Improved ampacity of buried HVDC cable with high thermal conductivity LDPE/BN insulation

Abstract

Polyethylene is widely used as insulation in power cables with its excellent electrical properties except its low thermal conductivity. However, insulation-related thermal problems pose a limitation on the ampacity of HVDC cables. Improving the thermal conductivity of insulation may contribute to heat dissipation of cable system and enhance its ampacity. In this work, in order to investigate the effects of improved thermal conductivity of insulation on temperature field and ampacity in a single buried HVDC cable, a numerical simulation model is established by finite element method (FEM) and the cable ampacity is calculated by a modified iteration method. Meanwhile, a range of low-density polyethylene (LDPE) based composites filled with hybrid boron nitride (BN) particles at different loadings are prepared to get reasonable model parameters. Thermal conductivity of various samples is measured and the obtained result shows that the thermal conductivity of BN filled LDPE composite is improved greatly. The simulation results show that the cable core temperature is reduced obviously and the temperature field distribution in insulation becomes more uniform with increasing the thermal conductivity. Besides, the temperature difference between inside and outside of insulation layer shows a decreasing trend at a given load current. Namely, the cable can transmit higher current under the maximum operating temperature due to the improvement of thermal conductivity. All the conclusions imply that the improved thermal conductivity of insulation is of great benefit to the improvement of HVDC cable ampacity.