Fig. 1. Schematic diagram of partial discharge initial voltage (PDIV)and insulation breakdown voltage test apparatus

Fig. 2. SEM images of the surfaces and interface of PTFE/PP composite insulation with different apertures

Fig. 3. Polarization properties of PPLP and PTFE/PP composite insulation in LN₂ at 50 Hz

Fig. 4. Comparation of the partial discharge inception voltage between PPLP and PTFE/PP in LN₂

Fig. 5. Conversion of composite insulation system to separate material combination

Fig. 6. Breakdown strength of PPLP and PTFE/PP in LN₂