1. Department of Mechanical Engineering, Hebei Provincial Key Lab of Electric Power Equipment Maintenance and Failure Prevention, North China Electric Power University, Baoding 071003, China
2. State Grid Beijing Electric Power Research Institute, Beijing 100000, China
3. Department of Electrical Engineering, North China Electric Power University, Baoding 071003, China
4. Department of Electrical and Electronics Engineering, University of Nottingham, NG7 2RD, Nottingham, UK