Manual outage-free maintenance of electrical power lines is conducted in order to fulfil the increasing demand of uninterrupted power supply. In these techniques care regarding hazard of electric shock and falls must be exercised while the work is performed on or near energised elements. In order to increase the safety and comfort of the workers as well as the overall efficiency, a teleoperated system for live-line maintenance, called ROBTET, has been developed for the electrical utility IBERDROLA. The ROBTET and its advanced features are described in detail in this paper. Special emphasis is made on the virtual force field system developed to protect the manipulators from provoking a shortcut while working near the lines. It makes use of a computer model of the environment and of the force reflecting capabilities of the master arms.