1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, 28 Xianning West Road, Xi’an 710049, China
2. School of Electronics and Information, Xi’an Polytechnic University, 19 Jinhua South Road, Xi’an 710048, China
3. State Grid Shandong Electric Power Company Electric Power Research Institute, 2000 Wangyue Road, Jinan 250001, China