Breakdown Process Modeling of Tri-post Insulator Subjected to Electrical and Mechanical Loadings in HVAC-GIL

In this study, a simulation model is established to study the breakdown evolutions of the tri-post insulator under the combined effects of electrical and mechanical stresses. External forces of different values and in different directions are applied to the insulator in addition to an AC voltage of 1100 kV. Results show that after applying electrical stress and straight tension along the insulator post, the tensile stress and the corresponding strain energy density are concentrated around the tips of the lateral branches, thus promoting their expansion, and even causing a transverse fracture under the condition of 100 kN. In the case of a small straight compression below 25 kN, the breakdown process can be restrained. But when it comes to 75 kN, the breakdown process is promoted again, and a shear fracture can be caused above 100 kN. The outcomes of this study are hoped to help understand and predict the breakdown behaviors of dielectric materials.