Enhancing reliability for medium voltage underground power lines

In order to develop effective methods for reliability centred maintenance and to model operational reliability for transmission and distribution power systems, different reliability growth tools are implemented. The purpose of such reliability growth models is to identify all the multiple situations when changes on reliability for a given system appear, and to determine some specific indices. Crow-AMSAA model is used frequently within analyses related to enhancing reliability for different systems. The paper presents a research developed on 6 underground power lines (UPL) of a 20 kV substation, based on incidents recorded during the UPL exploitation. For analyses, the Reliability Growth Plots v.7 (RGA) module, produced by ReliaSoft Corporation has been used. All data obtained after RGA application, are related to reliability indices determination and to reliability growth plots modeling: Cumulative Numbers of Failures vs. Time, MTBF, Failure Intensity vs. Time. The results were compared with those existing in the scientific literature. The reliability growth index prognosis for all UPL that now are in service represents the final result of the research. These predicted indices are useful for modelling reliability centred maintenance.