In order to reveal the influence mechanism of temperature on the discharge degradation of epoxy-polyimide casting interface under high-frequency square-wave voltage

we construct a composite insulation interface model based on the actual working condition of Potting process

and build a test platform of casting interface discharge by combining the silicon photomultiplier tube and UHF to study the interface discharge characteristics of casting interface of epoxy-polyimide composite insulation under different temperatures and high-frequency square-wave voltage. The results show that

when the temperature rises from 25 ℃ to 150 ℃

the onset voltage of interfacial discharge decreases by 26.98%

the maximum discharge amplitude increases by 1.78 times

the average discharge amplitude rises from 203.4 mV to 546.7 mV

and the total discharge frequency increases by 172.4%; meanwhile

the temperature rise leads to a significant backward shift of the discharge phase. The mechanism of temperature influence on the discharge characteristics of casting interface is further analyzed according to the debonding effect of the interface

and it is clarified that the temperature rise affects the electric field inside the void through the synergistic effect of accelerating the interfacial charge relaxation and regulating the spatial distribution of the residual charge

leading to the increase of the number of discharges and the amplitude

and the backward shift of the phase of the discharges. The research results provide a certain theoretical basis for the matching of thermodynamic parameters of high-frequency transformer insulating materials

the control of defects in the casting process and the setting of operating temperature threshold.