Research On Aging Condition Assessment Of Oil-paper Insulation Transformer Based On The Time-domain Dielectric Response

In recent years, power transformer as a part of grid is playing an important role in the power transmission and distribution.Insulation deterioration is a major "killer" in transformer’s career,so it is significant and necessity to test and assessment the situation of transformer oil-paper insulation system in time.In recent time,the method based on the dielectric theory in diagnosing oil-paper insulation is the most popular and newest method.This paper take oil-immersed transformer oil-paper insulation system as an object.Using dielectric theory to built equivalent Debye model.Analyzing the relationship between the time domain dielectric response characteristic amount and the oil-paper insulation degradation,it proposes new ideas and methods for aging the oil-paper insulation system. The main ideas and content of the paper is as follows:It first introduces the concept of dielectric in some detail starting from the time domain dielectric theory.Then introduce the theories and types of dielectric polarization.Deriving the mathematical theory of dielectric derivation. Establishing the equivalent Debye model of oil-paper insulation system,introducing the theory and testing procedure of Return Voltage Method.Deriving the reply voltage formula of the complex method containing numbers of polarization circuit.Using Particle Swarm Optimization to identify the parameters of Debye model,and it gives the detailed steps based on the time-domain dielectric response and Debye model.In the case of transformer T1 and T2,the parameter of Debye model with six polarized circuits was identified.Comparing the polarization spectrum curves of calculating with the testing curves to verify the feasibility of this method.Researching the influences of the charging voltage and the ratio of charging and discharging time to the return voltage curve by simulation.Comparing the polarization cure from Debye model with different polarized circuits with the testing polarization cure. Simulation analysis the influence of the change of parameters in Debye model to the polarization cure,and find out the relationship between the change of parameters and the condition of Oil-paper insulation. It is shown that the charging voltage is directly proportional to the maximum value of the curve,to the ratio of charging and discharging time,the relation of the maximum value approximately showsthe exponential function relation. Proposing the idea that using the Debye model with six polarized circuits to diagnosis the insulation condition of the transformers with certain running time.With the decline of the insulation condition of Oil-paper insulation system,the geometric resistance increases and geometric capacitance stays the same,the polarization resistance decreases,the polarization capacitance increases. It is shown that the relationship between the change ratio of geometric resistance and the maximum value of the curve are related in quadratic function It analyses the relationship between the polarization curve and the materials of insulation system,it proposes an improved method that diagnosing the insulation condition with the front,middle and rear sections of the polarization curve and the characteristic polarization spectrum.