The Effects of System Design on Reliability and Risk

A majority a states now require electric utilities to provide annual reports on distribution system reliability. An increasing number are setting performance targets that utilities are expected to meet. For these reasons, most utilities are placing an increased emphasis on reliability improvement. Efforts typically begin with "low hanging fruit" such as proper vegetation management, animal guards, and replacement of deteriorated equipment. After this is done, utilities must begin to look at the effect of system design on reliability. Utilities are not just interested in expected reliability performance. Rather, they are interested in managing the probability that performance targets will be met. This paper examines distribution system design in this context. It begins by providing an overview of asset management and system design. The paper concludes by analyzing the inherent reliability and risk associated with different types of feeder designs including the use of manual switching, automated switching, reclosers, and looped topologies