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Non-Destructive Structural Inspection of Transmission Lines

5 October 2015by admin
by V. Almeida, J. Gomes-Mota, S. Matias; Albatroz Engenharia
accepted to publication at the International Conference on Condition Monitoring, Diagnosis and Maintenance – CMDM 2015, 5-8 de Outubro, 2015, Bucareste, Roménia, cmdm2015.org

Abstract

Over-Head Lines’ (OHL) cables operate in severe conditions, subjected to many environmental and operation factors such as wind, moisture, voltage stress, current and temperature excursions and also to structural imperfections. Furthermore, during a lifetime spanning decades, repairs, refurbishments and modifications lead to cable cuts, amendments and re-stressing. Utilities have been searching for a method
to autonomously perform inspections of OHL without de-energizing the cables and featuring as many functions as possible to improve the condition estimate. Periodic inspections are carried out mainly using
helicopters or experienced teams from the ground, and this usually takes a lot of time and effort due to lack of accessibility. However there are some critical conditions, such as inner corrosion, that must be
inspected from close range to the cables that are beyond the reach of a helicopter or a drone. A solution is proposed in the form of Long Range Ultrasonic Testing (LRUT) as a Non-Destructive Testing (NDT)
technique. The LRUT can be used to identify the presence and the location of defects inside the cable.
The prototype developed by the CHAPLIN, a R&D project consortium funded by the European Commission under the 7th Framework Programme (FP7), can detect defects until 50 meters from the
transducer position on the cable. Since the medium span length on transmission lines ranges from 300 to 500 meters, it will be desirable to improve detection to inspect most of the spans from one or two positions
only. The prototype should attach automatically to the cable and for future operation it could be placed using a UAV for instance. The wireless communications and energy harvest module are presented as
ancillary technologies to leverage the operation of this prototype. Considerations on how to bring the prototype to the operation level as well as needs perceived by utilities are discussed as they should drive
further developments.

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