1. State Key Laboratory of Electrical Insulation for Power Equipment; Xi'an Jiaotong University; No. 28, Xianning West Road Xi'an China
2. Nanjing Power Supply Company; Nanjing 210019 Jiangsu China
3. Shaanxi Electric Power Research Institute; Xi'an 710054 Shaanxi China
4. Shaanxi Electric Power Corporation Economic Research Institute; Xi'an 710065 Shaanxi China