High Voltage (HV) overhead power lines are systems of interconnected elements that deliver massive amounts of electrical energy over long distances. Electrical conductors, used as energy carriers, are designed according voltage, current, and temperature rated value. Monitoring the power line's state variables is emerging as a crucial topic aiming at both determining the optimal real-time capability and defining a suitable model for Health Index assessment. A Wireless Sensor Network (WSN), consisting of many distributed sensor nodes that communicate with each other, can be a suitable tool to improve line ampacity by maintaining the operating variables in respect of their rated values. This paper investigates the design of an Energy Management System (EMS) for a wireless sensor for HV power line application and proposes a maximum power point tracker (MPPT). The behavior of the MPPT is discussed in terms of electromagnetic field laws and properties of magnetic materials. Ordinary and extraordinary operating conditions are investigated. The theoretical results are validated through a series of experimental tests. A prototype has been realized and tested for real operating currents. The tests are also used to verify the sensor's resilience in the presence of harsh fault conditions.