Assessment of Thermal and Electric Field Characteristics of HVDC Cable According to the Inner Filler Size of XLPE

Increasing the rating of the HVDC cable causes an inevitable increase in the heat generated inside cable. Thus, it is necessary to improve the thermal conductivity of the Cross-linked polyethylene (XLPE) insulation material used in the extruded cable for effective thermal management. Also, several methods have been pro-posed so far to increase the thermal conductivity of XLPE. However, the influence of the filler addition on the thermal conductivity has been mainly studied experimentally so far. Therefore, numerical analysis was performed to investigate the effect of filler size and its content on thermal conductivity of XLPE. In the modelling of XLPE composite for numerical analysis spherical Al2O3 particles with a radius of 25, 50, 100 and 200 nm were considered. Additionally, filler contents were considered with up to 20 wt%. Numerical analysis of XLPE composite model showed that the effective thermal conductivity increased with the smaller filler size. Also, as the content of filler increased, the effective thermal conductivity increased. A coupled electro-thermal model considering the previously derived thermal conductivities was used to investigate the influence of the thermal conductivity of XLPE on temperature and electric field distribution. From the simulation results it can be concluded that, higher thermal conductivity of XLPE can reduce the thermal and electrical stress of the cable. Therefore, it is considered that the smaller the size of the filler added to the insulation or the larger the content of the filler, the thermal and electrical stress in the cable can be reduced.