MECHANICAL CALCULATION OF FLEXIBLE WIRES WHEN THE CONCENTRATED FORCES ARE REPLACED BY A DISTRIBUTED LOAD

Abstract

The objective of mechanical calculation of flexible wires of substations and overhead lines is to determine the sag and tension in different climatic conditions. A wire with a uniformly distributed load is considered as a homogeneous flexible thread having the form of a parabola. Concentrated loads from spacers, barrier balls, stubs, taps to electrical apparatus and other elements are replaced with the one distributed over the span. On behalf of a span without tension springs of insulators the action of concentrated loads on the wire is considered, an error is determined when replacing the concentrated forces with the one uniformly distributed along the span by the load. The sag for the equivalent wire is determined with the aid of the ratio of the increase of the sag, due to the presence of concentrated forces. An equation of state has been drawn up which makes it possible to determine the tension after changing the number of concentrated loads, e.g., after installing spacers, hanging the barrier balls, fixing the taps. The dependence of the maximum sag on the number of concentrated forces is given. The definition of the coefficient of concentrated forces as the ratio of the sum of the concentrated loads to the weight of the wire in the span is presented. A relationship between the load factors, the increase of the sag and the coefficient of concentrated forces is established. The formula has been deduced for determining the error in the replacement of concentrated forces by a uniformly distributed load along the span as a function of the number of concentrated forces and the coefficient of concentrated forces. A decrease in the error with an increase in the number of concentrated forces has been demonstrated. A more accurate calculation of mechanical tensions and sag is possible with the use of a vector-parametric method for calculating the flexible busbar of substations and air-line wires, where the design model of wires in the form of a flexible elastic thread is placed, taking into account the spatial disposition of all structural elements.

Keywords

• стрела провеса, тяжение, гибкая нить, цепная линия, парабола, уравнение состояния, пролет, эквивалентный провод, коэффициент нагрузки