Temperature and Electric Field Profiles of Tri-Post Insulator in DC GIL Under Electric-Thermal Coupled Stresses

This paper presents a 3-D numerical modeling of electric field and temperature distributions in a tri-post insulator of DC (Direct Current) GIL under -400 kV. The simulation results indicate that in DC GIL chamber, the electric field strength distribution on the bilateral surfaces of the tri-post insulator increase from cylindrical wall toward the central conductor. The minimum electric field intensity is 1.0 kV/mm at the grounding wall side, whereas the surface site with the maximum electric field intensity of 6.0 kV/mm is within 1% of the total arcing distance away from the central conductor. The overall temperature distribution in the DC GIL chamber is always lower on the lower side than on the upper side, whereas the maximum temperature on the tri-post insulator is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$35.2^\circ \mathrm{C}$</tex> and the minimum temperature is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$11.9^\circ \mathrm{C}$</tex>, i.e., an obvious thermal gradient exists along the tri-post insulator.