Design Constraints of Disconnector Switch for Analysing Very Fast Transient Over-Voltages Employing Recurrent Flash Model

Gas-insulated substations have emerged over the air-insulated substations due to their stable operation with rapid development in transmission systems. However, abnormalities during switching operations in Gas-Insulated Switchgear pose significant challenges to system insulation and reliability, especially while operating with extra high voltages. This study explores the mechanisms contributing to its generation, emphasising the modelling of the disconnector switch under the influence of trapped charges and its diverse operating conditions in a 550 kV GIS, using a recurrent flash approach. This paper presents the examination of these overvoltage characteristics under various scenarios, with cautious observation of key factors used in its modelling to assess the disconnector full-scale type testing and to assist decisions on the various operating conditions. The reliability of the model is validated through simulation results and supported by field data from multiple studies. These outcomes inspire methods for optimising insulation design and operating protocols, hence boosting the system.