In the study, the GIS installation is modeled with surge impedance sections, with a lengthaccuracy of typically 0.5 m. The different characteristics of different GIS building blocks aretaken into account. Furthermore, the bushings are modeled with high accuracy, taking intoaccount their dimensions and capacitive grading if applicable. The 550 kV power transformersare either modeled with the specific surge capacitances (primary winding to ground, primarywinding to secondary winding and secondary winding to ground) or with a specific high-frequency transformer model which has to be provided by the customer.