Development Of High Thermal Conductivity Epoxy Potting Adhesive For Dry-type Transformer

With the continuous development of China's economy,people's demand for power consumption in work and life is increasing,so the load of transformer is also increasing.Potting type dry-type transformer plays an important role in the operation of power grid.In the working process of transformer,part of electric energy is converted into heat energy.If the transformer can not dissipate heat in time,it is easy to cause circuit failure or transformer fire.At present,the thermal conductivity of castable for dry-type transformer is between 0.4-0.5 w /(m · K),which leads to the low heat dissipation efficiency of the whole transformer.Therefore,improving the thermal conductivity of potting adhesive for dry-type transformer is a practical research goal.In this study,the main purpose is to improve the thermal conductivity of epoxy potting adhesive,taking into account its electrical properties,mechanical properties,processing technology,economy and so on,in order to prepare an epoxy potting adhesive for some transformer plants.This project can be divided into three parts: the compounding and modification of filler powder,the preparation and curing of potting adhesive,and the improvement of other properties of potting adhesive.First of all,silica is selected as the filling powder of the potting adhesive,and silica powder is compounded to improve the filling amount of silica powder in the epoxy resin,and a high free range phonon propagation channel is constructed to improve the thermal conductivity of the material.The coupling agent suitable for silica and epoxy system was selected from different kinds of modifiers by referring to relevant literature.The coupling agent used for powder modification was determined to be CG-7 by experiment,and the appropriate dosage range was 1.5 ~ 2%.The drying condition of powder was determined to be 150 ? / 6h,and the moisture content(DSC)was 0.11%.According to the existing modification equipment,the optimal reaction conditions between the powder and the coupling agent and the storage period of the modified powder were explored.The results showed that the longer the storage time or the higher the reaction temperature,the higher the activation degree of the modified powder,and the worse the technical performance of the prepared potting adhesive.Therefore,the modification reaction conditions were 30 ? / 2h,and the grafting rate was about 9%.Then the above active powder was filled into the epoxy anhydride system,and the amount of epoxy resin and anhydride curing agent was determined to be 100:85 through experiments.The active powder was filled into the potting adhesive system according to the mass,and the suitable filling amount was 72-75%,and the thermal conductivity was 1.0-1.8 W /(m · K)then according to the exothermic curve of curing reaction detected by DSC,three characteristic temperature points of curing reaction,starting temperature,peak temperature and ending temperature,were calculated.The best curing process was verified by experiments as 80 ? vacuum / 0.5h,80 ? / 4h,90 ? / 3H,110 ? / 2h,140 ? / 5hFinally,according to the market demand,the flame-retardant powder was prepared by adding appropriate amount of aluminum hydroxide to improve the flame retardancy of potting adhesive.In view of the settlement of potting glue in the process of casting and transportation,the storage problem of potting glue was improved by adding superfine heavy calcium with less thickening.