VALUE-BASED ELECTRIC DISTRIBUTION SYSTEMS RELIABILITY ASSESSMENT
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In order to make a consistent appraisal of reliability and economics in the planning of electric power systems, there is a growing interest in an economic optimization approaches which relate the costs and benefits associated with various levels of system reliability. This thesis describes a value-based approach for the assessment of distribution system reliability. The worth of system reliability is assessed by relating it to the costs or losses incurred by utility customers as a result of power failures. Customer interruption costs were obtained from a recent NSERC sponsored survey of customers of seven Canadian utility service areas conducted by the Power Systems Research Group at the University of Saskatchewan. The value-based analyses described in this thesis is illustrated by application to the distribution segment of a hypothetical reliability test system. The analyses involve the evaluation of the reliability of the subtransmission and radial distribution segments of the test system and the corresponding reliability worth at the customer level. The reliability of a given system configuration is evaluated in terms of the load point indices, the system performance indices and the expected customer outage costs. In the subtransmission system reliability assessment, the evaluated indices and the expected customer outage costs for a given system configuration are used to assess the impact of the different types of failure modes encountered in subtransmission systems. The analysis identifies the subtransmission components and parameters which make a significant contribution to customer supply inadequacy and outage costs. A value-based approach is presented for assessing the optimal level of customer service reliability based on calculating the costs associated with various system configurations and evaluating the corresponding worth or benefits at the customer level. An approach for the optimum location of protective and switching devices in distribution circuits is also developed in which the decision to install a device at a location is based on maximizing the savings in the customer outage costs. Appropriate sensitivity studies are conducted to illustrate how the worth of system reliability is affected by design/operational factors. The studies and procedures described in this thesis can assist power system planners to establish target system reliability levels and to justify additional distribution system facilities required to provide acceptable system performance.