This paper is focused on the robotic application for electrical live power lines maintenance. These tasks are matters of great significance for utilities companies, since their goal is to achieve a good quality of service. The main features of these works are that: the tasks are carried out over live-lines up to 90 kV; the robots are teleoperated by human operator; and a vehicle to place the robots over the desired line is required. In this paper the main development of teleoperated systems for live-line are mentioned, and the ROBTET system is described on detail. This telerobot has been developed by the Universidad Politéc. de Madrid, in collaboration with Iberdrola and Cobra, Spanish utility and contractor respectively.