In order to solve the serious decline in resistance to tracking performance of epoxy roof insulator under discharge on EMU

on the basis of ANSYS

we establish a three-dimensional nonlinear transient electric and thermal coupling model of pantograph roof insulator in which discharge occurs along surface. Simulation results show that the tracking degree is characterized by temperature rise. When the insulator produces partial tracking

capabilities of resistance to tracking from low to high are the jacket surface

the up sheds surface

and the down sheds surface. When the flashover occurs on insulator

the maximum temperature is on the sheds edge and resistance to tracking capability the lowest

and the minimum temperature is on the sheds root

and resistance to tracking capability is the highest. The time of generating tracking is different

for example

time on shed surface is 0.14 s

jacket surface is 0.20 s

and shed down surface is 0.55 s. After generating tracking

the tracking has a nonlinear relationship with time. Eroded depth increases linearly. However

a double-exponential function can be used to represent the eroded width

which is slowed down and finally tends straight. Research results show the abilities of resistance to tracking and regularity of erosion on the different parts of epoxy roof insulator

which can provide the theoretical support to the safe operation of EMU.