There are many thousands of miles of high power line transmission cables dispersed around Europe. Some are installed in remote areas where it’s difficult to serve. Furthermore, line cables operate in severe conditions. The cables are subject to many environmental and operation factors such as moisture, voltage stress, omitting jacking and structural imperfections.These factors are the main reasons for inducing defect within the cable structure. A common type of defect that has been identified as water trees, which are the resultant of elevated voltage stress combined with the moisture ingress into the cable structure. Hence, there is a need for Non-Destructive Testing (NDT) inspection technique that can detect common types of defects.The most widely used NDT techniques to detect defects in cables are visual inspection and helicopter missions. Visual inspection done by experienced teams of personal on foot, this usually takes a lot of time and effort and in some situations it is impossible to conduct due to the lack of accessibility.The helicopter missions can be used in such situation; however, it’s a very costly, tedious and difficult task, especially for the pilot since the helicopter needs to fly at minimum distance to the power lines. The possibility of strong side winds additionally turns this task into a dangerous situation.It is proposed to use Long Range Ultrasonic Testing (LRUT) as an NDT technique. LRUT can be used to inspect for defects/corrosion for many metres (up to 300m) from limited points of access. This technique will be used to identify the presence and the location of the defect (including areas where accessibility is an issue). This development will have a significant positive impact on the power industry as it enables just-in-time maintenance, reduction in the operation and maintenance costs, improving safety by reducing or eliminating helicopter line inspection and improve the quality of visual inspection practices commonly used today.