Seismic response of potential transformers and mitigation using innovative multiple tuned mass dampers

Porcelain electrical equipment, such as potential transformers (PT), are important components of power supply system that have experienced damage during past earthquakes. The goal of this paper is to propose and investigate the effectiveness of an innovative multiple tuned mass damper (MTMD) mitigation strategy for PTs using analytical and computational finite element methods. The paper discusses the reference seismic performance of two non-controlled typical 110-kV and 220-kV PTs through shake table tests. A novel MTMD damping device is proposed for the 220-kV PT and the effect of different parameters such as the number of mass units and mass ratio is investigated first using analytical solutions for harmonic excitations. Next, a finite element model for the PT is developed and validated using the shake table tests. The model is used to investigate the MTMD damping effectiveness and robustness using linear and nonlinear time history analysis under seven different earthquake records. Large mass ratios, up to 30% of the PT weight, and different number of mass units, up to 9 units, are considered in optimizing the MTMD design parameters and studying its limitations with focus on detuning effect and geometric nonlinearity. A nonlinear time history analysis is also conducted for controlled and non-controlled to determine the effectiveness of the proposed MTMD in withstanding larger earthquakes. The analysis is extended to interconnected equipment and systems to study the conductors' influence on the MTMD effectiveness. The study concludes that PT controlled using MTMD demonstrate a superior seismic performance and can withstand earthquakes with about 30% larger intensity when compared to non-controlled cases. The proposed MTMD is practical and can have a great potential in mitigating substations seismic damage if extended to other electrical equipment.