The auxiliary devices must to be installed on high voltage transmission lines to improve capability of condition monitoring. Power supply for these devices is very difficult to provide. For lack of solar cell and induction power supply, a new kind of rechargeable induction power supply at high voltage side is designed. Device is composed by power module, power conditioning module, and intelligent protection module and charge management circuit of Lithium battery. Working principle and circuit of module are given. Data of device performance test is obtained after the experiment. Experiment shows that: the device is correctly and effectively, and it can provide security, ability, and uninterrupted power.