An improved method for hourly reliability ranking of distribution network zones

In recent years by increasing the sensitivity of loads to electricity power quality as well as power industry liberalization and reconstruction, distribution system reliability evaluation has been become more important. On the other hand with technology progression, time-varying tariffs of consumption electricity and increasing the diversity of loads in distribution network, inattention to the issue of load variation and its effects on distribution system reliability at different times and zonal conditions, does not have any justification. Considering load variation effects on reliability indices of the different zones of a distribution network, this paper applies a method for calculation of the expected interruption duration to rank the zones at each hour of a typical day that can be used in distribution network management, operation and expansion planning. With the aim of this method, taking into account the costumers' class, the loads are modeled and by means of a concept so called "Reliability Zones" in power systems, zonal reliability of the distribution network is assessed hourly along a day and the reliability zones are ranked based on their expected interruption duration.