Danil Aleksandrovich Yaroslavsky et al., International Journal of Emerging Trends in Engineering Research, 8(6), June 2020, 2663 - 2667 2663 ABSTRACT This article is devoted to the importance of inspection of overhead power lines by detection of mechanical loads on conductors. A conductor under the action of forces caused by wind pressure swings like a pendulum. It is possible to determine conductor oscillations in space by inclinometer with high precision. While reconstructing conductor geometry in overhead power line span, it is possible to determine mechanical loads. Mechanical loads of overhead power line conductor are estimated using the developed model of free harmonic oscillations in span. The mathematical model of conductor is based on mathematical models of ideal cable and physical pendulum. Conductor is a physical pendulum, where a conductor acts as body, and fixed axle is presented by direct line passing through the conductor suspension points. The developed model determines conductor sag by oscillation period of conductor in span. The article discusses calculation algorithm of conductor sag for two cases: the conductor suspension points are at one height; the conductor suspension points are at different heights. Theoretical calculation is performed for the model of overhead power line span accompanied by estimation of sensitivity of the developed model and its error upon determination of conductor sag. Using the conductor sag, it is possible to reconstruct its geometry, thus, the mechanical loads of conductor. On the basis of initial geometrical parameters of overhead line span, it is possible to inspect its current state. Key words: overhead power line, monitoring of overhead lines, sag, conductor oscillations, mechanical loads, conductor. 1. INTRODUCTION Global energy market will grow up to 2035 due to increase in demand for energy in developing countries (being determined by growing industrialization and urbanization of Asian and African regions as well as population increase) [1]. Energy is transferred from power stations or substations to consumer by overhead power lines (OPL). Total distance of OPL in Russia exceeds 2.8 million kilometers. Electrical grid facilities are getting outdated. The equipment wear reaches 70% [2]. However, due to increased demand for energy and implementation of new OPL segments, it becomes necessary to perform their complete inspection aiming at improvement of their operation. OPL structural elements experience both horizontal (for instance, mechanical stresses in stringed wire/cable), and vertical loads (for instance, under own weight or under weight of wire/cable). Wires and cables are the elements of OPL, which most obviously exhibit variations of mechanical loads due to variation of wire/cable tension as a function of temperature and formation of ice deposits [3], as well as oscillations under wind blasts. When mechanical load exceeds ultimate strength of OPL element, it can be damaged: breakage of conductor/cable, destruction or breakdown of isolator, phase fault due to swinging of conductors, etc. Mechanical loads of OPL conductors are mainly estimated by two methods: direct measurements (by strain gauges) [4, 5, 6] or indirect ones (inclinometry based on determination of conductor inclination angle using accelerometers) [7, 8, 9, 10]. In addition to numerous advantages, the weighing method is characterized by certain disadvantages, namely: necessity to modify line accessories and high costs [11]; unavailability of detection systems for OPL with the voltage of 35 kV and below. In its turn, inclinometry is a reliable and straight method, it does not require to modify OPL design, though, it has measurement errors of inclination angle of sensor (accelerometer) and errors related with conversion of the inclination angle into conductor stringing force [7, 12]. Therefore, sufficiently precise localization of problematic segment of OPL or fault is required, since quite often travelling along OPL is difficult and the rate of fault elimination is directly related with incurred losses. Herewith, the quality improvement of OPL inspection should be accompanied by minimum expenses, that is, it is desirable to Studying the Model of Free Harmonic Oscillations of Overhead Power Lines Danil Aleksandrovich Yaroslavsky 1 , Van Vu Nguyen 1 , Marat Ferdinantovich Sadykov 1 , Mikhail Petrovich Goryachev 1 , Dmitry Alekseevich Ivanov 1 , Tatyana Gennadievna Galieva 1 , Yuliya Yurievna Vassunova 1 , Aleksandr Nikolaevich Tyurin 2 1 Kazan State Power Engineering University, Kazan, Russia 2 Kazan commissioning department of JSC "Tatelectromontazh", Russia ISSN 2347 - 3983 Volume 8. No. 6, June 2020 International Journal of Emerging Trends in Engineering Research Available Online at http://www.warse.org/IJETER/static/pdf/file/ijeter72862020.pdf https://doi.org/10.30534/ijeter/2020/72862020