The tri-post insulator is a core component within the gas-insulated transmission lines (GIL)

providing both electrical insulation and mechanical support. Typically

it is high-temperature cured through vacuum casting of a mixture of epoxy resin

curing agent

and alumina fillers. In recent years

frequent incidents of mechanical cracking and breakdown of tri-post insulators have been reported

which are attributed to residual stress concentration. However

the formation mechanism and distribution characteristics of the residual stress remain unclear. This study focuses on the curing kinetics and residual stress modelling of GIL tri-post insulators. It is verified that the epoxy resin/alumina reaction system follows the autocatalytic curing kinetic model by differential scanning calorimetry tests

and the model fitted by Malek's method corresponds well with the experimental results. Based on the Cure Hardening Instantaneously Linear Elastic model and the density inhomogeneity

it is found that a tensile stress concentration with a maximum value of 58.9 MPa at the edge of the insulator/sleeve interface

due to the mismatch of chemical and thermal shrinkage effects. Besides

the filler sedimentation can decrease the coefficient of thermal expansion and suppress the residual stress concentration. The investigation would help with the visualisation of the residual stress distribution in GIL tri-post insulators and provide some guidance for their processing treatments.