Parameter Design of Functionally Graded Materials for Tri-Post Insulator in HVDC GIL Under Stationary and Transient Conditions

This article conducts a simulation study on the parameter design of the superficially nonlinear-conductivity material (SNCM) and the permittivity functionally graded material (
$\varepsilon $
-FGM) for regulating the electric field distribution around the tri-post insulator in high-voltage direct-current gas-insulated transmission lines (HVdc GILs). The SNCM insulator is designed to adaptively relax the electric field distortion under variable voltages and temperatures while controlling the surface power loss within a proper range. The
$\varepsilon $
-FGM insulator aims to reduce the electric field strength under the polarity reversal voltage. By optimizing its permittivity gradient between 3 and 12, the maximum electric field after polarity reversal is decreased by 24.6%. The multidimensional functional material (MDFM) consists of the SNCM on its surface and the
$\varepsilon $
-FGM in its bulk, combining their advantages in regulating the electric field under both stationary and transient conditions. Compared with the SNCM insulator, the MDFM insulator has comparable electric field optimization effects but much lower surface power loss by two orders of magnitude.