Research On Diagnosis Of Aging Condition Of Oil-paper Insulation Transformer

The power transformer is responsible for the conversion and transmission of power in the power system,which affects the reliability and safety of the power supply system.It is an indispensable power equipment in the power grid.Because the life of the transformer is mainly determined by the insulation performance of the transformer,the fault of the transformer is mainly caused by the insulation aging.It is necessary to avoid the fault of the power transformer to affect the normal operation of the power grid,and it is necessary to diagnose the insulation aging of the oil immersed transformer.At present,the diagnosis of oil immersed transformer is mostly based on the non destructive dielectric response method to establish the equivalent model of oil-paper insulation to diagnose the aging condition of transformer oil-paper insulation system.The return voltage measurement of time domain dielectric response method is used to study the relationship between the equivalent circuit parameters of the oil paper insulation and the insulation state of the transformer based on the equivalent Debye model of the oil paper insulation system,and then the characteristic parameters of the return voltage are used to diagnose the oil paper insulation of the transformer.The research ideas and main contents of this paper are as follows:Based on the diagnosis results of transformer oil-paper insulation aging at home and abroad,it is found that the polarization characteristics of transformer oil-paper insulation can be studied based on the theory of dielectric response.First,the aging mechanism of transformer oil-paper insulation was studied.The basic theory and polarization characteristics of the dielectric were introduced.Then the dielectric response detection method was introduced based on the mathematical theory of dielectric response;then the physical structure of oil-paper insulation was gradually established.The equivalent Debye model of the oil-paper insulation system uses the recovery voltage method to derive the Debye model's return voltage measurement formula.At the same time,the polarization spectrum and the initial slope curve of the return voltage can be obtained.According to the change of the parameters of the equivalent circuit in the insulation state of the transformer,the equivalent circuit of oil-paper insulation needs to be identified.In this paper,the initial slope of the characteristic voltage of the recovered voltage is used to establish the optimization objective function,which reduces the collection of large amounts of experimental data.The fruit fly optimization algorithm was used to identify the parameters of the oil-paper insulation equivalent circuit,and the feasibility and accuracy of the fruit fly optimization algorithm were verified by examples.In this paper,the Debye equivalent model of oil-paper insulation is built by MATLAB software.The effect of the change of equivalent circuit parameters and test parameters on the polarization spectrum and initial slope curve of the return voltage is observed.The relationship between the oil-paper insulation state and the equivalent circuit parameters is observed.Then,the relationship between the characteristic parameters of the recovery voltage and the insulation state of the oil-paper can be obtained.When the state of oil-paper insulation is damped and aged,the polarization parameters of the equivalent circuit change,affecting the polarization spectrum and the initial slope curve.Combining the change of the polarization spectrum and the initial slope,diagnosis of transformer oil-paper insulation aging.