I. Introduction
Our society is becoming increasingly more dependent on reliable electric power supply. Since power outages cause substantial financial losses to the producers, distributors and also to the consumers of electric power, it is in the common interest to minimize failures on power lines. To detect the defects early and to accordingly schedule the maintenance activities, the distribution networks are inspected regularly. Inspection of overhead power lines is usually done manually, either directly on the lines or indirectly from the ground and/or from the helicopters. All these tasks are tedious, expensive, time consuming and dangerous. Consequentially, more and more research has been focused on automating the inspection process by means of mobile robots that would possibly surpass the abovementioned disadvantages. Namely, robot-assisted inspection could be carried out faster, cheaper and more reliable, thus improving the long-term stability and reliability of electric power supply. Most importantly, the safety of the inspection workers could be increased significantly.