MAXIMIZING RELIABILITY AND MINIMIZING COST IN URBAN CENTRAL BUSINESS DISTRICTS USING A PROBABILISTIC DESIGN PROCESS

摘要

The practices employed by many utilities in designing urban distribution systems evolved during the 1920's. In those "good old days," distribution systems were not being pushed to the extent that they are today, assets were not as aged as they now are, thermal and spatial constraints were less severe, customer expectations were less demanding, and utilities were not faced with the regulatory and competitive pressures that exist in today's market. In addition, labor costs were dramatically lower, with the result that operating expenditures were less of a factor so that design decisions could be based mainly on capital costs. Today, the rules of the game are fluid and the challenges facing distribution utilities are unprecedented. In this dynamic environment, utility managers are starting to search for new approaches to design. Their objectives in this search are to identify approaches and technologies that enable them to deliver an acceptable level of end-customer reliability and satisfaction, at reasonable capital and operating costs, while managing the political and public relations risks that are an inevitable factor in regulated utility businesses. This paper will present the case for a new design process in a modern distribution utility based on probabilistic principles. A common practice in the past to ensure reliability and simplify engineering was to design to a deterministic standard such as N-1 or N-2 redundancy, regardless of the application or environment. The paper will examine the impact of deterministic standards on the evolution of the system, and highlight the potential deficiencies of this design process in a constrained and changing environment. The probabilistic design process will be explained and illustrated on an example sub-system and the cost, reliability and risk implications will be discussed.