Study On Fluid Structure Coupling And Vibration Characteristics Of Large Power Transformer

Power transformers are an important electrical equipment,the electromagnetic induction has been discovered from Faraday to the widespread use of large-capacity power equipment today,scientists from various countries have never stopped studying the transformer’s own vibration characteristics.The problem of transformer vibration and vibration noise comes from the structural vibration of the transformer when it is running.In severe cases,it will cause structural damage to its own important structures such as winding,iron cores,and shells.It also brings hidden dangers to the safety of the people living around the power plant.Therefore,studying the vibration characteristics of transformers and measures to reduce vibration and noise have become urgent problems for transformer manufacturers.This paper mainly studies the vibration characteristics of large oil-immersed three-phase power transformers during load operation,the research object is a 220 kV three-phase three-winding large oil-immersed power transformer,the research work can be divided into the following three points:(1)The 1:1 model of transformer simulation is established,the location of vibration source is found,and the vibration propagation path chart is also established.The vibration mathematical model of the core and winding of the vibration source is established.The modal analysis and calculation of the core of one of the vibration sources of the transformer are carried out under the constraint state.The calculation results are compared with the numerical calculation values.The simulation models of three kinds of preload tightening force are established,and the modal analysis is carried out.The modal data of vibration frequency and displacement under different preload tightening force are obtained.(2)The three-dimensional electromagnetic field calculation model of the core winding under the load condition is established.The magnetic density distribution and size of the core winding under the rated voltage load condition of the primary side are analyzed and calculated.The induced current and voltage value of single-phase high,medium and low-voltage winding in a single cycle are obtained.The maximum electromagnetic force of the winding is obtained through calculation,which provides the exciting force value for the subsequent simulation.(3)The solid-liquid coupling model of the transformer shell,oil and core winding is established,and the dynamic analysis of the fluid solid system under the load state of the transformer is carried out.The natural frequencies of the wet and dry transformer casings are calculated by the software.It is concluded that the natural frequencies of the transformer casings are higher than those of the wet ones in the dry state,and the causes of this phenomenon are discussed.Based on the solid-liquid coupling method,the vibration displacement state of transformer under different preload is analyzed,and the simulation authenticity of range gas field enhancement is established.Through the analysis,the vibration of transformer will be significantly enhanced when the winding is loose.Combined with the modal simulation data and the structural characteristics of the transformer,we can know that for large power transformer,we should pay more attention to the harm of low-frequency vibration.