This device operates on the principle of electromagnetic induction, directly sensing AC magnetic field energy from the cable using a power CT. The energy is then rectified, filtered, and stabilized to produce a stable and reliable DC voltage, which can provide a steady power supply for electrical equipment installed nearby. The device is divided into two parts: one for the electromagnetic induction power CT, and the other for the power conversion unit. It is suitable for providing a stable power supply for cable-based online monitoring products and electrical equipment for online detection, monitoring, patrol, and anti-theft on high-voltage transmission lines.