Numerical computation of the overhead power lines electric field intensity
Abstract
Overhead power lines are sources of low-frequency electromagnetic fields, and their limit levels are prescribed in the currently valid Ordinance on Protection from Electromagnetic Fields (NN 146/14). Various numerical models and software packages for calculating the electric field strength and magnetic induction of all low-frequency sources are based on Maxwell’s equations. This paper describes a 3D quasi-static electromagnetic model for calculating the electric field strength of overhead power lines based on the finite element technique. The actual shape of the catenary formed by the phase conductors and protective ropes is approximated by an arbitrary number of flat thin-wire cylindrical segments of active and passive conductors. In order to obtain the most accurate results of the distribution of the linear charge density along the catenary, segmentation was performed separately for each span of the overhead power line. In addition, it is known that metal poles of overhead power lines distort the electric field and can significantly reduce its value, but their influence is often neglected in numerical calculations. Here they are taken into account by approximating them using segments of cylindrical conductors of zero potential. A system of linear equations for calculating the charge density distribution was obtained from the matrix of the eigen and mutual coefficients of all coupled components of the quasi-static electromagnetic model. By solving the global system of linear equations, the distribution of the scalar electric potential and the electric field strength at selected points in the air was calculated. In a numerical example, the distribution of the electric field strength near a metal pole of an overhead power line was calculated. In the vicinity of the pole, noticeable deviations were obtained between the calculated electric field strengths with the influence of the pole taken into account and the calculation with the influence of the pole neglected, which indicates that the influence of the poles on the distribution of the electric field strength should be taken into account.
Tonći Modrić
Associate Professor | Department of Electrical Intallations and Systems
Researcher and Full Professor at the Faculty of Electrical Engineering, Mechanical Engineering, and Naval Architecture in Split. His research focus is numerical modeling and calculation of the electric and magnetic fields in power systems and transmission lines, with an emphasis on the development of advanced models for interpreting geoelectrical ground survey data. Additionally, he is involved in the analysis of electromagnetic transients in systems with a high share of renewable energy sources, using finite element techniques.
Slavko Vujević
Professor Emeritus
An expert in electrical engineering, particularly known for his contributions to numerical modeling of electromagnetic phenomena, lightning protection, and grounding. Throughout his career, he was a key member of the Faculty of Electrical Engineering, Mechanical Engineering, and Naval Architecture in Split, where he taught, mentored students, and actively participated in scientific research and international professional organizations.