Abstract
The authors present a novel automatic transient stability classification approach, based on a two-stage hierarchical classifier obtained through the combination of two different pattern recognition structures. The first-level classifier uses low-cost computational variables evaluated at the fault occurrence moment. The classification structure used in this first level is a linear one and is obtained through the combination of a Fisher discriminant transformation and a Bayesian probabilistic approach for the independent term determination. The second-level classifier uses a new set of transient variables, directly related to kinetic and potential energies at the fault clearance moment. The classification structure in this second level is based on a weighted K nearest-neighbor rule, using a Euclidian metric defined in an optimum discriminant plane, where all data have been previously projected. Results obtained in the CIGRE test system are presented, showing that this method provides an efficient tool for online transient stability assessment of electric power systems.

Abstract
The versatility of Bewley's method for the calculation of transient currents and voltages using personal computers is shown. The computer time and storage required are relatively small. SOBBE program is shown to be an efficient program for the study of transient phenomena of medium-size power system networks. Numerical results are presented.

Abstract
This paper presents a new candidate method for on-line transient security assessment and enhancement based on pattern recognition techniques. Transient state variables are used as primary features and the classifier is obtained in two phases, through the combination of an optimum discriminant transformation together with a probabilistic procedure. The proposed security functions can be further refined by means of a second level classifier based on an optimal discrimination plane and using a weighted K nearest neighbor rule. It is shown that this method provides also an efficient and simple tool for on-line preventive control. Results obtained for several contingencies in the CIGRE test system are discussed.

Abstract
A candidate methodology for online transient stability assessment in power systems is presented. The method uses dynamic system variables as primary features. Linear security functions are derived by applying Fisher discriminant transformations and probabilistic considerations. Test results obtained on the CIGRE system are presented and discussed.

Abstract
The basic function of an electric power system is to satisfy the customer energy requirements as economically as possible and at an adequate level of continuity and quality. Reliability calculations such as those described in this paper can be used with advantage in establishing additional security constraints, that if used in the right context and backed up by the inevitable economic analysis, provide better and more consistent information for system planning or expansion studies. The model described can also be used when the simulation of the actual operating conditions is necessary.

Abstract