Billinton, Roy2017-08-162017-08-161997-12December 1http://hdl.handle.net/10388/8022Increasing interest in economic optimization approaches in power system planning and expansion have resulted in a higher awareness in reliability worth of electricity supply. The interruption costs incurred by customers due to power supply failures is an important parameter in assessing the worth or benefit associated with a particular level of reliability. Future interruption costs associated with system development of expansion can be predicted using an appropriate customer damage function in association with customer reliability indices. It is also possible to develop an Interrupted Energy Assessment Rate (IEAR) which links the customer interruption costs and the adequacy indices normally used for planning and operating purposes. ) This thesis is concerned with the sensitivity of the lEAR at hierarchical level I (HLI), hierarchical level Il (HLII) and in the distribution functional zone. Assessment of reliability worth is an extension of quantitative reliability evaluation. The evaluation of an lEAR involves a frequency and duration approach in association with customer damage functions. Sets of lEAR values have been calculated considering the impact of various factors at HLI, Hill and in the distribution functional zone. The lEAR sensitivity studies show that the lEAR is reasonably stable under different operating conditions, which greatly simplifies the predictive reliability worth assessment process. This thesis also examines the economic optimum service reliability levels at HLI and HLII using a small test system, and shows how this level is affected by unit capacity, peak load and customer damage functions.Thesis