Seismic analyses for power transformers

Reliability and security of power systems, especially in areas prone to earthquakes, depends on the seismic withstand of its components and interaction of these components with other elements. All relevant power products and components should be designed and tested to guarantee high seismic performance. Option which is strongly recommended for seismic qualification is shake table test. This way is very expensive and in some cases like power transformers impossible due to its weight and size. Because of this the numerical analyses can be very helpful to determine the dynamic characteristic of the system. This way is more and more used during evaluation of seismic performance of power products, especially in the design phase. In the paper a different numerical approaches for seismic analyses of the power transformers have been presented. In the first part of the article focus was put on typical simulation methods defined by IEEE and IEC standards. This approach is dedicated only for transformer’s components. Due to fact that standards do not provide clear information about fluid influence on power equipment during seismic events, some investigations related with oil filled transformers were done and summarized. Three different numerical methods were investigated. First one is built based on the Fluid-Structure Interaction (FSI) methodology. In this approach combination of different software (CFD, structural, and coupling code) is used to cover phonemes related with fluid dynamics and structural analyses. FSI methodology gives a wide possibility but, it’s very complex however, is very complex which can be a disadvantage for very complex objects. Next one uses acoustic elements, where the fluid is modeled as acoustic medium. This is method which allows to take into account fluid during seismic simulations in simplified way. The last one uses Lagrange and Euler element formulations (CEL) in which sloshing effect of the oil in power products can be considered. All this approaches can be very helpful to determine the dynamic characteristic of the transformers and its equipment including fluid.