Ефикасен електромагнетен модел за анализа на преодни појави кај големи заземјувачки системи во слоевита земја

Abstract

The electromagnetic model, which is based on the method of moments solution of the mixed potentials electric field integral equation, is one of the most accurate and popular models for transient analysis of grounding systems, especially in the case of atmospheric discharges. Its practical application has been hampered by the large amount of computer time required for numerical integration of the Sommerfeld integrals, which are at the core of this exact model. These integrals are singular, oscillatory and slowly converge, therefore, analysis of large grounding systems are usually performed using approximate methods based on the image theory. The need for an accurate model, for the calculation of transients related to atmospheric discharges, has been increased by the increasing need for protection of electronic equipment that is at the core of modern critical installations, and such installations are fundamental for the modern society. This dissertation presents several approaches for improving the efficiency of the electromagnetic model and extending its application domain for precise analysis of high frequency and transient phenomena in large grounding systems, with complex electrode configurations, in a homogeneous or multilayer earth. The accuracy of the model is verified by comparison with published numerical and experimental results. For the first time, a parametric analysis of induced transient voltages in a large grounding system in layered earth, due to atmospheric discharges, has been performed by this model. The analysis also showed cases where approximate methods cannot be applied due to high imprecision.