The current research of suppressing secondary arc current in the world is introduced.The mechanism of secondary arc current and the suppression methods are analyzed.The structure and fundamental principle of extra-high voltage controllable reactor are also analyzed.According to the four-radial compensation method of shunt reactors

the formulae for selecting neutral grounding reactor are listed.Based on the electromagnetic transient program（EMTP）

simulation models of EHV controllable reactor and 500 kV transmission line from Sanyou to Jiangling are built up.And numerical simulations are performed to verify the effectiveness of suppressing secondary arc current.The results demonstrate that the controllable reactor can suppress secondary arc current effectively in EHV transmission line.