The vast majority of the high and extra high voltage projects under the ENTSO-E 2018 10-Year Network Development Plan (TYNDP) is planned using High Voltage Direct Current (HVDC) land and submarine cables and systems. Hence it is of critical importance for Europe future security of electricity supplies that HVDC cables and systems fulfil the highest reliability requirements at all times.
MI cables and systems are mature up to voltages of 525 kV and available up to voltages of 600 kV. Extruded HVDC cables and systems have seen a significant development in recent years: Voltage levels of 320 kV up to 640 kV are now available and as suppliers and TSOs are gaining operational experiences, the maturity and “Technology Readiness Levels” are increasing.
Recently an increased roll out of HVDC projects across Europe, many in the adverse offshore environment, has emphasised the significance, and concern for the availability of HVDC cables and systems. Even though the reliability and availability of worldwide HVDC systems have increased during the last decade, there is room for further improvement. HVDC systems are strategic assets within high voltage electricity transmission networks, their availability is therefore considered essential. Impact of HVDC system failures can result in significant consequences in terms of costs and electricity supply. However, the critical features and benefits that HVDC systems provides to the European system, such as support of system stability, sharing of spinning reserve (emergency power), boosting adjacent AC systems’ capacity, and inherently with low loss transfer, should also be considered when assessing the optimal solution for the transmission system. These additional features make it even more crucial to prioritise and value a very high level of reliability for the HVDC systems.