This thesis describes a study of the probabilistic elements of failure and hazard as they impact upon the processes of engineering decision making when applied to a widespread, overhead electricity distribution system. It is concerned not with the development of new theoretical concepts in the field of risk analysis but with the application of known statistical techniques to the largely neglected area of risk analysis as it is applied to such systems. The basic objective is that of the development of a unified, systematic ^proach to uncertainty in decision making as it affects design, maintenance and replacement policies which, often as not, are made under conditions involving the allocation of scarce resources - funds, manpower, time and materials. Implicit in this view is the notion that the operation of a system is conditioned by its working environment. Therefore, vjhat appears the best way to manage one particular system may be neither obvious or necessarily applicable to another. In this respect, it is considered that the distinct contribution made by the work in the area of risk engineering a power distribution system is that it provides a comparatively simple, disciplined methodology for the analysis and rationalisation of failure data and hazard collection phenomena.
The author's experience in the field of transmission and distribution system engineering and management, spanning some thirty years, is that decision making as it applies to preventive maintenance and replacement policies is an area where subjective beliefs have generally taken precedence over systematic, objective analysis. The reasons reside in the interrelated problems posed by:
1. The lack of an appropriate statistical technique which can be used to model the problems of risk peculiar to a distribution system.
2. Access to reliable, quantitive system and component failure information from which to calculate risk parameters and to relate them to hazard or catastrophe situations.
3. The probabilistic difficulties of placing into fiscal context the outcome of litigation as it relates to the insurability and service continuity of a distribution system. ............................................