Modelling the Structural-Dynamics of Electrical Overhead Line Power Conductors
As a general definition, the presence of any repeated motion after a regular interval of time is known as vibrations. The basic theory of vibrations is described by the system of forces acting on a moveable and deformable body. The natural phenomena existing in the universe such as earthquakes, water waves (i.e., tidal), sound or noise (i.e., Aeolian tone), and light are the result of transmitted waves that are described by propagating vibrations in space. The characteristics of vibrations are usually quantified by measuring the resultant vibration wave amplitude, frequency, velocity, and wavelength. Moreover, the medium of vibration has a significant impact on the mechanism of the structural vibration motion, which depends on the fluid properties and impacted structure geometry.
One of the main assets in electrical power systems is Overhead Lines (OHLs), which are placed outdoors and exposed to various environmental conditions. The most common OHLs wind-induced structural motion is Aeolian conductor vibrations. The solid beam theory is merely implemented to model OHL conductors to predict their vibration response, based on the assumption of homogenized properties. Therefore, two models are considered in this paper:
- Computing wind-conductor interaction.
- Evaluating the Free Vibration of the conductor's real design.
Computational Fluid Dynamics (CFD) and Structural Mechanics associated with existing COMSOL Multiphysics® numerical capabilities are a power tool to solve fluid-structure interactions (FSI) and bending response of complex structures. The physical phenomenon considered in this paper is Aeolian Conductor Vibration which implicates the flow of air across high-voltage OHL conductors, which induces Aerodynamic Forces through the vortex-shedding on the conductor's wake. To model this phenomenon, the structural dynamics of FSI are reviewed in the case of OHLs, to compute the Aerodynamic Forces acting on the OHL conductor. The best application found to assist in building this model is the Fluid-Structure Interaction example found in COMSOL® built-in application library.
On a different study, the free vibrations analysis of the homogeneous and real conductor design is performed to determine the importance of considering the layer-to-layer interaction (using identity/Contact Pairs) and Material Properties as it is the case for OHL conductors. This is achieved by performing free vibration analysis using Structural Mechanics physics of the 3-D model by making use of the vibration Analysis of a Deep Beam example which is found in the application library. The same model is used to analyse the vibration of the real design of OHL conductor geometries and compares the use of Beam and Solid Mechanics interfaces.
The simulation results of the Aerodynamic Forces and Free Vibration Analysis showed good corroboration with the reported experimental data. The complex structure model greatly captured the interaction of conductor layers, which is evidence of the necessity of considering the complex structure of OHL conductors when evaluating their electro-mechanical response. The simulations time and accuracy are highly dependent on the computation capabilities of the utilized computing resources.
