I am Haoyu Gao, one of the winners of 2024 DEIS Graduate Student Fellowship. It is a great honor for me to have the opportunity to write this summary report for the DEIS Graduate Student Fellowship. Firstly, I would like to express my sincere gratitude to my supervisor Prof. Qingmin Li (North China Electric Power University) and to the DEIS Education Committee. Under the guidance of Prof. Li and the support of the DEIS Graduate Student Fellowship, I could complete my doctoral research successfully.
Then, I would like to introduce the conducted work under the DEIS Graduate Student Fellowship. My research primarily focuses on space charge measurement technology for solid dielectric materials. Based on picosecond pulse width terahertz excitation and elasto-optical sensing, I have proposed a novel space charge ellipsometry measurement method. Compared with the traditional charge measurement methods, the temporal and spatial resolution of the novel method has been significantly enhanced, reaching microsecond and micrometer level. Additionally, benefiting from the full-optical isolation between high and low voltage side, the space charge measurement could be carried out under high frequency complex electrical voltage.
Up to now, there are several research developments I would like to share. For the excitation side, the optimization method of terahertz generation with high electric field intensity is proposed. For the elasto-optical sensing side, the modified SU-8 photoresist-based elasto-optical sensor with hundred nanometer thickness is prepared. For the detection side, the ellipsometry sensitivity optimization method is proposed and charge measurement performance is evaluated. Finally, based on the developed terahertz generation module, elasto-optical sensing module and ellipsometry detection module, the space charge ellipsometry system is constructed. The experimental result shows that the constructed charge ellipsometry system could realize the insulation charge measurement with spatial-temporal resolution of 50 μs and 6 μm.
Space charge ellipsometry system
Meanwhile, with the support of the DEIS Graduate Student Fellowship, the related work had the chance to be presented at the CEIDP 2025, which was held in Manchester, UK. CEIDP provided an excellent opportunity for academic communication, allowing the work to be recognized by other scholars.
Poster presentation at CEIDP 2025
Finally, I would like to express my gratitude once again to the DEIS Education Committee. The DEIS Graduate Student Fellowship not only provided financial support but also broadened my academic perspective and strengthened my academic confidence. Additionally, it also provided an excellent opportunity for me to engage with experts and scholars from academia and industry. Exactly during the communication, I developed a keen interest in the development of EHV and UHV transmission equipment, so that after graduating from North China Electric Power University, I am going to join China Electric Power Research Institute as a R&D Engineer, still working in the field of high-voltage and insulation engineering.