Multi-modified epoxy insulation with improved flashover threshold for HVDC applications

The flashover threshold (V_flsh) of polymer insulations such as epoxy (EP) in HVDC systems can be augmented by modifying their surface with an appropriate treatment technology. For such purpose, several surface treatment methods such as ion beam, sandpaper and a combination of the two is introduced. Firstly, insulation samples with pure epoxy (EP_pure), different ion beam treatment periods (EP_ion;10, 15, 20 min) and different roughness (EP_sand; R1 = 4.23 μm, R2 = 6.34 μm, R3 = 9.21 μm) are prepared on the laboratory scale. Afterward, based on several characterisations, such as surface conductivity, mean surface roughness and potential distribution of these insulations, multi-modified insulation (EP_multi = EP_ion-20 + EP_sand-R3) is prepared. In the end, the V_flsh of each insulation group is measured and compared to examine the effectiveness of the proposed modifications. It is obtained that the V_flsh of the modified insulations augmented dramatically irrespective of the treatment method. The V_flsh of the insulation group EP_multi augmented by 52.66 % which is the highest improvement among all insulation groups. In short, the proposed surface modifications are effective and could be used as references to enhance the insulation strength of polymer dielectrics in HVDC systems.