1. Xi’an Key Laboratory of Electrical Equipment Condition Monitoring and Power Supply Security, College of Electrical and Control Engineering, Xi’an University of Science and Technology, Xi’an 710054, P. R. China
2. State Key Laboratory of Electrical Insulation and Power Equipment, Center of Nanomaterials for Renewable Energy, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049, P. R. China