Approximate methods for event-based customer interruption cost evaluation

There is increasing interest in the new deregulated electric utility environment in assessing the customer costs associated with failures in electric power supply and the responsibilities associated with these failures. The customer interruption cost when an electric supply failure occurs depends on many factors, such as the customer types interrupted, the actual load demand at the time of the outage, the duration of the outage, the time of day and the day in which the outage occurs. The absence of many of the data sets required in a detailed evaluation of the customer costs makes it difficult to estimate precise individual customer outage costs due to a specific failure event. This paper illustrates the development of approximate methods for event-based customer interruption cost evaluation on a distribution feeder subjected to a specific outage event. A series of approximate methods are presented and the outage cost estimates are compared with a set of base method results. The approximate methods are based on the use of customer sector data sets, i.e., commercial, industrial, residential data, which are generally available to most utilities. The paper also illustrates further simplifications of the approximate techniques which reduce the effort required to estimate the outage costs. The approximate techniques provide a practical approach to evaluating a specific outage event.