Quantitative assessment of the effect of overhead and underground feeder configurations on the reliability of urban mixed distribution systems

• Impact of the ratio and location of overhead and underground feeder sections on the mixed distribution systems (MDS) reliability is evaluated. • Impact of various MDS on the customer-wise, feeder-wise, and system reliability indices is evaluated. • Reliability of various MDS are compared with those using traditional all-overhead (AO) and all-underground (AU) systems. • Impact of failure rates and repair times on EENS and ECOST due to various feeder configurations is assessed. Mixed distribution systems (MDS) aim to balance between the failure frequency and restoration time of all-overhead (AO) and all-underground (AU) distribution systems. The reliability indices of MDS are influenced by the feeder configurations of overhead lines (OHL) and underground cables (UGC), connected customer types along with the failure rates and repair times associated with OHL and UGC. This study investigates how variations in the location, ratio, failure rates and repair times of overhead and underground feeder sections within mixed feeders affect the reliability of MDS in urban environments. The reliability indices of MDS are compared with those that use AO and AU networks. In addition to looking at how the ratio and location of OHL and UGC affect reliability, four cases are analyzed to assess the effect of the variation of OHL and UGC failure rates and repair times on reliability indices for different MDS feeder configurations. Results indicate that MDS could effectively balance the reliability of the AO and AU systems, providing useful information for power system designers and policymakers for efficient utility planning and infrastructure development. Furthermore, the cost-benefit impact of OHL and UGC failure rates and repair times may differ significantly depending on the MDS feeder configurations.