1. State Key Laboratory of Electrical Insulation and Power Equipment and Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China
2. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry Chinese Academy of Science, Changchun 130022, China
3. Electric Power Research Institute, Yunnan Power Gird Co., Ltd., Kunming 650217, China