Extending health considerations in subtransmission systems to include reliability worth

Abstract

The basic concepts associated with quantitative reliability assessment of electric power systems are reasonably well established, and well accepted within the power industry. The evaluation of the costs and benefits of competing investments is now becoming a standard practice in power-system planning. To justify the use of new facilities and system modification specific reference to reliability has normally been included, and one approach that has received considerable attention is the evaluation of the societal worth (benefit) of system reliability, or conversely the costs incurred by consumers due to power supply interruptions. To make a consistent appraisal of economics and reliability, it is necessary to compare investment cost needed to attain a specified level of reliability with the reliability worth or benefits derived by the society at that level of system reliability. The well-being framework is extended to include the societal worth of electric service reliability in subtransmission systems. System well-being is defined in terms of three system states: (i) healthy, (ii) marginal and (iii) at risk, thus combining the deterministic and probabilistic approaches into a single framework. The determination of reliability worth indices of expected energy not supplied (EENS), expected cost of interruptions (ECOST) and interrupted energy assessment rate (IEAR) are discussed, for both the healthy and at risk states in the well-being framework. The concepts associated with extending the well-being framework to include reliability worth parameters are illustrated by application to a small reliability test system designated RBTS.