Effect of Pressboard Ageing on Power Transformer Mechanical Vibration Characteristics

Power transformer winding clamping pressure is a critical parameter, which is directly related to transformer short circuit ride through capability. Mechanical impacts generated on the winding structure during short circuit faults, switching surges and other high current faults have a significant impact on the winding clamping structure and could lead to reduce the clamping pressure. The change in clamping pressure influences the vibration behaviour of winding structure. Hence, variations in clamping pressure can be assessed by monitoring the transformer vibrations. However, it has been observed that, not only progressive loss of clamping pressure but also solid insulation ageing has a significant influence on the winding vibration characteristics. Therefore, for a proper analysis of transformer vibration a clear understanding of the effect of solid insulation ageing on vibration behaviour of transformer winding structure is essential. This study aims to investigate the sensitivity of the transformer winding vibration characteristics to ageing of solid insulation material. Variations in modal parameters of winding structure with solid insulation ageing is studied using Finite Element Modelling (FEM). Results are used to discuss the sensitivity of winding vibrations to solid insulation ageing.