# O. Kimstach, S.N. Novogretskiy, V.E. Milev. Span of overhead transmission lines

O. Kimstach

S. Novogretskiy

V. Milev

The calculation tasks of the span length of electrical transmission lines, which are constructed on the basis of ferroconcrete, composite, metal lattice and polyhedral transmission towers, using of approximating functions are considered. The span length is determined with the help of the continuous functions, which allows to search it for any combination of input data and to apply it in the algorithms of CAD of power supply systems.

The calculating problems of the overhead transmission lines span are analyzed. The design tasks of overhead transmission lines are given, in which the spanlength plays an important role. This indicates that the spanlength is the main parameter of overhead transmission lines. The purpose of the article is to determine approximately the span length by means of continuous functions. Calculation of the spanlength is performed based on the use of mechanical loads of conductors. The loads of the conductor weight, of the ice weight and of the wind pressure are considered. The spanlength is calculated in the presence of the most adverse climatic conditions, when all kinds of mechanical loads on the conductors are present. The tension of the conductors is also taken into account to ensure the permissible value of the conductor sag. The discrete coefficients of the mechanical loads of the conductors are approximated by means of continuous functions, which make it possible to considerably simplify the calculation of the span length and to apply the proposed method in the algorithms of computer-aided design of overhead transmission systems. The error of the applied functions of the approximation of the mechanical load coefficients tends to zero due to the selected functional dependencies. The final value of the span length is determined from two inequalities that limit the span length according to the conditions of the maximum permissible sag and the maximum mechanical load in the conductor under adverse climatic conditions. The first of the conditions has a simple mathematical form, so it can be solved analytically. The second condition is described by a complex mathematical relationship, which can be solved graphically or analytically using numerical procedures. As a normative basis for the algorithm development, the electrical installation code of Russia and Ukraine were used.

Conclusion: The proposed calculation algorithm makes it possible to determine approximately the span length of overhead lines by using a simplified procedure without the application of additional reference data; at the same time the approximating functions used have almost no errors, which allowingto predicate the high level of accuracy of the proposed algorithm.

Keywords: overhead transmission line, span, sag, approximation, continuous function.

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