1. School of Electrical Engineering, State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China
2. School of Electrical Engineering, State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, Shaanxi, China
3. Department of Electronics and Nanoengineering, Aalto University, P.O. Box 15500, Espoo, Finland