Seismic safety evaluation of power transformer based on response spectrum method

Abstract

Power transformers are key components in power distribution systems and ensuring transformer do not be destroyed in the earthquake is critical to the safe operation of power transmission grid. Finite element analyses of power transformer under the earthquake, dead load and wind load are described in this article. The simulation results show that the structure could resist to seismic load and wind load according to GB 50260-2013. Introduction Power transformers are one of the most important equipment in substations, however sometimes they might be seriously damaged in strong earthquake especially the porcelain bushing often be occurred the root fracture failure. The present calculating methods for seismic resistant are: static method, spectrum response and step-by-step integration. The concept of the ‘response spectrum’ was applied in design requirements in the mid-20 century; it comes into widespread use as the primary theoretical tool in earthquake engineering in the 1970s when strong-motion accelerograph data became widely available. The Spectrum response is the dynamic analysis method in consideration of both structure dynamic performances and movements of the ground, the time consume of computation is being much saved due to its simple theory. Finite element analysis FE model creation The geometry model of power transformer should be simplified before the finite element model creation. Many elements, which are not structural ones and have non business with the vibration, have been omitted to simplify the analysis. However, their mass are still kept in the finite element model as non-structural mass. Before the nonlinear finite element analysis, it is necessary for the model to be discretized. The Figure.1 showed how the geometric model was meshed. To mesh the model, linear quadrilateral element S4R, linear line element of type B31 and linear hexahedral elements of type C3D8R have been used. Figure 1 Shell-beam combined FE model of the transformer 3rd International Conference on Machinery, Materials and Information Technology Applications (ICMMITA 2015) © 2015. The authors Published by Atlantis Press 1139 Boundary and load There are four load applied to the transformer, gravity, hydrostatic pressure, wind load and Seismic load. The gravity is related to the density of the material which is record in the Table 1. Table.1 Material parameter Material properties Young’s Modulus(Gpa) Posson’s ratio Density (Kg/m3) Q345 steel 210 0.3 7850 The hydrostatic pressure is caused by the oil stored in the transformer. As the inner wall of container was pressed on account of the oil density and the distance to the free surface, the press can be calculated by equation 1: