Low voltage DC cable insulation challenges and opportunities

This paper addresses the challenges arising when considering the conversion of an existing low voltage cable infrastructure in distribution networks from AC to DC. It will explore the ageing mechanisms of low AC voltage cable insulation and how could they differ when operated at DC voltages. In a DC environment, the cables may experience lower voltages but higher currents; hence the thermal ageing could be the dominant stress component that may determine the lifetime of DC cables. A model based on a campus distribution network is used to identify possible constraints. Existing AC cables and their characteristics (based on a 6.6 kV distribution network), such as ampacity, temperature-current characteristics, power requirements of the system and simulation results for cables at different loads are investigated. Properties affected by ageing under AC conditions for the existing cables are considered along with constraint-points of the network.