Distribution systems — extended techniques

The models and techniques described in Chapter 8 allow the three basic reliability indices, expected failure rate (λ), average outage duration (r) and average annual outage time (U), to be evaluated for each load point of any meshed or parallel system. These three basic indices permit a measure of reliability at each load point to be quantified and allow subsidiary indices such as the customer interruption indices (see Section 7.3.2) to be found. They have three major deficiencies, however: (a)they cannot differentiate between the interruption of large and small loads;(b)they do not recognize the effects of load growth by existing customers or additional new loads;(c)they cannot be used to compare the cost—benefit ratios of alternative reinforcement schemes nor to indicate the most suitable timing of such reinforcements.