The utility model relates to a drainage device in the high tension cable trench, especially a high tension cable connects high -power induction electricity -taking of well and exchanges automatic water discharging device, its structural feature lies in, still including induction electricity -taking circuit and water discharge control means part, the induction electricity -taking circuit is including current transformer, electric power board, rectifier module, direct current conversion module and the energy storage module connected according to preface electricity, and wherein the current transformer joint is on high tension cable, the water discharge control means part is including dc -to -ac converter, control circuit and floater, the dc -to -ac converter is connected to the output of energy storage module, and the control end and the control circuit of dc -to -ac converter are connected, and the output and the water draining water pump electricity of dc -to -ac converter are connected, and the floater is then connect control circuit's switching signal input. The utility model discloses a CT mutual -inductor induction electricity -taking storage of joint on high tension cable willbe stored electrical energy conversion through the dc -to -ac converter and drawn water with the working shaft. The scene need not to lay the low tension cable, has both saved the cost, has reduced the potential safety hazard simultaneously again.