1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong UniversityXi'anPeople's Republic of China
2. China Electric Power Research InstituteBeijingPeople's Republic of China
3. Department of Electrical EngineeringTsinghua UniversityBeijingPeople's Republic of China
4. Laboratory of Advanced Technology of Electrical Engineering and Energy, Graduate School at Shenzhen, Tsinghua UniversityShenzhenPeople's Republic of China