Epoxy resin casting material is an important basic material of high voltage apparatus

which is widely used in the manufacture of insulating parts.Its damage characteristics are of great significance to product design and test verification

but there are few related researches.The damage characteristics of epoxy resin casting materials for high voltage apparatus are studied by using acoustic emission technology.The tests of graded load retaining

graded repeated load retaining and graded repeated load retaining are carried out respectively

and the acoustic emission signals of materials in the process of damage are recorded.The experimental analysis shows that in the load bearing state the damage of the material is a process of gradual development and evolution

which can be roughly divided into three stages:initial stage

development stage and instability stage.The initial load value of the development stage is about（50%-60%） of the final failure value.The initial load value of the development stage indicates that irreversible damage has occurred inside the material

and there is a trend of continuous expansion.This phenomenon should attract enough attention in production practice.