Research On Wave Process And Insulation Performance Of 500kV Power Transformer

The most important condition for safe and stable operation of power transformers in power system is that the power transformers have stable and reliable insulation capacity.In recent years,with the increasing voltage level of the transmission line,the enhancement of regional interconnection and the increase of the capacity of single machine installed,it will inevitably level also puts forward higher requirements for transformer insulation.The insulation of the transformer has been increasingly serious problem.It has been proved that the mainly transformer fault is the insulation issues.Therefore,this paper studies the windings wave process,and the main and longitudinal insulation performance of the transformer has been researched.It is significant for insulation design of the power transformers.Firstly,based on the distributed parameter circuit model,a model was built for the internal winding structure of a 500 kV power transformer.The mathematical value of the vertical equivalent capacitance,inductance and resistance was determined by mathematical calculations.At the same time,the values of ground capacitance,ground inductance,and resistive parameters of the vertical insulation simulation model for power transformers are established.Then,Simulink simulation software is used to simulate the wave process of the winding in different working conditions of 500 kV power transformer.The initial potential,steady-state potential and oscillating potential distribution were simulated respectively for the neutral point grounding and the neutral point insulation.The weak link of the winding and the gradient voltage distribution are obtained,and the influence of the winding neutral point grounding or the neutral point insulation on the high-voltage winding wave process is analyzed and compared.All of the results will provide a theoretical basis for the design of longitudinal insulation.According to the existing theory,the insulation problems of power transformers are mainly embodied in two aspects,that is,the main insulation and the longitudinal insulation of the power transformers.Based on the existing theories,the main insulation parts of power transformers are studied and simulated.According to the main insulation structure of the 500 kV power transformer,a simulation model was established.The electric field of the power transformer is calculated by the finite element analysis software,and the potential distribution and the field strength distribution are given.The insulation margin of the end electric field is calculated,which provides a basis for the design of the main insulation structure of the power transformer.Finally,based on the calculation results of the wave process,a simulation model of the longitudinal insulation electric field between the transformers is established near the position of the maximum gradient potential distribution between the transformers.The gradient voltage boundary is applied to the corresponding coils,and the finite element software is used for simulation analysis.The distribution of electric field strength at a typical location is given and a reference for engineering design is provided.