Study On Breakdown Characteristics Of Transformer Oiland Streamer Discharge In Transformer Oil By Numerical Method

In the daily operation of the transformer,the most important internal insulation medium is transformer oil,thus it can be seen that the transformer oil plays a vital role in ensuring the stable operation of the power system.Therefore,the insulation performance directly affects the stable operation of the power grid.The research of the discharge theory in transformer oil is mainly from the study of the motion law and the popularization and application of charged particles in electric field.Both the experimental research or theory to explore the process of oil discharge principle,analysis of different conditions or rules of liquid discharge electrode system,and ensure all kinds of electric power equipment can be stable and safe operation has very important research value and application significance.At present,in the process of studying the discharge phenomenon in transformer oil,a great deal of research work has been done.Based on the comparison of domestic and foreign references and a series of transformer oil discharge theory and test results at the same time,the basic physical process of law,established a physical model of the development process of transformer oil discharge,including electrode structure and simulation calculation area.In the development process of streamer discharge in transformer oil,the main factors influencing its development process has two aspects,one is the motion of the charged particle in the electric field,on the other hand is the effect of space charge on electric field.Through the comparison of practice and the reference of a large number of references,it is feasible to determine the continuity equation of charged particles,and the spatial Poisson equation.At the same time,after consulting many related literature,find out the calculated empirical formula obtained from the streamer discharge in transformer oil testing by domestic and foreign scholars of transformer oil simulation of streamer discharge transport and reaction coefficient.Then,considering the different conditions of the physical model,the charged particle continuity equation and the Poisson equation,the boundary conditions and parameters are determined.In the process of solving the continuity equation of charged particles,the convection term is much larger than the diffusion term.Through the study on space charge in transformer oil generation and disappearance mechanism,the charged particles in the continuity equation expressions were determined,and then clear the field ionization effect is mainly the development process of streamer discharge ionization mechanism.Numerical simulation of streamer discharge in transformer oil using COMSOL Multiphysics simulation software to establish the corresponding two-dimensional fluid model symmetry axis,simulation pulse discharge process of ball plate voltage in oil under the influence of electrode,voltage and gap distance on the streamer discharge in oil development process.Through the simulation of the process of oil in the streamer discharge under different conditions,on the streamer development situation and characteristics,and on the basis of the simulation results obtained by the streamer discharge process,analysis of some factors affecting the development of the characteristics of the process of streamer discharge were analyzed.Because the working environment of transformer oil is very complex,the insulation performance of transformer oil is affected by many external factors in the actual operation of transformer.In order to understand the influence of different factors,the insulation characteristics of transformer oil design test on the different temperature and distance conditions,changes of breakdown voltage of transformer oil,and the test results are based on the theory and Simulation of streamer discharge.