Phase-change cooling technology is gradually applied in high-voltage power electronic equipment due toits suitable physical properties and insulation characteristics

which reveals excellent cooling capacity in the applica-tion. However

the insulation ability under the boiling refrigerant environment should be guaranteed to promote thecooling application in the high-voltage condition. In order to explore the boiling effect on the threshold of PD（partialdischarge）and the discharge characteristics under the boiling phase

the point-plain geometry is used to simulatethe non-uniform field distribution in the power electronic equipment. Then

the PD test platform is set up with the50 Hz AC insulating test system. Based on the methods of the PRPD spectrum and the statistical analysis

the partialdischarge inception voltage and the PD characteristics under the static state and the boiling state are compared. More-over

we get the PD characteristics of the bubble and the development of the bubble effect within the test voltagerange. Studies show that the insulation ability is reduced with boiling. However

the effect of boiling on the PD onlyappears during a certain voltage range because of the electric force acting on the bubbles.