Study On Anti-Earthquake Ability Of Power Transformers

A lot of parts of China are located on areas where seismic activities are higher, the direct economic losses caused earthquake are number hundreds of millions, while indirect losses are uncountable. One of the main reasons which increase in indirect losses is damage of equipments in power system which retard the rescue works.Transformers are the critical equipments in electric power system. If transformers damaged in earthquakes, the power supply will be cut, such will produce a direct impact over other working post- earthquake. The performances of transformer with seismic resistance are discussed in this paper.The present calculating methods for seismic resistant are: static method, spectrum response and step-by-step integration. The results in static method are more different with actual situation; this method is dispensed with gradually. Spectrum response is dynamic analysis method in consideration of both structure dynamic performances and movements of the ground, the time consume of computation can be much saved due to its simple theory. Immediate dynamic analysis (also called step-by-step integration) is used for calculating the seismic response of the structure by designing the ground acceleration. This method is conformed to actual situation, but a lot of calculations should be needed. The above calculating methods are widely used in other fields such as architectural engineering, but deficient in electrical equipment seismic resistant performances calculation. The above calculating methods are adapted to transformer seismic resistant calculation. This paper analyzed both spectrum response and step-by step integration being used in transformer seismic resistant performances, and established the transformer seismic resistance simulated calculating method which deduces from calculations.For more practice to researching works, a real transformer (10kV, 630kVA) was tested on vibrating platform for seismic analysis. This type test is the first one in China. The change of transformer structure, deform of tank wall, stress on bushing are understood. Some important tested data are obtained. The tested data are summarized and analyzed, such lays a foundation for proving rightness and improving simulated calculating program.Through real transformer seismic test, the important data can be obtained. Through apply simulated calculating program, the weak points on transformer seismic activity are founded.Based on above research, the transformer design specification and calculate criteria for seismic resistant are given. When earthquake take place, main damages on transformer is as follow: bushing root are broken, welding between transformer mounting pad and rail are broken or mounting pad derailed, accessories of transformer or earthed bolt shorn. Therefore on the stage of transformer design and mount site, the bushing seismic resistant performance and transformer mounting schemes should be taken more consideration.The reliability of porcelain bushing, enforcement of transformer seismic resistance and some technical measures are sufficiently analyzed in this paper.The transformer seismic resistant design criteria (proposal) are also worked out in this paper.