Seismic Vulnerability Analysis of the ±800kV Converter Transformer Before and after Coupling

The transformer-bushing system, a critical component in substations, sustains significant damage during earthquakes. To investigate the response characteristics and seismic vulnerability of transformers during earthquakes, a detailed finite element model of a ±800kV converter transformer was developed. Additionally, a simulation model of the converter transformer coupling system was created based on the actual coupling method. The seismic response time histories of both individual equipment and the coupling system were calculated, and the response characteristics and seismic vulnerability of the equipment were assessed before and after coupling. The results indicate that the first four modes of both the single device and the coupled system are concentrated in the valve-side bushing and the network-side bushing, which are identified as vulnerable points in terms of earthquake resistance. The peak stress response of the coupled system exceeds that of the single device, leading to a higher likelihood of bushing failure under seismic conditions. The coupling negatively impacts the seismic performance of the converter transformer. Various connection methods such as decoupling should be considered to reduce the adverse effects of coupling.