In order to study the repeated flashover characteristics of polybutylene terephthalate (PBT)

repeated flashover experiments were carried out on PBT thin film samples to study the characteristics and causes of flashover voltage changes. Five groups of PBT thin film samples were prepared

and surface flashover experiments were carried out on the five groups of samples under power frequency AC voltage for 0

100

200

300

and 400 times

respectively

and the flashover voltage of the samples was recorded. Scanning electron microscope

laser confocal microscope

infrared spectrometer

differential scanning calorimeter

electric stimulation depolarization current meter and surface potential meter were used to detect the surface microstructure

roughness

chemical structure

crystallinity

trap parameters and surface potential of the samples. The test results show that the surface flashover voltage of the PBT sample increases first and then decreases with the increase of flashover times

and reaches the maximum value when the flashover is 100 times. Before 100 flashovers

the sample becomes smoother with the increase of flashover times

the surface crystallinity increases

the deep trap density decreases

and the energy level decreases. After 100 flashovers

as the number of flashovers increases

microcracks and holes appear on the sample surface

the surface crystallinity decreases

the deep trap density increases

and the energy level decreases. Analysis shows that the repeated flashover characteristics of PBT surface are closely related to the cumulative damage on the surface of the material. Cumulative damage leads to changes in roughness and trap parameters

which in turn lead to changes in surface electric field distribution and flashover voltage.