Combined horizontal–vertical seismic isolation system for high-voltage–power transformers: development, testing and validation

The electric power network is considered to be critical infrastructure. Electric utility companies and electric power administrators are increasingly interested in strengthening the security and resilience of their networks against earthquakes. Important components of these networks are high-voltage electrical transformers. Earlier studies in the use of seismic isolation systems for electrical transformers and other equipment produced results that clearly show the benefits of seismic isolation in the horizontal direction. However, vertical ground motions were transmitted through the isolation system unchanged or even magnified. In response to this problem, this paper presents the development and validation of a compact, effective, reliable and cost-effective combined horizontal–vertical seismic isolation system for use in electrical equipment.