A separated three-dimensional isolation system for mitigating seismic response of ultra-high voltage converter transformer: Shaking table test and numerical simulation

With the large-scale construction of transmission line systems, converter stations are increasingly being built in high-seismic-intensity areas. As a critical component, ultra-high-voltage (UHV) converter transformers, if damaged, can cause power outages, making their seismic performance crucial. This study proposes a novel separated three-dimensional isolation (STDI) system to reduce the seismic response of UHV converter transformers, and the system's configuration and design parameters are introduced. A scaled model of the transformer and its isolation system is developed based on an actual project, and a series of shaking table tests are conducted to evaluate its performance. Moreover, a refined finite element model is established to investigate the isolation efficiency under seismic excitations with different spectral characteristics, and the experimental results confirm the model's accuracy and demonstrate the system's effectiveness under both near- and far-field seismic waves. Results show that the STDI system reduces transformer bushing acceleration and strain by over 70 % horizontally and 61 % vertically. As the peak ground acceleration (PGA) increased from 0.3 g to 1.2 g, the STDI system's isolation efficiency varied by only 10 %, indicating low sensitivity to amplitude. Under near-field seismic waves, the horizontal isolation effects range from 61 % to 82 %, and the vertical from 42 % to 65 %. For far-field seismic waves, horizontal and vertical isolation remain above 62 % and 44 %, respectively, indicating the STDI system can address seismic excitations with different spectral characteristics.