1. State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
2. LAPLACE (Laboratoire Plasma et Conversion d'Energie), Université de Toulouse; CNRS, UPS, INPT; 118 route de Narbonne, F-31062 Toulouse, France