College of Technology&Engineering;
Yangtze University;
Jingzhou 434023;
Hubei;
China;
State Grid Hubei Electric Power Research Institute;
Wuhan430077;
Hubei;
China;
School of Electrical and Electronic Engineering;
HuazhongUniversity of Science and Technology;
Wuhan 430074;
Hubei;
China;
streamer branch; orthogonal optical observation; streamer inception; branch type; branch angle; optical diameter of streamer branch;