System reliability estimation and component replacement analysis for electricity transmission and distribution systems

This PhD dissertation focuses on the development of mathematical methods that can be readily applied to obtain the reliability of Electricity Transmission and Distribution Systems (ETDS) and to determine long-term component replacement strategies for aging ETDS components. This work has devoted research efforts to develop electric power reliability models that can be used to accurately approximate the system outage rate, average repair time, and expected system downtime of ETDS configurations used by the power industry for different types of outages. Additionally, new component criticality importance measures have been developed. Several existing popular reliability criticality importance measures (e.g., Birnbaum, Reliability Achievement Worth) cannot be directly applied to these power systems, because they have been developed mainly for components with specified finite mission times. Alternatively, for ETDS, the different components within the system exhibit outage rates and repair rates instead of probability of failure for a specified time interval. Most of the U.S. power grid was built in the early 1960s. ETDS are often built with redundancy to minimize the number and duration of interruptions. They have been operating reliably in the past, but as equipment ages, it fails more frequently and it becomes economically important to plan the expensive replacements and/or restorations of aging equipment. Determining the planned retirement of aged equipment in the ETDS is an important research area, because the aged equipment is continuously used until it fails. It can take more than one year to complete the whole replacement process of some critical components. The component replacement analysis method proposed is based on an integrated iterative dynamic programming and integer programming approach. This method works under the consideration of heterogeneous assets with different ages subject to annually budget constraints. The method developed can be applied to systems composed with sets of heterogeneous assets. This is a new solution methodology that offers distinct benefits to previous methods, which only pertained directly to a system composed of homogeneous assets. This research leads to many research contributions specific to ETDS. However, the replacement analysis model represents a novel approach that can be applied to many types of systems and problems.Ph.D.Includes bibliographical references (p. 181-186)