1 FINITE ELEMENT MODELLING OF AEOLIAN VIBRATIONS ON STRANDED HIGH-VOLTAGE OHL CONDUCTORS Mohammed A. AlAqil 1* , Konstantinos Kopsidas 2 1, 2 School of Electrical and Electronic Engineering, The University of Manchester, Manchester, UK *mohammedabdulaziz.alaqil@manchester.ac.uk Keywords: CONDUCTORS, AEOLIAN VIBRATIONS, FEM, COMSOL, STRANDING SHAPE Abstract The problem of Aeolian vibrations has been studied in indoor test-spans for many years. Its relevant standard experimentations have resulted in introducing the Energy Balance Method (EBM) which is the most commonly implemented method in the industry. Besides conductor properties, aerodynamic forces (Lift and Drag forces) acting on the conductor are the main input data for the EBM. The existing models frequently use experimental data of Lift and Drag forces for a cylinder. To further investigate the capabilities of wind-conductor interaction numerical modelling, it is useful to take advantage of Finite Element Modelling techniques. This paper simulates the wind flow around single OHL conductors with different outer layer stranding shapes and sizes utilizing COMSOL Multiphysics software. The simulations are based on solving the Navier- Stokes equation to compute the aerodynamic forces by integration of the pressure and shear forces within the boundaries of the conductor geometry. The numerical model computes the aerodynamic forces for three conductor geometries including smooth-surface, round-stranded, and trapezoidal stranding shapes. The numerically obtained solutions show that less aerodynamic forces are experienced by rounds and trapezoids compared to the cylinder geometry. This observation is true for high Reynolds numbers. 1 Introduction It is globally observed that electricity generation and consumption are increasing rapidly due to the integration of renewable resources and the electrification of energy resources to replace traditional fossil fuels. To accommodate this rapid demand increment, electric utilities intend to reinforce the power capacity of the electrical network by constructing new transmission overhead lines (OHLs) or re- conductoring using novel conductor designs such as High- Temperature Low-Sag (HTLS) technologies. OHLs are constructed outdoors in different environmental conditions and terrains which make them susceptible to various types of wind-induced motions that are experienced mostly by conductors. Mechanical vibrations constitute a significant distraction and may harm OHL conductors through fretting fatigue [1]. In general, wind-induced conductor motions can take the form of one of the following three categories: (i) Aeolian vibrations, (ii) galloping, and (iii) wake-induced oscillations. Aeolian vibration, the most commonly reported type, is generated due to wind-conductor interaction associated with vortex-shedding at conductor wake [2, 3]. The vast majority of experimental studies on Aeolian vibrations are conducted in costly indoor and outdoor test- spans with limited site access. The capabilities of advanced numerical modelling techniques are deemed to be a compelling alternative tool to replace the practical experimentations. The numerical methods would be worthwhile to identify the potential risks of vibrations on OHL conductors and overcome some of the limitations in standard calculation methods. The physical motions of OHL conductors are governed by the interaction of fluid dynamics, conductor dynamics, and efficiency of external damping system. Therefore, wind- conductor interaction is complicated. Conductor vibration performance is frequently described by non-linear algebraic equations resulting from mathematical models that are represented by the Energy Balance Method (EBM) [4, 5]. This method quantifies vibrations by re-scaling the conductor’s vibration mode shapes and balancing the wind power input to the conductor power dissipation characteristics (i.e., self-damping). The aerodynamic forces are the primary input data in the EBM. Typical experimentations to evaluate the aerodynamic forces of OHL conductors are typically carried out on smooth-surface cylinders, neglecting the effect of conductor outer and inner stranding shapes [6]. This paper describes the Aeolian vibration phenomenon and presents a Finite Element Modelling (FEM) approach to evaluate the aerodynamic forces for single OHL conductors. The FEM solution is based on solving the Navier-Stokes equation to compute the aerodynamic forces exerted on the conductor. The analyses are performed on smooth-surface conductor geometry and compared against round (RW) and trapezoidal (TW) stranding shapes. A summary of background knowledge and past modelling efforts are presented in section II. Moreover, the proposed FEM approach is detailed and implemented utilizing COMSOL Multiphysics software in section III and section IV,