Within this work, a system for remote powering of small-scale hovering Unmanned Aerial Vehicles is developed, aiming to achieve prolonged-endurance flight times in order to address possible civilian applications with such requirements. To this purpose, the key-concept of a Power-over-Tether system is proposed, with the power bank for the UAV's operation located on the ground, and power transferred via a tethering cable. In order for the UAV to be capable of executing hovering trajectories as freely as possible, a long power cable is wound onto a custom-developed base, which is capable of releasing and retracting it when necessary. The Power-over-Tether system base is developed to operate autonomously, locally sensing when the aerial vehicle requires additional length of free cable to move to its intended goal, or when excessive cable length requires retraction, and performs the respective actions. The complete implementation of the system, both hardware and control-wise is elaborated in detail within the scope of this paper. Additionally, experimental evaluation studies are conducted, demonstrating the potential of the proposed Power-over-Tether system.