure design. The connection route is optimized and the span is increased to reduce the corner angle. The clearance values are determined per industrial standards, and the cross-arms are lengthened to meet the current insulation requirements. The JC4120J guyed-type tower is adopted, and measures including torsional resistance checking, finite element simulation, structural reinforcement, and high-grade steel selection are implemented to resolve the issues of coordinated stress and torsion of the tower under short-term and long-term conditions. Comparative analysis shows that compared with the original scheme, the optimized scheme reduces the investment by about 880,000 yuan, lowers the construction risk level from Level II to Level III and below, and shortens the power grid outage duration from 13 days to less than 1 day. Meanwhile, it simplifies the construction process and reduces coordination difficulty. This permanent-temporary design realizes the overall planning of current construction and future connection, effectively avoids resource waste, and improves the economic efficiency, safety of project construction, and power supply reliability of the power grid. Its design concept and technical measures can provide important engineering references for breaking-in connection projects of EHV transmission lines under complex meteorological and geographical conditions.

Overhead transmission line; Permanent-temporary combination; Heavy icing section; Transmission tower design; Breaking-in connection; Torsional resistance design