A number of application examples in power systems engineering demonstrate state-of-the-art modelling in electrical engineering and energy informatics. Power system models and advanced simulation and analysis methods are required within the process of the energy system transformation towards CO2-neutrality. Growing demand for energy from environmentally friendly sources is challenging modern grids to provide a reliable power supply that includes high fluctuating sources. Power grid operators must ensure that energy networks continue to provide the highest levels of reliability and performance at reasonable cost. Grid modelling and analysis supports the design and engineering of the power grids transition process with various states of grid evolution from its present centralized, carbon-based architecture to a future de-carbonized state. The present contribution discusses various power grid modelling applications within the context of the energy transition process in Germany. Two modelling areas, Schleswig–Holstein and Baden-Württemberg, respectively, demonstrate the challenge of load/generation balancing of a region with very high wind-power generation with another region characterized by high electricity demand due to its industry and population density structure. In doing so, electric power system modelling and simulation is shown as a technological ‘art form,’ highlighting that the experience of the engineer is of paramount importance when it comes to defining the system under consideration.