engleski

Improved numerical calculations of grounding system parameters in non-equipotential AC substation grouding grids

This paper presents a more accurate mathematical modelling of the non-equipotential large grounding system at power frequency, which includes transversal mutual conductances between grounding segments as well as longitudinal mutual impedances. Numerical calculation of the grounding current field is based on the point collocation method with current density approximation by the second-degree polynomials and two-layer soll model. The method of images is used for solving the boundary value problem. Using the direct solution of a system of linear equations (matrix inversion), unknown coefficients of the current density approximation along all grounding elements and unknown potential values at nodal and collocation points are obtained. Such accurate modelling also enables more accurate computation of the grounding impedance. This procedure is applied in determining the inductance of the rectangular grids with uniform square meshes. The calculation is applied to the rectangular grids usually used in high voltage substations. The calculation results obtained by the propsed model are compared to the results obtained by other models and to the results of the analysis performed on the similar cases.

grounding grid; grounding impedance; mutual impedance; non-equipotential

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