Experimental Evaluation of high voltage insulated cables (220 kV) performance and ageing under N-X operation conditions

High voltage insulated power cables have proved high reliability and performance along their use in electrical grids. Lifetimes over 30 years have been achieved on cables and accessories. However, management of their remaining life is a question of paramount importance for reliability, availability of the power network and asset management. Some experimental works on accelerated ageing tests on cables show how the cable degrades. However, there are few data about which is the impact on cable health of an exploitation strategy where current overloads can be applied as long as the cable temperature does not exceed 90 °C (in XLPE insulated cables). This work shows a long term testing (3600 h) on a 220 kV insulated cable. A specific setup has been built for this study and some different non-standardized or real current profiles have been applied. Results show that the insulation of the cable resists such regimes without a significant ageing. However, at the end of the test some surface defects can appear although they seem not to be critical at all. And, additionally, some hot spots can also be produced in the accessories of the cable which may be monitored to control their evolution.