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This paper investigates the impact of transmission line parameter calculation formulations on surge arrester performance in response to lightning strikes. This evaluation consists of comparing power and energy dissipated in surge arresters, as well as critical currents and line backflashover rates. The lightning performance of surge arrester installed in a typical Brazilian 138 kV transmission line is assessed by simulations in ATP software, while transmission line parameters are calculated in 3 different ways, namely: (i) Carson formulation, (ii) Nakagawa formulation considering the electrical parameters of the ground constant with the frequency, and (iii) Nakagawa formulation considering the frequency-dependent characteristics of the soil. Taking as reference the results determined by Carson's formulation (since this formulation is the most used in programs for calculating transients, such as ATP), it is shown that Nakagawa's formulations considering both constant and frequency-dependent soil parameters can lead to differences for the cases of unprotected lines, partially protected (lightning arresters in one or two phases) and fully protected (lightning arresters in all phases), resulting in an inaccurate prevision of insulation failure, leading to an increase in the backflashover rate. [ABSTRACT FROM AUTHOR]

The electric and magnetic fields generated by transmission lines, at ground level, must be carefully analyzed to ensure low levels of induced voltage in surrounded metallic elements. Additionally, whenever possible, one main concern on transmission lines projects should be improving maximum line power transfer capability. Thus, this paper aims to present multi-objective optimization studies applied to improve the use of overhead transmission lines by conductor rearrangement. As objectives of the optimization problem are considered the maximization of line power transfer capability and the minimization of resulting electric and magnetic fields at ground level. An efficient multi-objective evolutionary algorithm method is updated and used as a result of the technical conflicts inherent to the physical process. Symmetry strategies for the overhead transmission line geometric configuration are considered in the optimization process. The results illustrate the robustness and physical consistency of the adopted methodology. According to results, verified from real overhead transmission lines, one of the cases studies showed that by rearranging the conductors, it is possible to obtain, simultaneously, an improvement of 17.5% in the maximum line power transfer capability with a reduction of 31.8% and 32.8%, respectively, of electric and magnetic fields. [ABSTRACT FROM AUTHOR]

The method of moments (MoM) is widely used in several areas of knowledge to solve integral equations. In the specific case of solving electrical grounding transient behavior problems, the computational time is usually high. This paper presents new alternative solutions for solving the double integrals in the well-known hybrid electromagnetic model (HEM) applied to horizontal grounding electrodes. These new alternative solutions correspond to using an approximation to the exponential term appearing in the finite integral needed to obtain the parameters. Two approaches are considered either using Maclaurin series or Padé approximation. The corresponding results are compared with those obtained by using HEM with MoM. It is shown that the proposed solutions allow reducing the computational time, without jeopardizing accuracy. [ABSTRACT FROM AUTHOR]