Avaliação da criticidade estática e dinâmica de subestações em sistemas elétricos de potência

Abstract

This thesis presents new methods to classify nodes and substations based on static and dynamic (transient stability) network performances in electrical power systems. The approach is capable of offering a ranking of nodes (i.e., buses) or substations, whereby planners and system operators identify the facilities most likely to receive new reinforcements (i.e., investments). From the static point of view, the assessment of the nodal criticality is based on the analysis of all possible “N-1” and “N-2” contingencies with their respective probability of occurrence, considering only equipment directly connected to the corresponding bus. This process is repeated for all nodes. The amount of load shedding obtained by an optimal power flow and the related event probabilities are used as the basis for estimating the static index for each system node. From a dynamic point of view (i.e., transient stability), nodes are classified based on stability indices, which measure the impacts of single- and three-phase events (i.e., short-circuits) involving single contingencies of equipment connected to a given system node, focusing on an approach that improves the consistency and accuracy of the Single Machine Equivalent (SIME) method. The impacts of these events are also weighted by associated probabilities. The nodal criticality evaluation is also extended to substations, basically consisting of identifying the transmission elements and nodes that make up a substation, through a network topological algorithm, and how their failure is combined in the calculation of static and dynamic indices, for ranking the performance of network substations. With the support of this methodology, Special Protection Schemes (SPS) are implemented in order to improve the stability of the network. Several applications in test systems are performed to confirm the criticality of network equipment. Finally, conclusions are drawn and proposals for future work are discussed.