This oeportdescribesan enhanced testsystem ( W W ) f o r MW In bulk power system reliability evaluation studies. The value of the tost system is that it will permit comparative and benchmark studios to be perf0me-d on new and existing reliability evaluation techniques. The test system was developed by modifying and updating the original IEEE RTS (referred to as RTS79 hereafter) to reflect changes In evaluation methodologies and to overcome perceived deficiencies. -The first version of the IEEE Reliability Test System (RTS 79) was developed and published in 1979 [ l ] by the Application of Probability Methods (APM) Subcommittee of the Power System Englaeering Committee. It was developed to satisfy the need for a standardized data base to test and compare results from different power system reliability evaluation methodologies. As such, was designed to b@ a reference system that contains the core data and system parameters necessary for composite reliability evaluation methods. It was recognized at that time that enhancements to RTS It should be noted that In developing and adopting the various parameters for RTS-96, there was no Intention to develop a test system which was representative of any specific or typical power system. Forcing such a requirement on RTs-98 would result in a

Control room operators are faced with frequent security-economy decision-making situations necessitated by stressed system operating conditions, and there is increased need for securityeconomy decision-support tools. Although probabilistic methods are promising in this regard, they have been mainly used in planning environments. This task force paper explores their use for operational decision-making, comparing them to the more traditional deterministic approach. Two examples are used to facilitate this comparison via overload and low voltage security assessment to identify secure regions of operation for a small 5-bus system and for the IEEE Reliability Test System. The results of this comparison show that the probabilistic approach offers several inherent advantages.

Abstract-In this paper, the most frequently used maintenance strategies are reviewed. Distinction is made between strategies where maintenance consists of replacement by a new (or "good as new") component and where it is represented by a less costly activity resulting in a limited improvement of the component's condition. Methods are also divided into categories where maintenance is performed at fixed intervals and where it is carried out as needed. A further distinction is made between heuristic methods and those based on mathematical models; the models themselves can be deterministic or probabilistic.From a review of present maintenance policies in electric utilities it is concluded that maintenance at fixed intervals is the most frequently used approach, often augmented by additional corrections. Newer "as needed"-type methods, such as reliability-centered maintenance (RCM), are increasingly considered for application in North America, but methods based on mathematical models are hardly ever used or even considered. Yet only mathematical approaches where component deterioration and condition improvement by maintenance are quantitatively linked can determine the effect of maintenance on reliability. Although more complex, probabilistic models have advantages over deterministic ones: they are capable of describing actual processes more realistically, and also facilitate optimization for maximal reliability or minimal costs.

Abstract-In this paper, the most frequently used maintenance strategies are reviewed. Distinction is made between strategies where maintenance consists of replacement by a new (or "good as new") component and where it is represented by a less costly activity resulting in a limited improvement of the component's condition. Methods are also divided into categories where maintenance is performed at fixed intervals and where it is carried out as needed. A further distinction is made between heuristic methods and those based on mathematical models; the models themselves can be deterministic or probabilistic.From a review of present maintenance policies in electric utilities it is concluded that maintenance at fixed intervals is the most frequently used approach, often augmented by additional corrections. Newer "as needed"-type methods, such as reliability-centered maintenance (RCM), are increasingly considered for application in North America, but methods based on mathematical models are hardly ever used or even considered. Yet only mathematical approaches where component deterioration and condition improvement by maintenance are quantitatively linked can determine the effect of maintenance on reliability. Although more complex, probabilistic models have advantages over deterministic ones: they are capable of describing actual processes more realistically, and also facilitate optimization for maximal reliability or minimal costs.

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