Combined Horizontal-Vertical Seismic Isolation System For High-Voltage Power Transformers

Published February 25, 2019

Graduate Students: Donghun Lee

Principal Investigator: Michael C. Constantinou

Project Completion Date: 10-31-2017

A three dimensional seismic isolation system was developed and experimentally validated for high-voltage electric power transformers of weight in the range of 300 to 800kip.  Although the validation concentrated on electrical transformers, the system is currently (2019) under construction in a hospital in California.


high-voltage power transformers.

It is generally recognized that seismic isolation systems for all applications, including electrical transformers and other equipment, provide for a substantial reduction in response  only in the horizontal direction.  Vertical ground motions are transmitted through the isolation system unchanged or even magnified.   The project concentrated on the development and validation of a practical three-directional seismic isolation system for use in high-voltage power transformers, although the technology could be easily transferred to building applications. Characteristics of the developed system are: (a) it is a modular extension of a horizontal seismic isolation system currently used for power transformers, (b) it consist of two separate systems, one to achieve horizontal seismic isolation and the other to achieve vertical seismic isolation, (c) the horizontal system is highly flexible in order to achieve a high degree of seismic isolation but subject to constraints on displacements for serviceability of the equipment, (d) the vertical system is able to support the weight of the equipment with limited deflection in order to meet serviceability requirements and compactness, (e) all components of the system are readily available from reputable manufacturers, and (f) all components of the system are passive and highly reliable.  The developed and tested system consisted of triple Friction Pendulum bearings for the horizontal isolation system, which are supported by vertically driven spring-damper units.  These units form a highly damped vertical damping system.



This project is supported by the Bonneville Power Administration, Portland, OR.