Introduction of an innovative base isolation system for seismic protection of HV components based on a combination of wire ropes and viscous dampers

Abstract

Upstanding electrical high voltage (HV) equipment, such as the 3AP3 circuit breaker and similar, are structural systems where operators and manufacturers are still requesting a simpler, more robust and cost-effective base isolation solution in order to manage the qualification for high seismic requirements. This paper provides a summary of the methodology used to develop a reusable, optimized base isolated system in terms of structure based stress reduction and cost efficiency, which will attempt to achieve qualification safely. The methodology used in this study combines numerical analysis and shakes table testing in order to achieve a cost efficient solution. First, the analytical models for the structure and the base isolation system consisting of wire ropes and viscous dampers are created on a commercial FEM code. Once the models are calibrated, the system is optimized to achieve an optimum performance at minimum cost requirements. Finally, qualification through a shake table test takes place based on the given most suitable configuration. The ITT Enidine wire rope isolator was the most suitable solution for this type of structure and multiaxis earthquake excitation. In order to effectively control rocking mode amplitudes, supplementary viscous damping was added. The adjustability of the system makes it reusable for other single supporter HV components with different physical weights and geometry or lower seismic requirements.