AC Breakdown Characteristics of Hybrid Nitrogen-Barrier Insulation Systems at Different Pressures

Breakdown voltage of the nitrogen insulation gap can be increased by inserting a polymer barrier to form a hybrid nitrogen-barrier insulation system. In this article, the effect of barrier position on the breakdown voltage of a hybrid insulation system is investigated at different gas pressures. Reducing the distance from the barrier surface to the rod electrode leads to higher breakdown voltages at gas pressures in the range of 0.1-0.25 MPa. Additionally, the breakdown field strengths of the insulation gaps at different gas pressures are studied. When the barrier is placed near the plate electrode, the breakdown field strength shows a linear increase with increasing gas pressure. Furthermore, the breakdown paths in the hybrid insulation systems can be classified into two types. The breakdown voltages of the two path types are close. A prediction model of the breakdown voltages at different pressures based on the breakdown path is proposed. The proposed model is also suitable for hybrid insulation systems with different size barriers. The barrier with lower relative permittivity and higher resistivity tested in this article has a more significant effect on increasing the breakdown voltage. The influences of the barrier surface charge on the electric field and breakdown processes are also discussed.