Seismic Performance Study On Ultra High Voltage Converter Transformer

China is an earthquake-prone country,with continental earthquakes accounting for one-third of the world's mainland-destroying earthquakes,the most in the world.In recent years,the speed of power grid construction has accelerated,it is inevitable that more and more substations(converter stations),especially ultra high voltage(UHV)stations,will be built in areas with high intensity of defense and weak site conditions,which are unfavorable for earthquake resistance.The UHV converter transformer is the most core and critical equipment in the converter station,once damaged,it will cause the whole substation or converter station to shut down,threatening the safe and stable operation of the power grid.At present,the seismic research for UHV transformers mainly focuses on seismic capacity assessment,and lack of relevant research on its seismic response,isolation technology and seismic vulnerability.In this paper,the 1:3 model of ±800k V UHV converter transformer was designed,then the shaking table test of earthquake simulation was carried out,combining with simulation methods,the seismic response laws,seismic dynamic amplification coefficient of converter transformer body,isolation technique and seismic susceptibility of UHV converter transformer were studied.The main innovative research and achievements were summarized as follows:1.Based on the investigation and test,the weak links and parts of UHV converter transformer equipment under earthquake were studied,and the failure mode of bushings were analyzed.The failure modes of ceramic bushings and composite bushings in converter transformer were proposed.2.The effect of ignoring the gravity similarity ratio in shaking table was investigated,and the feasibility and reasonableness of the 1:3 ignored gravity model test scheme was demonstrated.The natural vibration characteristics,seismic performance and seismic response laws of the UHV convert transformer structure were obtained.The results showed that the response of the bushings of converter transformer under the combination of horizontal and vertical seismic effect was generally greater than that of the equipment under the single horizontal seismic effect,and the evaluation of the seismic performance of this type of equipment should consider the combination of horizontal and vertical seismic.3.Through the shaking table test,the distribution law of stress seismic dynamic amplification coefficient and acceleration amplification coefficient of converter transformer body were studied,and the definition of seismic dynamic amplification coefficient of UHV converter transformer body was also studied.Combined with the test and simulation methods,this paper studied the seismic dynamic amplification effect of the converter transformer body on its bushings,analyzed the influence of the converter transformer body stiffness on the seismic dynamic amplification coefficient,and studied the technical measures to reduce the seismic dynamic amplification effect of the converter transformer body.The seismic dynamic amplification coefficient of UHV converter transformer body was proposed to be between 2.0 and 2.3.4.Through the finite element simulation analysis,the influence of the parameters of the isolation devices on the seismic response and isolation efficiency of the converter transformer was studied.Combined with the verification of the shaking table test,the selection of the parameters of the isolation devices and the isolation design principle for the UHV converter transformer were proposed,which provided the basis for the isolation design of the converter transformer in the high intensity seismic areas.5.Considering the uncertainty of seismic input,the probabilistic seismic demand model of UHV converter transformer structure was established.Through the seismic performance analysis of converter transformer under different seismic records,the bushing stress required for equipment vulnerability analysis were obtained.Based on the probabilistic seismic vulnerability analysis theory,the failure probability of converter transformer equipment under different seismic intensity was calculated,The seismic vulnerability curve and comprehensive vulnerability curve of each bushing of converter transformer were drawn,and the seismic performance of UHV converter transformer was evaluated from the perspective of probability failure.In this paper,the seismic response laws of UHV converter transformer were studied in detail,the seismic dynamic amplification effect of the converter transformer body on its bushings was analyzed,then the value of the seismic dynamic amplification coefficient of the UHV converter transformer body was proposed.Also the seismic isolation design principle of UHV converter transformer was proposed,the seismic vulnerability curve of the equipment was established,then evaluate the seismic performance of UHV converter transformer from the perspective of probability failure.The results of the study can improve the seismic design level of UHV converter transformer.