Effects Of Temperature And Mechanical Stresses On The Dielectric Breakdown Strength Of GF/EP Composites

The glass fiber/epoxy(GF/EP)composites have been widely used in motors,winding insulation dry-type transformers,dry-type air-core reactor and other high-voltage electrical equipment because of the high mechanical and dielectric properties.The operation of power equipment is directly related to the safety and stability of the power grid,and the reliability of power equipment depends largely on the insulation.If the breakdown occurs on the insulation,it will cause immeasurable harm to the entire system.It can be seen that the breakdown characteristics of composite materials is an important index to evaluate the degree of composite insulation.With the level of the power system increases,the reliability of power supply system requirements are also increasing.To ensure the normal work of insulation under high voltage is very important.The insulation in the high-voltage electrical equipment is not only affected by mechanical stress such as vibration and impact,but also under the effect of electric and thermal stress.Therefore,it is important to research the effects of temperature and mechanical stress es on the dielectric strength of GF/EP composites,which have great significance to improve electrical strength and structure of the power equipment.The structure of GF/EP co mposites consists of resin matrix,glass fiber and interface.And the breakdown principle of GF/EP composite is very complex.A lot of experiments have been carried out on the breakdown properties of composite.However,there is no relevant research report on the dielectric strength under the combined operation of ambient temperature and mechanical stress of the power equipment.Because of the larger temperature difference,the phenomenon of malfunction is more frequent in the northeast of China.Therefore,it is important to study the dielectric strength of GF/EP composites under a wide temperature range.To research the effects of temperature and mechanical stresses on its dielectric strength,the AC breakdown test have been carried out on the GF/EP composites under different temperatures ? different stress magnitude and different style of the stresses.The results show that: under certain temperatures the dielectric strength decrease with increasing tensile stress;and the dielectric strength increase at first with increasing bending stress,reach a maximum and indicate a decreasing tendency thereafter;compared to room temperature,the dielectric strength of the GF/EP composites have been increased in different level under certain stress.The results provide important experimental basis for GF/EP composites in the practical application.