Grounding Performance under Lightning Surges in High Voltage Substations
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- Geophysical Institute 
To achieve electromagnetic compatibility (EMC) and sufficient protection against lighting transients in the power transmission system, understanding of the grounding system transient behavior becomes crucial when deviating from international design standards and recommendations. To consider design deviations the present work is focused towards developing a method of integrating simplified grounding system models in transmission systems and perform lightning transient analysis on both parts to evaluate a particular design case. Firstly, the grounding system models for substation grounding grids, with a variety of configurations and sizes, is implemented. The characteristic transient response of the grounding system is visualized through simulations to study the sensitivity of configurations and modified soil parameters during current injections. The method of implementation allows for a detailed view and pre-processing of large data-sets from simulations. The advantages of this method is used to extract overall measured values to create a tool for EMC analysis and in addition processing different parameters and functions of the grounding system. Secondly, the grounding system model is integrated into transmission systems using a newly released interfacing application. The application allows for co-simulation between the development software of the grounding system and a specialized tool for the transmission system. The innovation of this modeling approach is given as a contribution to an international conference by submitting a paper. Finally, the integrated grounding models and transmission system are studied with two substation design cases; a short and long cable between surge arrester and transformer. The short cable case follows well-known design standards where the long cable case is a design deviation which is common in larger domestic hydropower plants. Even though the long cable case is deviating from design recommendations, the results show a less negative impact on the grounding system compared to the short cable case.