For the UK to meet legally binding renewable targets by year 2020 and beyond, a series of wind farms are under construction, and more new projects are being developed. The offshore grids and their connection to the existing transmission systems can only be realised using the HVDC links. Using high voltage will make power transmission more efficient and the only feasible solution is to use extreme upgrades to existing plant. Cables, the key part of the HVDC links, will be forced to operate well beyond their existing limits (currently about +/-500 kV and 1000 MW). This means that both cable insulation and operating conditions have to be pushed far beyond the limits currently considered acceptable. Therefore, a fundamental understanding of the performance of the insulation and the development of novel operating methodologies are urgently required to meet the challenges. This project will investigate the impact of inherent defects, space charge dynamics, partial discharges, electrical tree and power quality on electrical performance of highly stressed lapped cable insulation and develop novel operating methodologies that take account of the influence of the above factors to achieve reliable and safe operation for the HVDC links.

Potential Impact:
In addition to the academic environment, this research project has been designed to have a direct impact on power transmission operators as the research addresses the fundamental issues related to efficient and reliable HVDC cable systems. To use extreme upgrades to existing plants or develop next generation of HVDC cables, it is imperative for the operators to understand charge dynamics and degradation processes in the cable insulation system provided by this research. It will allow HVDC cable system to be operated in its optimal condition without worrying about insulation overstressing.

The research also provides novel operating methodologies that allow HVDC transmission system operates according to its environmental conditions.

The research addresses fundamental issues related to efficient and reliable operation of HVDC cable system. Resilience and reliability of power supply is essential to the UK economy. More importantly, HVDC transmission systems are an essential part of the offshore grids which are closely related to the renewable generation and the UK government policy energy security and climate changes.

The research will have a significant global impact. All four Work Package leaders are heavily involved in international activities through learned societies and through CIGRE. We will use these routes to engage with a wider audience and disseminate our research outcomes.