Analysis of Trapped Charge Effects on Very Fast Transient Overvoltages in 400 kV Gas Insulated Substations: Modelling, Simulation, and Implications for Design and Operation

This paper investigates the impact of trapped charges on Very Fast Transient Overvoltages (VFTOs) in 400 kV Gas Insulated Substations (GIS) systems. VFTOs pose significant challenges to the design, insulation coordination, and long-term reliability of GIS systems. To study the effects of trapped charges on VFTO magnitudes, the paper utilizes the Alternative Transient Program - Electromagnetic Transients Program (ATP-EMTP) and MATLAB for modelling and simulation. The analysis is performed at various locations within the GIS system and under different trapped charge conditions. The results reveal that trapped charge significantly influences VFTO magnitudes, with the highest values observed in the middle of the busbar and the lowest at the disconnector switch. The paper emphasizes the importance of considering trapped charges when modelling high voltage systems to obtain a more accurate representation of electrical behavior. Furthermore, the study highlights the need for focused analyses on specific conditions and locations within the GIS system to ensure reliable results. The findings presented in this paper contribute to a better understanding of VFTO behavior in GIS systems, which can help improve insulation coordination, GIS design, and overall system performance and reliability.