1. School of Electrical and Automation Engineering, Hefei University of Technology, Hefei 230009, China
2. Institute of Energy, Hefei Comprehensive National Science Center, Hefei 230031, China
3. Engineering Laboratory of Power Equipment Reliability in Complicated Coastal Environments, Tsinghua Shenzhen International Graduate School, Tsinghua University
4. State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China