67 million people in the southern states of Brazil in January 2002 were left under a power blackout due to a failure of 460 kV conductors. Investigation showed that the external aluminum layer of the ACSR conductor was fractured, showing static deformation marks and dynamic fretting wear tangential marks. A reliable and fast NDT inspection with a UV camera proved to be efficient in identifying deformations on conductors, alerting them before imminent shutdown.

Overhead transmission line conductors form the backbone of the energy distribution grid. Throughout their service, these conductors must sustain the cumulative effect of both environmental, mechanical and voltage stress. Environmental factors include wind induced vibrations, galloping in response to wind gusts, icicles, melting ice, lightning strikes, pollution, algae, etc. Mechanically, conductors must be able to sustain the high temperature resulting from Joule heating without excessive thermal expansion and withstand the stresses of ice and wind loading. Electrically they are designed to maximize the current capacity by optimizing the electrical conductivity within the mechanical constraints.

To complicate things even more, often and without any warning, it turns out that there are innate structural imperfections due to faulty manufacturing, not to mention bad workmanship where conductors are being dragged during installation with their surfaces getting rough and brittle.

All those factors can result in structural failures such as loose earth conductors, twisted/ruptured/broken wires, corrosion and reduced mechanical and electrical ratings. Strong winds may cause the wear of various fittings in the transmission line system. The bearing capacity of the worn fittings will be greatly reduced and threaten the operation safety of the transmission line system.

Ofil’s DayCor® UV cameras are being used to alert maintenance teams of existing corona effects that are trigged by structural discontinuities, and to collect true images of the power line components for the sake of analysis, trending and predicting. Non-destructive Testing (NDT) techniques, such as Ofil’s have been widely used to provide pre-emptive measures against structural failures. However, the efficiency of these methods relies heavily on the quality of the acquired images, and thus on the quality of the camera. Indeed, Ofil’s corona cameras are well known for their highest quality, stability, accuracy and sensitivity. DayCor® users belong to the exclusive club of UV inspectors, which explains their loyalty.