Evaluation of reliability worth

As discussed in Chapter 1, the basic function of an electric power system is to satisfy the system load and energy requirements as economically as possible and with a reasonable assurance of continuity and quality [1]. The two aspects of relatively low cost electrical energy at a high level of reliability are often in direct conflict and present power system managers, planners, and operators with a wide range of challenging problems. Electric power utilities are also facing increasing uncertainty regarding the economic, political, societal, and environmental constraints under which they operate and plan their future systems. This has created increasing requirements for extensive justification of new facilities and increased emphasis on the optimization of system costs and reliability. An integral element in the overall problem of allocating capital and operating resources is the assessment of reliability cost and reliability worth [2]. The ability to assess the costs associated with providing reliable service is reasonably well established and accepted [3, 4]. In contrast, the ability to assess the worth of providing reliable service is not well established and considerable work will be required before these methodologies can be considered to be completely acceptable. Establishing the worth of service reliability is a difficult and subjective task, as direct evaluation does not appear to be feasible at this time. A practical alternative, which is being widely utilized, is to evaluate the impacts and the monetary losses incurred by customers due to electric power supply failures.