Effect of Insulation Thickness on Space Charge and Electric Field Distribution in ± 500 kV HVDC Extruded Cables

This study concentrates on the effect of insulation thickness on space charge and electric field distribution in
$\pm 500 \text{kV}$
HVDC extruded cables. The modified bipolar carrier transport model (bipolar electronic-ionic carrier transport, BEICT) was used to emulate the dynamic evolution of space charge and electric field inside the insulation at temperature gradient
$(\Delta \mathrm{T})$
. The results show that the rise of
$\Delta \mathrm{T}$
intensified the homo-electronic charge injection on the internal side of insulating layer as well as dissociation of impurities, leading to massive hetero-ionic charges accumulating on the external side. The electric fields at the internal and external sides of insulating layer were thus weakened and strengthened, respectively. The increase in insulation thickness resulted in a higher
$\Delta \mathrm{T}$
along the insulating radial direction, exacerbating the electric field non-uniformity degree. Regarding
$\pm 500\text{kV}$
HVDC cable, 26 mm is a more appropriate choice, which not only ensures the safe operation, but also maximizes the insulation utilization.