An energy acquisition system for the ground wire of an overhead transmission line can provide a continuous and stable power supply for an on-line monitoring device. Its key issue is how to obtain enough power. To solve this problem, an energy acquisition scheme based on the double-insulated ground wire of an overhead transmission line has been investigated in this study. Three energy acquisition schemes were proposed, equivalent circuit analysis models of the three energy acquisition schemes were established, and the maximum power acquired was theoretically analyzed. The energy acquisition power of the three energy acquisition schemes for different tower-type sizes was also analyzed. A simulation model was built in PSCAD. The effects of load impedance, length of energy acquisition wire, grounding resistance, and load current on the power acquired were analyzed. The research results of this paper provide theoretical guidance for choosing an energy acquisition scheme and for designing key parameters in practice.