Research On Condition Evaluation Technology Of Epoxy Resin Dry-type Insulation Equipment Based On Dielectric Spectrum And Activation Energy

The application of dry-type insulation equipment in the power grid is becoming more and more common,but the structure of dry-type insulation equipment is complex,the insulation defects are diversified,the aging degree in the process of use is deepened,and the safe and stable operation of the substation is seriously affected.At present,the research on dry-type insulation equipment is mostly focused on macroscopic aspects such as parial discharge,while the chaxacteristics of epoxy resin itself are relatively small.As a result,the aging process and mechanism of dry-type insulation equipment have not been studied in depth,and the insulation state cannot be achieved.And accurate and reliable assessment of remaining life.For this reason,it is necessary to develop more effective insulation detection methods to reliably evaluate the internal defects and insulation conditions formed during the pouring of dry insulation equipment.The material aging process is actually a chemical reaction process.The activation energyrepresents the energy barrier to be overcome by the chemical reaction.It can directly reflect the difficulty of cracking the insulating material.It is an intrinsic property of the aging process of the material.There are few studies that can evaluate the status of dry-type insulation equipment.In order to study the relationship between the activation energy of epoxy materials and the aging state,this article designs an aging cxperiment,and sets up an aging experiment platform and a dielectric temperature spectrum measurement platform.In the course of the experiment,it was found that the existing frequency-temperature translation method for calculating relaxation activation energy based on dielectric spectrum has problems of physical basis and unclear applicable conditions.By improving the Debye equation,we obtained ε" and ε’ with frequency.The translational physical quantities corresponding to different relaxation types are divided.The experimental results show that,due to the different degrees of influence of temperature on different relaxation processes,the total dielectric spectrum curve shifts to the upper right as the temperature rises,that is,the phenomenon of"temperature drift" In order to solve the "temperature drift" phenomenon,this paper proposes an improved dielectric spectroscopy method:the first derivative of the total dielectric spectrum curve G’(Inf)is used to eliminate the secondary relaxation process that does not change much with frequency f The effect of the curve approximates a single relaxation process,and epoxy resin is used as an example to verify the effectiveness of the improved dielectric spectroscopy method.In this paper,the dielectric spectrum and electrical strength of epoxy resin samples for dry-type insulation equipment under different aging degrees and different temperatures were measured,and the relaxation activation energy of each state was calculated.As the aging progresses,the relaxation activation energy of the epoxy resin decreases,increases,slightly decreases,and eventually rises.The dielectric loss factor and the relative dielectric constant show a tortuous rise,and the breakdown field strength shows a tortuous decrease.Borrowing the Arrhenius equation to obtain the thermal aging acceleration factor AF,the high temperature accelerated aging time can be converted into the operating temperature operating time.In this paper,the breakdown strength of the sample is reduced to 50%of the initial value as a sign of the end of the material life.The relaxation activation energy corresponding to the end of the life of the epoxy resin material is 209.741 kJ/mol.This paper establishes a method for judging the dry insulation state and predicting the life of epoxy resins based on activation energy.Taking the dry-type transformer as an example,the dielectric spectrum measurement wiring method and test method of dry-type insulation equipment are proposed,and the initial relaxation activation energy of the dry-type transformer scale model numbered A,B,and C are 71.229 and 74.267,respectively,79.412 kJ/mol,the relaxation activation energy increased significantly after 45 days of aging time in the aging cabinet at 100℃,130℃,and 160℃,and the remaining life of the three shrinkage models was predicted.The relaxation activation energy of dry-type transformer 1 and transformer 2 are 76.046,69.373kJ/mol,and the remaining life of transformer 2 is predicted,and the minimum remaining life is 36.486a.