Numerical Calculation Model for Obtaining Parameters of Insulation Materials in HVDC-GIL Subjected to Transition Field

In this paper, we compare the differences in the charge accumulation for two different models about conductivity: one in which the conductivity value of the spacer is invariant with time (steady-state conductivity, Model I) and one in which the conductivity value can vary dynamically with time (dynamic conductivity, Model II). The time for the potential distribution to reach a stable state is 8078 s in Model I and 7932 s in Model II. After the charge accumulation reaches saturation, the charges migrate to the middle of the spacer under the applied electric field. Maximum tangential field strength is 2.56 x 10(6) V/m in Model I and 2.84 x 5 C/m(3) , which is much smaller than the charge density in the spacer. The mechanism underlying the charge accumulation phenomenon is the differences in the conductivity value distribution caused by a time-varying temperature gradient field. This paper can provide a more precise theoretical basis for the selection and modification of HVDC-GIL spacer.