Research On Seismic Response Analysis And Isolation Design Of 500kV Capacitive Voltage Transformer

As an important component of lifeline engineering,the working status of the power system is related to whether social production and life can proceed normally.And because our country is located in an earthquake prone area,all previous earthquake disaster have caused huge losses to the lives and properties of our people,including great damage to the entire power system.In the power system,ceramic pillar equipment,due to its electrical functional requirements,is generally characterized by a slender structure,high center of gravity,high flexibility,low strength of post insulator materials,poor bending performance,and susceptibility to quasi resonance.It has been severely damaged in past earthquake disasters.Therefore,this article takes the 500kV capacitive voltage transformer produced by a certain factory in Xi’an as the research object.Through simulation earthquake shaking table tests,finite element analysis,isolation design,and vulnerability analysis,the seismic performance law and seismic performance improvement effect of the equipment structure are studied.The main work is as follows:(1)Determine the natural frequency and damping ratio of the equipment through simulated seismic shaking table tests,and obtain the acceleration and strain responses of key parts of the equipment.The test results show that the Fundamental frequency of the prototype structure of 500kV capacitive Voltage transformer in the X direction is 2.0Hz,and the damping ratio is 1.19%.The Fundamental frequency in Z direction is 44.7Hz,and the damping ratio is 0.10%.Under the action of synthetic Seismic wave with peak acceleration of 0.4g,the acceleration response peak,displacement response peak and stress response peak of Voltage transformer prototype structure are all within the allowable range,and there is no obvious structural damage and deformation at the test site.Under the action of synthetic Seismic wave with peak acceleration of 0.6g,the maximum acceleration response values of X and Z directions on the top of the Voltage transformer prototype structure are 4.50g and 2.12g respectively,the maximum relative displacement of X and Z directions on the top reaches 180.55mm and 135.77mm respectively,and the peak stress at the bottom of the lower casing reaches 47.5MPa,with a Factor of safety of 0.84,which is far lower than the Factor of safety of 1.67 specified in relevant specifications.The 500kV capacitive Voltage transformer equipment based on wire rope damper isolation support is tested on a simulated earthquake shaking table.The test data shows that under the artificial Seismic wave with a peak acceleration of 0.6g,the maximum acceleration response values in X and Z directions at the top of the Voltage transformer isolation structure are 1.24g and 1.00g respectively,the maximum relative displacement in X and Z directions at the top reaches 190.77mm and 148.35mm respectively,and the peak stress at the bottom of the lower sleeve is only 9.65MPa.This proves that the steel wire rope damper isolation support has an ideal effect on improving the seismic performance of equipment.(2)A simplified model of the prototype structure of 500kV capacitive Voltage transformer was established by using the finite element software Ansys and modal analysis was carried out.The natural frequencies of the finite element model in X and Z directions were 1.98Hz and 43.52Hz respectively,and the errors between the model and the test values were only 1.0%and 2.6%.Then the dynamic time history analysis under the action of artificial wave,EI Centro wave and Taft wave with the horizontal peak acceleration of 0.2g,0.4g and 0.6g respectively is carried out to calculate the error between the test value and the simulation value of the acceleration,displacement and stress response.The two are in good agreement,which proves that the establishment and analysis of the finite element model is reasonable and effective.(3)Using the Bouc Wen hysteresis model to approximate the energy dissipation characteristics of steel wire damper isolation bearings,and conducting seismic response analysis and comparison through numerical simulation.Placing isolation bearings at the bottom can reduce the acceleration and stress response of key parts of the equipment,but it will amplify the top displacement,and the isolation effect of the middle layer bearings is better than that of the bottom bearings.Under the same conditions,priority should be given to arranging isolation bearings in the middle layer.(4)The dynamic response analysis of the prototype structure of 500kV capacitive Voltage transformer is carried out under the coupling effect of ground motion and wind load.Under the coupling effect of ground motion and wind load with a peak acceleration of 0.6g,the Factor of safety of the prototype structure of Voltage transformer is 1.52,less than the Factor of safety 1.67 specified in the specification,and its safety reserve is obviously insufficient.After the bottom support and middle support are set,the Factor of safety of the Voltage transformer isolation structure is increased to 3.48 and 5.30 respectively,and its multi disaster resistance ability is greatly improved.(5)After determining the seismic weak position and critical response of the equipment,using the critical response level as the failure criterion,21 natural ground motions were selected for seismic vulnerability analysis of the equipment to verify the impact of strength failure and tensile failure on the equipment.At the same time,the failure probability of severe and ultimate tensile failure of equipment under different wind speeds was studied,which provides a certain reference for the multi disaster safety performance evaluation of other ceramic column equipment.