Risk Based Maintenance and Lifetime Management of Overhead Lines

The Portuguese transmission system operator launched a long term enterprise for developing a risk based methodology to optimise Overhead Line lifetime and maintenance costs, based on asset information, inspection, maintenance and third party data. The methodology must provide next-day and next-year risk estimates for operation and maintenance, respectively. The authors propose combining heterogeneous information into a probabilistic model that may be used to find maintenance policies optimizing the trade-off between cost reduction and higher quality of service. It leverages field data from helicopter inspections, dispatch event records and third party data. Such approach is most suitable for Overhead Lines’s risk analysis and estimation, since Overhead Lines spread across heterogeneous territories and are subject to diverse environmental factors. The procedure considers the interaction between each Overhead Line and its space-time context, thus departing from the more traditional single component view towards a system analysis. To cope with the heterogeneity covered by transmission Overhead Lines, the model’s spatial resolution is data driven according to how data is geographically framed, while the time unit may range from seconds to years, thus satisfying the diverse time-scope requirements of the undergoing work promoted by REN, the Portuguese transmission system operator. The methodology is generic enough to be applied to different contingencies. The paper presents the risk based approach pursued by the Portuguese transmission system operator to reduce maintenance cost while increase equipment availability, and shows an example of application considering the reliability of eighteen Overhead Lines due to wild fires, fog, and obstacles collisions, like trees.