<p>With the rapid development of smart grid, more and more sensors are used to monitor high voltage direct current (HVdc) transmission lines to ensure safe and stable power delivery. However, powering these sensors sustainably is a significant challenge. This paper introduced an energy harvesting method based on corona discharge to supply sustainable power to the sensors in HVdc transmission lines. The significant advantage of this method is that the energy comes from the transmission line itself, unlike the traditional methods that the energy comes from external sources such as solar photovoltaic and wind power. Sustainable power comes as long as the HVdc transmission line is charged with high voltage and corona discharge occurs, unlike the energy harvesting device of current transformers relying on AC magnetic fields for energy exchange, which subject to the line currents or loads. Firstly, this paper proposed a resistance–capacitance equivalent circuit of micro energy harvesting based on corona discharge and theoretically analyzed the relationship between the energy and some factors influencing factors, such as voltage, its polarity, and the leakage of energy storage components. Furthermore, an experimental platform based on energy harvest from corona discharge was established to verify the influence of the above factors on energy-harvesting. Finally, it is found that a transistor with negative resistance characteristics can be used as a power electronic switch to successfully control the LED lamp, demonstrating the production of stable pulse electric energy from corona discharge for certain specific loads.</p>