Bojan Trkulja

Computation of Electric Fields Inside Large Substations

Calculation of electric field based on integral equations approach and suited to solving large-scale problems is presented. Integral equations are solved by appliance of BEM and Galerkin method. Unknown distribution of the surface charge density is approximated by bicubic splines, which ensure smooth approximation of sources. Accurate calculation of electric fields requires detailed modeling of power system equipment inside substations. This results in large models, which are solved by parallel computing. Numerical results are compared to measured fields inside a 400 kV substation. Comparison shows good agreement, thus approving applicability of the proposed approach in analysis of exposure to electromagnetic fields and electromagnetic compatibility.

Frequency dependent resistance calculation of multiple conductors

Purpose The purpose of this paper is to present a method for calculating frequency-dependent resistance when multiple current-carrying conductors are present. Design/methodology/approach Analytical and numerical formulations are presented. Both skin- and proximity-effects are considered in the numerical approach, whereas only skin-effect can be taken into account in analytical equations. The calculation is done using a self-developed integral equation-based field solver. The results are benchmarked using professional software based on the finite element method (FEM). Findings Results from the numerical approach are in agreement with FEM-based software throughout the whole frequency range. Analytical formulations yield unsatisfactory results in higher frequency range. When multiple conductors are mutually relatively close, the proximity-effect has an impact on effective resistance and has to be taken into account. Research limitations/implications The methodology is presented using axially symmetrical conductors. However, the same procedure can be developed for straight conductors as well. Practical implications Presented fast and stable procedure can be used in most electromagnetic devices when frequency-dependent resistance needs to be precisely determined. Originality/value The value of the presented numerical methodology lies in its ability to take both skin- and proximity-effects into account. As conductors are densely packed in most electromagnetic devices, both effects influence the effective resistance. The method can be easily implemented using a self-developed solver and yields satisfactory results.