1. College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
2. Research Institute for National Defense Engineering of Academy of Military Sciences, Luoyang, Henan 471023, China
3. Pinggao Group Co., Ltd., Pingdingshan, Henan 467000, China
4. State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China