Updated Review of the Life and Reliability Models for HVDC Cables

This paper updates previous reviews of life and reliability models for HVDC cables. The update is motivated by the impressive R&D activities on HVDC cable systems in the last years, with many projects at increasing levels of voltage and power; this makes the sound evaluation of life and reliability of HVDC cables crucial. Physical and phenomenological life models proposed over the years for constant electrical and thermal stresses are reviewed first, including the relevant probabilistic framework and the effects of cable insulation volume enlargement. Then, more recent procedures for life and reliability estimation under time-varying electro-thermal stress are reported, focusing on thermal transients due to load cycles and voltage transients due to long Temporary Over-Voltages, Superimposed Switching Impulses and Voltage Polarity Reversals. Results of the application of such procedures are also presented, with a discussion on their limitations, and on open issues.