Towards Enhanced HVDC Cable Systems

Lead Research Organisation: University of Southampton
Department Name: Sch of of Electronics and Computer Sci

Abstract

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.

Planned 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.
 
Description This project has completed. We have published 20 papers at international conferences and in journals. We have developed several experimental systems such as space charge measurement with temperature gradient, cable PEA system that allow us to investigate charge dynamics in PPLP laminated cable insulation. A PPLP lapping device has also been developed that makes model cable with PPLP insulation possible. In addition, we also established an oil impregnated system that is essential for mimic industrial process.
Space charge results from layered PPLP structure explain why the PPLP insulation can achieve better electrical performance. The polarity reversal results demonstrate that such operation is not desirable for PPLP laminated insulation. We have shared this finding with the National Grid and other industrial panel members. Through our work there is renewal interests in PPLP insulation for HVDC cables. An invited plenary lecture was delivered at IEEE ICPADM 2018.
The effect of mechanical bending/force on DC partial discharge measurement has been successfully performed on PPLP lapped insulation.
Electrical treeing observed for layered structure revealed the role of interface in the growth of electrical tree under both AC and DC conditions.
Exploitation Route An expert panel from the UK electrical power industry attended our progress meetings regularly. National Grid, Mutual Energy and H&R ChemPharm are particularly interested in our findings.
Through our publications and reporting at international conferences, we have observed a renewed interests in PPLP insulation cables. For example, we have been contacted by researchers in China and South Korea to develop research collaboration.
Sectors Energy

 
Description Our findings have been channelled to UK industries through our quarterly progress meetings (Industrial advisory panel members have been invited to attend). The impact of oil on charge distribution in PPLP insulation has been reported to H&R ChemPharm and the impact of space charge on polarity reversal of oil/impregnated HVDC cables to Mutual Energy.
First Year Of Impact 2018
Sector Energy
Impact Types Economic

 
Description DC networks, power quality and plant reliability
Amount £727,155 (GBP)
Funding ID EP/T001232/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 07/2019 
End 01/2023
 
Title Electrical Tree Web site 
Description A place where our imaging work can be obtained 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Hopefully researchers form around teh world can use this as data for their work. 
URL https://www.manchestertrees.com/
 
Description 2016 IEEE Electrical Insulation and Dielectric Society Workshop (Toronto) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Establish the existing knowledge on high voltage direct current cables and discuss future research activities/direction.
Year(s) Of Engagement Activity 2016
 
Description CEIDP Conference (Toronto) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Research progress in general dielectric materials.
Year(s) Of Engagement Activity 2016
 
Description Conference on Electrical Insulation and Dielectrics (USA) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This is an annual conference organised by IEEE DEI society to report ongoing research findings. It has been well attended by researchers across the world.
Year(s) Of Engagement Activity 2015
 
Description ICD Conference (Montpellier) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Research progress in dielectrics.
Year(s) Of Engagement Activity 2016
 
Description Invited plenary lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact An invited plenary lecture was delivered at an IEEE International Conference (ICPADM) where the audience often comes from research institutes and industries. For the first time, the electrical performance of PPLP insulated HVDC cables has been explained. It highlights the importance of the interfaces between PP and Kraft paper. With the growing interests in HVDC cables due to renewable energy, PPLP provides an alternative solution, especially for higher level DC voltage.
Year(s) Of Engagement Activity 2018