Considerations of nano-alumina-based polyethylene and polypropylene nanocomposites for HVDC insulation

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2023
Thesis identifier
  • T16569
Person Identifier (Local)
  • 201558737
Qualification Level
Qualification Name
Department, School or Faculty
  • Extruded polymeric insulation material has been widely used in high voltage alternating current (HVAC) power transmission system for a long time. Recent years, with the advent of renewable energy around world, more large energy capacity, long distance high voltage direct current (HVDC) transmission projects were developed. The quality of insulation materials of HVDC cables has become the most critical issue that restricts the development of HVDC transmission. Cross-linked polyethylene (XLPE) has shown superior electrical, thermal and mechanical properties due to its special cross-linked structure and has become the default material for HVDC cable insulation in the last few decades. But today, with the increasing concern of environmental protection and sustainable development, traditional XLPE cables are no longer the default for future HVDC applications due to its limited operating temperature, non-recyclable nature and high energy consumption in complex production process. Therefore, new thermoplastic polymeric insulation materials are being developed, which are recyclable and can be operated under higher temperature. However, these materials still have weak points like space charge accumulation. The incorporation of nanoparticles has been proven to be an effective method to overcome these drawbacks. In this study, thermoplastic polymers, polyethylene (PE) and polypropylene (PP), were selected as the potential matrix materials to study. Nano-alumina particles with and without surface modification were introduced into polymers at different filling contents to make nanocomposites. This thesis reports the comprehensive study on PE/nano-alumina composite systems and PP/nano-alumina composite systems. The surface chemistry of nano-alumina with and without surface modification was characterized by thermal-gravimetric analysis and Fourier-transform infrared spectroscopy. The morphological structure of nanocomposite systems was analyzed by using polarized optical microscopy and scanning electron microscopy. Electrical properties such as DC breakdown strength, DC conductivity, and space charge were investigated to evaluate the feasibility of the proposed nanocomposite materials as future HVDC cable insulation. A deep understanding of the effect of nanoparticles on the dielectric properties of polymeric nanocomposites was achieved. After comparing the performance of PE nanocomposites and PP nanocomposites, PP nanocomposites exhibit superior electrical properties and can be considered as the future alternative to XLPE. In conclusion, the experimental results and discussion presented in this project can contribute to the design and manufacture of recyclable polymeric nanocomposite materials for future HVDC applications.
Advisor / supervisor
  • Given, Martin J.
  • Siew, W. H.
  • Liggat, John
Resource Type