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Power distribution systems should meet demands such as high reliability, efficiency, and penetration of renewable energy generators (REGs) in a smart grid. In general, power distribution systems are radial in nature. One-way power flow is the advantage of a radial system. However, the introduction of REGs causes bidirectional power flow. Furthermore, there are limits to improvements in reliability and efficiency in a radial system. Therefore, the upgrading of primary feeders from a radial to a loop configuration has been considered in the Korea Smart Distribution Project. An advanced power distribution system (APDS), in which primary feeders operate in a loop configuration, has been explored in this paper. First, the design scheme of a conventional power distribution system configuration that adopts distribution automation is introduced. Subsequently, an upgrading scheme of loop configuration using normally opened tie switches and a tie switch selection algorithm for loss minimization are described. Finally, the advantages of the upgraded configuration are reported through case studies. It is observed that the APDS configuration can integrate more REGs from the viewpoint of voltage regulation. An advanced distribution system allowing greater use of REGs will be a major contribution to smart grid implementation.