Calculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations

Abstract

This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductors' configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. The alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is usually not analyzed in detail in undergraduate and even in graduate studies. For this purpose, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations.

Analysis of Capacitance to Ground Formulas for Different High-Voltage Electrodes

“…and h* = h + r. Table 7 shows the results obtained by applying Equations (11)-(13) and FEM, for different values of the radius r and the height h. Results presented in Table 7 show an excellent match between Equations (11), (13) and FEM results, although a greater difference when applying Equation (13), as expected.…”

“…Therefore, analytical solutions for capacitance only exist for a limited number of electrode geometries and configurations, which have almost no practical applications [11], and often only contemplate the stray capacitance to ground, thus disregarding the effects of nearby grounded electrodes, structures or walls [3].As a consequence, computational methods are increasingly being applied to solve such problem, although most of the published works deal with very particular problems, such as insulator strings [4,5,7], transformer windings [10] or voltage dividers [12], among others. FEM is perhaps the most applied computational technique to calculate the effects of capacitance, since it allows dealing with complex three-dimensional geometries, as reflected in several works [13][14][15][16][17][18][19].Since stray capacitances are not easily measurable, because of the low immunity to noise of the small signal to be acquired [20], results provided by numerical methods are a good alternative during the design stage of high-voltage devices and instruments. Therefore, the capacitance between energized electrodes or between electrodes and ground is a factor to be considered when designing and planning high-voltage projects and tests [11].Most works analyze specific problems related to the unwanted effects of stray capacitance, such as in transformer windings [10], motor windings [21] or insulator strings [7], among others.…”

“…As a consequence, computational methods are increasingly being applied to solve such problem, although most of the published works deal with very particular problems, such as insulator strings [4,5,7], transformer windings [10] or voltage dividers [12], among others. FEM is perhaps the most applied computational technique to calculate the effects of capacitance, since it allows dealing with complex three-dimensional geometries, as reflected in several works [13][14][15][16][17][18][19].…”

Study on AC Resistance of Layering Enamelled Stranded Conductor

“…Since the AC resistance data is more abstract, the current distribution in the conductor can be simulated and analyzed by finite element simulation method, which can directly compare the current distribution differences. It is also widely used in the simulation of various physical processes, such as current distribution in conductors, electric field distribution in insulation [12], etc.…”

Analysis of formulas to calculate the AC resistance of different conductors’ configurations

“…It is well-known that although the current density distribution in homogeneous conductors supplied with direct current (DC) is uniform, when dealing with conductors under alternating current (AC) supply, their current density is often not uniform throughout the cross-section because of the skin and proximity effects [1,2,3]. At high frequencies the current tends to be concentrated towards the periphery of the conductor [4], thus increasing the AC resistance and power loss in the conductor [5].…”