The traditional N - 1 security criterion provides only a limited perspective on the actual level of security of a power system and a risk-based approach to security assessment provides considerably more information on which to base operating decisions. It further argues that this risk should be measured in terms of expected outage costs to the consumers. Furthermore, the risk calculation should not be limited to the consideration of a predefined set of contingencies but should factor in the actual probabilities of outages leading to load disconnections. A case study based on the IEEE-Reliability Test System shows that different operating points on the system's deterministic security boundary have very different levels of risk. For a given operating point, the risk level changes considerably between fair, average and bad weather conditions. Finally, the paper shows how, using adaptive deterministic security boundaries, it is possible to compare the cost and benefit of relaxing operating limits.

Comparison of risk-based and deterministic security assessments

This paper gives a detailed account of the current practices used in Brazil for probabilistic reliability assessment of the national power grid, from the adequacy point of view. These procedures are utilized by the Brazilian independent electric system operator and were recently made mandatory by the National Electric Energy Regulatory Agency (ANEEL).

Power System Probabilistic Reliability Assessment: Current Procedures in Brazil

Tracing the unreliability and recognizing the major unreliability contribution of network components

A multi-dimensional analysis of reliability criteria: From deterministic N − 1 to a probabilistic approach

A machine-learning based probabilistic perspective on dynamic security assessment

This paper describes a practical method of probabilistic reliability assessment (PRA) for large interconnected power systems. It takes a large number of contingency load flow simulations and combine them with a practical method of characterizing the effect of the availabilities of generators, lines and transformers for computing meaningful probabilistic reliability indices (PRI). The method was demonstrated on the US Eastern interconnection and has been applied by several utilities belonging to the EPRI PRA user group. The ability of the method to provide insights on root causes, weak points and regional causes and effects was shown. Results would also be useful for developing effective remedial actions or investment options. The reliability indices could be used for measuring or monitoring bottlenecks, if an online computation of these indices is implemented. They can also be used as one of several performance indices for transmission investment decisions.

S.T. Lee

Papers

A practical probabilistic reliability assessment using contingency simulation