Characteristic Study On Transient Electric Field And Insulation Of Converter Transformer

High voltage direct current(HVDC)transmission technology has great advantages for the transmission network with far distance or large capacity capacity and the interconnection of power systems.Therefore,all countries in the world will carry out research and application of DC transmission and transformation technology.China began in-depth research and Exploration on HVDC transmission in 1980.Moreover,in 1990,domestic scientific research institutions and power experts have made breakthroughs in the research and development of HVDC transmission and transformation technology in China.After twenty years of development,the domestic HVDC transmission system has developed from ±500kV to the world's highest level transmission system of ±800kV HVDC transmission system consists of rectifier station,DC line and inverter station,and the key equipment of AC/DC converter is converter transformer.The distribution law of transient electric field between different windings is studied by using different insulating oil or insulating paper in the converter transformer,that is,to master the distribution law of the electric field in the change of the long time DC voltage and the polarity reversal voltage.In this paper,frequency domain spectroscopy(FDS)is used.Two main parameters(relative dielectric constant and electrical conductivity)of insulation properties of plant oil,mineral oil and insulating paper materials are measured under different conditions(frequency and temperature)by the broadband dielectric resistance spectrometer.In this paper,the analog ±500kV change end is designed on the basis of the parameters of the converter pressure converter provided by a domestic transformer manufacturer.The simulation model of ±500kV converter winding is designed.In this paper,the insulation material is experimentally tested,and the corresponding insulation characteristic data are obtained.On the basis of this,the main insulation of the converter is analyzed by finite element method.In order to get the change law of the electric field of the actual converter transformer at the moment of polarity reversal,the change of the electric field distribution is studied in this paper mainly on the change of the reversal time and the electrical characteristics of the material.The results show that the characteristics of sample insulation are related to temperature and frequency,and the distribution of transient polarity reversal electric field is related to the characteristics of insulation materials.The above experiment and research provide reference for insulation design and improvement of domestic converter transformer.