MU Haibao was born in Hebei Province, China, in 1982. He received the B.E. and M.E. and Ph.D. degrees in electrical engineering from Xi'an Jiaotong University, Xi'an, China, in 2004, 2007 and 2011, respectively. From 2009 to 2010, he was a visiting researcher in Tokyo City University, Tokyo, Japan. Since 2011, he has been a lecturer with Xi'an Jiaotong Univer- sity. His research interests are electrical breakdown phenomena of dielectricsE-mail: haibaomu@mail.xjtu.edu.cn WANG Da was bom in Heilongjiang Province, China, in 1987. She received the B.E. degree from the College ot Electrical & Electronic Engineering in Harbin University of Science and Technology, Harbin, China, in 2010. Currently, she is pursuing the Master's degree in the School of Electrical engineering, Xi'an Jiaotong University. Xi'an, China. Her research interest is diagnostics of power transformer insulation E-mail: wangda198721@126.com