Reliability aspects concerning distribution system expansion planning

The authors present state of the art concerning reliability analysis in Norwegian distribution systems. Reliability analysis is used both for minor investigations concerning new control equipment, location of breakers, etc. as well as in distribution system expansion planning. Studies performed show that even with a conservative estimate of the specific cost of nondelivered energy, outage costs dominate total distribution costs in radial overhead systems. Hence the central energy authorities have to ensure that relevant requirements regarding reliability are applied by the utilities in system planning. Uncertainties concerning outage costs should not prevent utilities from including the reliability aspect in system planning. Sensitivity analysis is easy to perform using available planning tools. Adequate location of circuit breakers has a large impact on nondelivered energy, in particular when disconnectors are remote controlled. Mobile generating units have only small effects on total outage indices, but may improve significantly outage conditions for preferenced loads