Power Transformer Oil-paper Insulation Aging Condition Diagnosis Method Research

Power transformer is the key equipment of power transmission and distribution,The aging failure of oil paper insulation system are main causes of power transformer accident,timely and effective diagnosis of its aging condition is the basis and the key technique to ensure the safe operation of power grid and prolong transformer operating life.The subject derives from the National Natural Science Foundation Project of China that is the diagnosis method of transformer oil-paper insulation based on circuit analysis and recovery voltage response(item number:61174117).This paper takes oil-paper insulation transformer as the research object,and further researches the relationship between the return voltage curve and the characteristic parameters of the voltage and the insulation state of the transformer,Build the extended Debye model and equivalent circuit and design simulation platform.Through many simulations and experiments,the recovery voltage characteristics of oil paper insulation system are discussed.further tap the relationship between new characteristic information and Insulation Aging.The diagnosis model of return voltage is established,which is based on the combination of the equivalent circuit parameters and the characteristic parameters of the recovery voltage.The return voltage diagnosis mentalities combine with the field test results,and it is feasible that using the recovery voltage characteristic parameters to diagnose insulation condition,Which providing a new approach to the diagnosis of oil paper insulation condition.The main works of this thesis are listed as following:1.Based on the extend Debye dielectric response model,the analytical expression of the equivalent circuit of return voltage,On the basis of understanding differential time domain function theory,the solution of the response voltage curve is obtained According to the actual condition of the insulation system,the number of the polarization branch of the equivalent circuit can be determined.which solving the problem of the unknown number of insulation equivalent topology.and adopting Interval-Particle Swarm to identify equivalent circuit parameters of dielectric response.2.Theoretical derivation and simulation experiments to verify the test parameters optimizing of dielectric response.Under different polarization voltage,charge and discharge time ratio,Separately analyzing the characteristics of voltage curve and polarized growth curve and the changing of return voltage characteristic parameters.Therefore,the optimal value of polarization voltage and charge to discharge time ratio are determined.3.According to the structural characteristics of the actual transformer,Designing the oil paper insulation "double" type analog insulation system,The effects of air gap(bubble),water,paper aging and the characteristics of the response voltage are studied.In particular,the effect of the return voltage method on the air gap in the insulation system is studied,The research has a good extensive practical application prospect.4.The characteristic information of the return voltage curve is excavated to investigate the new characteristic parameters of the return voltage of dielectric relaxation response.Relative stable return voltage and half life characteristics are study by Simulation analysis.Taking the reliability of the actual operation into account,return voltage half-life is determined as the new parameter of dielectric relaxation response.Finally,Basing on peak time,the initial slope,half life of return voltage and equivalent circuit,which can provide a new comprehensive method for diagnosic oil-paper insulation condition.