Structural form improvement of steel narrow-based lattice supports for high-reliability overhead lines

Introduction. The development of electric networks directly depends on cost and reliability of overhead line structures, which requires, first of all, clarification of static and dynamic loads and impacts in order to assess the bearing capacity during design and operation; search, development and testing of new optimal solutions for overhead line supports, as well as well as an integrated approach to network design as single structural system based on requirements for manufacturing, installation and operation. The purpose of work is to find the optimal structural form of steel narrow-base tower and portal supports for 35 and 110 kV overhead lines.

Materials and methods. When studying tower single and portal supports of 35 and 110 kV overhead power lines with diagonals and spacers by weight, normal, emergency and installation modes of operation were taken into account for anchored sections with overhead line rotation angles from 0 to 60°. The line was considered as single system. When studying anchor-angle supports by weight, possible operating modes were taken into account: normal, emergency and installation for different rotation angles of line route.

Results. Has been developed an algorithm for determining voltages for all operating modes of current-carrying wires and required number of overhead power line spans regulated by regulatory documents. For the first time has been solved the problem of calculating the stress-strain state for overhead power line as single system, taking into account the joint operation of current-carrying wires, ground wires, insulator strings, supports and foundations. Based on proposed numerical optimization method mass and cost of narrow-base supports have been further reduced by up to 20 %.

Conclusions. Proposed narrow-base supports are technologically advanced in manufacturing, installation and operation. Portal supports with and without reinforcing diagonals are rational in anchor-angle versions of 110 kV, especially with large loads from plane and significant differences in terrain, as well as in intermediate versions of 110 kV with support height of up to 27 m. On 35 kV overhead lines the use of portal free-standing supports gives a positive effect only for intermediate versions up to 20 m high.

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