A.RI.EL: A structural integrity condition based method for renewal assessment of pylons in overhead transmission lines

The structural integrity and performance of pylons in overhead high voltage transmission lines is essential to maintain the reliability of supplying customers and ensuring public safety. Condition assessment program of the Terna transmission lines asset is based on different types of periodic, systematic (inspectional and technical) and non-systematic (occasional) controls and have the main function of maintaining a continuous global understanding of the power lines and surrounding territory status. The control program monitors and records the condition of all the structures and components of transmission lines and of the lattice steel pylons in particular. Surveillance and inspection control results - generally carried out by means of visual inspection from the ground, visual or instrumental inspection from helicopter with LIDAR, IR and UV camera - are collected and automatically analyzed by a dedicated algorithm in a proprietary data base (MBI-Lines). When the analysis output from MBI Data Base is a proposal of a renewal for a pylons of a line, the validation is carried out by means of ARIEL (Power Line Renewal Analysis), the new developed experimental-theoretical approach which provides some objective parameters correlated to the actual, current structural condition of the pylons. On a properly selected set of pylons of the transmission line under investigation, in-field and laboratory tests are carried out in addition to numerical simulation of the structural behavior of pylons in the actual operating and environmental conditions. Analysis results are then properly extended to all the pylons of the line. If replacement is not confirmed, the forecast of the residual life in safe operating conditions for all the pylons of a line is provided, supporting the asset management decision making process. This paper shows the fundamental criteria underlying the ARIEL approach.