Seismic Standards Qualification of Instrument Transformers by Shake Table Test and Linear FEM Analysis

Abstract

Power grids are widely recognized as vital components of modern infrastructure. In today's society, nearly every aspect of daily life comes to a halt without electricity. Therefore, it is crucial to design power grids and their components to withstand various natural disasters. In this context, special attention is given to earthquakes and the need to enhance equipment resilience against this highly unpredictable event, which significantly impacts power grids.
 Instrument transformers could be the critical component in substations due to their slender design. Having this in mind, it is necessary to carry out further research and encourage development in order to reduce the impact of earthquakes on substations. Seismic qualifications are one of the means to achieve that goal.
 The primary objective of this paper is to share insights and experiences related to the preparation, implementation, and supervision of seismic tests conducted on a shake table. The FEM analysis, conducted as a crucial step in transformer design preparation and shake table testing, strictly adhered to the standards set by IEEE 693. IEEE 693 is widely recognized as the most demanding seismic standard regarding the substation equipment. Furthermore, the latest version of IEEE 693 was compared to other relevant standards, including IEC 61869 (current draft 38/652/CD), ETGI 1.020, and IEC 62271-300, to gain a comprehensive perspective.
 FEM analysis is characterized not only as a tool for design preparation and pre-test analysis but also as a valid tool for performing seismic qualifications, based on the comparison with the actual shake table tests. The paper extensively utilized the findings from seismic tests conducted on two distinct transformers, each employing different materials for critical components, in various test laboratories. These findings formed the basis for detailed analysis and conclusive insights, aligning with different versions of IEEE 693.
 This article aims to offer a comprehensive understanding of the seismic qualification process, providing valuable insights for substation designers, seismic specialists, and end users.