Failure analysis of in service failed resin cable joints by means of a statistical approach

Statistical failure analysis can be a powerful tool for asset replacement strategies. In parts of the Netherlands, a specific type of resin joint for 10 kV paper-oil insulated cables was applied substantially in the 1970's. These joints have now a considerable contribution in outage time because of breakdown of the resin insulation. The reported failures over the last six years, together with the population still in service are used as input for statistical analysis with Weibull and Normal distributions. It can be concluded that the joints are in their wear-out life period and that ageing is the main reason for failures. The total number of expected failures, obtained from the analysis, shows an increasing trend in coming years. A testing program, started a few years ago, influences the failure behavior. An active replacement strategy can also influence the number of expected failures. A comparison is made between the influence of testing and replacement strategy.