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Failure data together with the length and the ages of mass-insulated power cables the still in service of a Dutch utility are used as input for the statistical analysis. The choice of the appropriate distribution depends on the goodness of fit to the data. The fitted statistical distribution gives the relation of the number of expected failures per kilometer together with the age of the cable. To...
One of the tools to answer some typical asset management (AM) questions is the use of statistical analysis of life time data of high voltage components. When life time data of components is available, statistical analysis can be performed. The analysis can give information about the failure rate of components, expected failures in the future, conditional remaining life estimation and influence of...
The VHF/UHF PD detection technique is a nonintrusive method for power cable PD diagnostics. It incorporates a VHF/UHF current probe placed at the grounding of the cable and a measuring device (e.g. spectrum analyzer or tunable filter) connected to the probe. This way it is possible to obtain phase resolved patterns with very high signal to noise ratio.
The practical interest of power utilities regarding the maintenance and replacement policy of insulating systems such as cables, switchgear and transformers is often based on experiences knowledge and data from the past. The ages of components in the network are increasing and this can result in an increase of the number of failures in coming years. To be able to monitor the components powerful tools...
The failure behavior of resin cable joints in the medium voltage underground network in the Netherlands shows a correlation with the ambient temperature of the air above the ground. This behavior is especially seen when the failures occurred during the summer months are considered. In the last years the months July or August were very hot and the number of failures increased significantly in these...
In this paper the results of after-laying testing of transmission power cable accessories using a non-conventional technique are being presented. The non-conventional system is based on the detection of high frequency signals being emitted by the partial discharge. Therefore, each power cable accessory is equipped with either an internal or external sensor to decouple the partial discharge signals...
In the 1960's up to the 1980's a very compact oil-filled switchgear assembly was installed in the 50 kV networks of different utilities in the Netherlands. Per bay the switchgear consists of different oil-filled compartments where the high voltage parts are supported and connected from one compartment to the other by epoxy resin bushings. The population of this type of bushing is relative large. The...
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...
In this article, the theoretical considerations that have to be taken into account when using statistical failure analyses of service-aged components are discussed. Furthermore, two case studies in which statistical failure analysis is used to predict future failures and to see in what way strategies can influence this prediction are included. Then, conclusions are drawn based on the analysis of the...
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