Nowadays, online monitoring systems are widely used in high voltage power transmission systems, leading to the requirement of reliable power supply units for the equipment. In this paper, we present a novel design to integrate planar printed circuit board (PCB) resonator coils into insulation string, so that the high voltage insulator can not only provides insolation between transmission line and transmission tower, but also offer the wireless power transfer (WPT) capability to power the online monitoring devices. Practical experiments have been conducted to confirm the feasibility and effectiveness of this new design. The new design also simplifies the work process in the mass production and improved the reliability of the resonators.