Network reliability analysis is usually based on minimal path or cut enumeration from which the associated reliability expressions are deduced. The cut-set method is a popular approach in the reliability analysis of many systems from simple to complex configurations. The computational requirements necessary to determine the minimal cut-sets of a network depend mainly on the number of minimal paths between the source and the sink. A technique designated as the "Path Tracing Algorithm" is presented in this paper, which can handle both simple and complex networks, and considers both unidirectional and bi-directional branches. A step by step procedure is explained using a bridge-network. The algorithm is easy to program, and does not require limits on the size of the network. The applicability of the proposed technique is illustrated by application to a more complicated system.

Reliability is an important issue in power systems and historically has been assessed using deterministic criteria and indexes. However, these approaches can be, and in many cases have been, replaced by probabilistic methods that are able to respond to the actual stochastic factors that influence the reliability of the system. In the days of global, completely integrated and/or nationalized electricity supply industries, the only significant objective was the reliability seen by actual end users. Also, the system was structured in a relatively simple way such that generation, transmission, and distribution could be assessed as a series of sequential hierarchical levels. Failures at any level could cause interruptions of supply to the end user. All planning and operational criteria were intended to minimize such interruptions within economic limits. The system has been, or is being, restructured and now many individual parties are involved, often competitively, including generators, network owners, network operators, energy suppliers, regulators, as well as the end users. Each of these parties has a need to know the quality and performance of the system sector or subsector for which they are responsible. Therefore, there is now a need for a range of reliability measures; the actual measure(s) needed varying between the different system parties. This paper addresses these issues and, in particular, reviews existing approaches and how these may be used and/or adapted to suit the needs and the required indexes of the new competitive industry and the different parties associated with it.

An approach often used to estimate power-system reliability worth is to determine consumers' monetary losses resulting from service interruptions, i.e. the cost of unreliability. Previously, studies have been conducted to provide estimates of customer interruption costs, and a wide range of methodologies has evolved. There is no universal agreement on the appropriateness of methodologies to particular situations nor on the interpretation of the results obtained, but some appear to be more acceptable and useful to the industry than others. A survey is presented of the techniques available for estimating customer interruption costs, the rationale of those that are currently popular is discussed, and the application of such cost data in creating a composite customer damage function is explored.>