Modeling failure data of overhead distribution systems

An overhead power line can be regarded as a collection of components each of which contribute in a particular way to its reliability. An overhead distribution system is a collection of such lines. A repairable system is a system which after failing, can be restored to an operational, but not a new state by repairing or replacing one or more components. This work treats the distribution system as a holistic entity with the aim of measuring the pattern of failures as an indication of reliability growth or deterioration. Comparison is made using case studies of an urban and a rural system based on trend analysis, the Laplace statistic and confidence limits. It is argued that although the pattern of failure of a distribution system may emulate a stationary point process, this can be misleading in the assessment of reliability and the impact of maintenance policies.