Fig. 1. High voltage insulation test platform

Fig. 2. The experimental chamber for liquid surface flashover in the load region

Fig. 3. liquid surface flashover experimental chamber and electrode assembly

Fig. 4. Simulation structure and finite element parameter settings

Fig. 5. Simulation results of electric field

Fig. 6. Typical flashover voltage waveforms

Fig. 7. Comparison of flashover voltage waveforms between self-breakdown mode and trigger mode

Fig. 8. Curves of flashover voltage U_f and flashover field strength E_fvs sample thickness h

Fig. 9. Discharge channel ablation traces

Fig. 10. Fractured PMMA samples

Fig. 11. Flashover voltage waveform (different voltage application time)

Fig. 12. Curve of flashover voltage vs voltage application time

Fig. 13. Samples of PMMA with different surface roughness

Fig. 14. Curve of flashover voltage U_fvs surface roughness R_a

Fig. 15. Flashover field strength fitting curve