Inspection of energized aged conductors using non-destructive, in-situ inspection technology

Abstract

Many overhead transmission lines (OHTL) around the world are very old. Some overhead conductors and ground wires have been in-service since the 1920’s, well past their intended design life, and with deterioration rates largely unknown. As lines continue to age, it becomes increasingly important for utilities to know the existing physical condition of aged conductors and ground wires for safety and reliability reasons but also to optimize the timely expenditures of maintenance and capital budgets. Conductors are of primary interest because their condition often drives asset management decisions.Live-line working is of highest importance for most maintenance operations, and the need to maintain system availability is a significant factor in the introduction of robotics in this field. In order to maintain or increase the reliability of OHTLs, new maintenance techniques are becoming available to assess and diagnose the condition of various OHTL components. Line inspection and maintenance of OHLs already benefit from developments in mobile robotics, which can reduce the potential risk to maintenance crews (e.g. live working), inspection of wire, reach hardly accessible spans (e.g. river crossings), perform tedious work faster, and finally decrease costs. Line inspection robot is a field-based, non-destructive inspection system that “looks through” the aluminium wires and into the steel core wires. Its function is to measure the remaining cross-sectional area of steel wires and to detect any localized breaks or corrosion pits. In many cases. The inspections have to be performed on energized conductors in order to avoid costly power outage. A study into the degradation process of conductors in various environments was undertaken to better understand the various stages of corrosion over time. This information is useful when used with the non-destructive in-situ testing and the asset management model to determine timeframes for projects such as the maintenance or replacement of the conductors.