The temperature rises during gas insulated transmission pipeline（GIL） operation will accelerate the aging of epoxy insulators

and the surface charge behavior of insulators under temperature gradient is also closely related to flashover. In order to solve the above problems

EP/BN composites with high thermal conductivity were prepared

of which the surface charge dynamics under needle-plane corona system were investigated with different cooling time after being heated to 60 ℃. The results show that the surface charge dissipation rate of the sample decreases first and then increases with increasing the BN contents at the same temperature

and the initial surface charge density increases first and then decreases. For the same sample

the surface charge dissipation slows down and the initial surface charge density increases with the lapse of the cooling time. Besides

it can be found from the trapping distribution characteristics that the depth of both deep and shallow traps becomes lower

and the deep trap density increases while the shallow trap density decreases. The higher the BN content is

the more obvious the distribution characteristics are.