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Performance evaluation of a combined generation and transmission system normally includes the independent outages of generators, transformers and transmission lines. However, substation originated outages due to failure of breakers, transformers and busbars can also have a significant effect on the bulk power system performance indices in terms of outage frequency and duration. The studies described in this paper utilized various substation components such as breakers, busbars and transformers to develop a general-purpose software to assess the reliability of the system. It performs failure modes and effect analysis and provides a concise and orderly description of the various combinations of occurrences within a system that could result in an interruption of supply. Reliability analysis technique using the minimal cut set method has been implemented. In addition the software package is able to define and incorporate 15 types of system configurations in the analysis and at the same time, comprehensive analysis tools such as print, save, sensitivity studies, tutorial guide, etc., are also included. The concept associated with the reliability analysis is illustrated by application to a simple but comprehensive system configuration. Keywords: Substation reliability; Software development; Reliability analysis

This paper presents a system well-being evaluation method that divides the composite power system operating condition into several states depending on the level to which the adequacy and security constraints are satisfied. Conventional composite system reliability indices typically do not reflect the ability of the system to withstand, without resulting in load curtailment or other violations, the abrupt loss of system components. The well-being evaluation method provides an extra index for system planners or designers to decide whether or not the power system is capable, based on the deterministic criteria, to withstand unplanned outages of system components without violation of specified constraints. The well-being indices, which are the probabilities of the system being in the healthy, marginal and at risk states, provide this important and intuitively interpretable information for system planning and operations. Studies on two test systems were done to examine the effect of load levels, system component removal and addition on the well-being indices. The bus well-being indices for selected buses of the two test systems were also calculated and compared with the system well-being indices. Keywords: Composite systems; Well-being analysis; Adequacy assessment; Health analysis; Deterministic criteria

The basic concepts associated with quantitative reliability assessment of electric power systems are reasonably well established and well accepted by the power industry. The evaluation of the costs and benefits of competing investments is now becoming a standard practice in power system planning. The justification of new facilities and system modifications now normally includes specific reference to reliability and one approach that is receiving 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. In order to make a consistent appraisal of economics and reliability, it is imperative to compare the 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. This paper discusses the developments made in existing techniques in the area of power system reliability cost/benefit evaluation and application. Reliability worth data presently used in cost/worth evaluation are presented, and their applications in conjunction with the system reliability indices are also presented in this paper. Keywords: Reliability cost; Reliability worth; Customer survey; Outrage costs; Value-based reliability; Power system reliability; Worth of supply; Supply reliability

When a utility buys electric energy from a non-utility generation (NUG) at short notice, such as a few hours, one of the most difficult issues encountered by the utility is the evaluation of the rate (buyback rate) it should pay the NUG such that the utility maximizes its economic benefits. Utilities calculate their purchase rates based on a number of different formulae. Short term buyback rates should be based on the operating cost that a utility avoids by utilizing energy from a NUG. This cost is termed as the avoided operating cost (AOC) in this paper. This paper illustrates a technique, which can be utilized to evaluate the AOC under different operating conditions in a just and reasonable fashion and that can be verified by both the utility and the NUG. Significant aspects of NUG are examined and discussed in this paper using a small test system. Sensitivity studies, similar to those illustrated in this paper, can be utilized to estimate the savings in the running cost incurred by a utility when it buys electrical energy from NUG. [C] 2001 Elsevier Science Ltd. All rights reserved. Keywords: Avoided operating cost; Non-utility generation; Composite system; Generation and transmission planning; Operating reserve

Supply reliability of sub-transmission systems is usually quantified in terms of two sets of indices, the individual supply/load point indices (average failure rate, average outage duration and average annual unavailability) and the system performance indices (SAIFI, SAIDI, CAIDI, ASUI, ASAI, etc.). These probabilistic indices are very useful not only for assessing the severity of system failures in future reliability predictions but also in assessing the system's past performance. Many utilities, however, continue to use deterministic methods (rule-of-thumb methods) to assess the reliability of their systems. This paper presents a method designated as system well-being analysis, which in addition to the conventional probabilistic risk index of supply point unavailability, also incorporates the specified deterministic criteria in defining additional system healthy and marginal states. The proposed method is illustrated in this paper by calculating the well-being indices of a small but comprehensive test electric sub-transmission system to show the effects of some pertinent factors and deterministic criteria on the system well-being indices. [C] 2000 Elsevier Science Ltd. All rights reserved. Keywords: Well-being framework; Sub-transmission system; Deterministic criteria; System health; Probabilistic analysis

Substations and switching stations (herein referred to only as stations) are the pivotal parts of power systems. Failure events in stations often result in multiple outages of generators, lines, and bulk load points in a composite system, which may have serious impact on the security and stability of power systems. This paper presents the application of a Monte Carlo simulation method to the reliability evaluation of stations in transmission systems. The comprehensive impacts of station-originated failure events on composite systems are investigated using the developed technique. The proposed approach is illustrated by application to a test system. The effect of breaker failure rate in station on system reliability indices is also assessed in the paper. The paper provides valuable information for decision-making in power system planning and operation. [C] 2000 Elsevier Science Ltd. All rights reserved. Keywords: Monte Carlo simulation; Reliability evaluation; Station-originated outages; Sensitivity study