Study On Probabilistic Security Measures Of Transmission Line

Security is always the first concern of the operation of power systems, thereby the securityanalysis, the target of which is to improve the stability and security of power systems, is one ofthe active research areas. Because of uncertain factors such as randomicity of electric power faultsand disturbance of loads, essentially dynamic security analysis of power systems is not andeterministic problem but a stochastic problem. Traditional methods of dynamic security analysisof power systems, which do not consider the effects of probability, have some limitations. Thesecurity analysis of power systems of probability has made many achievements, but the problemof huge calculation has not been well solved. Recently, we have made plenty of achievements of research in Dynamic Security Region ofpower systems. Based on those achievements this dissertation presents a dynamic security indexconsidering the effects of probability to solve the problem of huge calculation brought by thesecurity analysis of probability. At the same time the presented index considers the uncertainty ofthe fault type, the fault position and the fault resistance of transmission line as well as randomdisturbance of loads. It indicates the whole security level of the power systems and presents theabundant instructive information for security operation of power systems. In spite of this, large numbers of Dynamic Security Region are still needed to be calculated toget this index . So how to get its short cut calculation becomes the key aspect of the problem.Therefore, this dissertation makes a thorough study of the interrelation of the Dynamic SecurityRegions when the fault type, the fault position and the fault resistance are different. By means ofplentiful simulation analysis, we find two important properties of Dynamic Security Region oftransmission line: 1. When the fault type and fault position are given , the correspondinghyperplanes of Dynamic Security Region of different fault resistances have an extraordinary goodparallel property. 2. To the same transmission line, when the fault resistance is given, thecorresponding hyperplanes of Dynamic Security Region of different fault positions have a goodparallel property. Based on the above two properties, this dissertation presents the short cut calculation ofdynamic probabilistic security index which greatly saves the computation time. The illustratedexamples indicate that the precision of the proposed short cut calculation can basically meet theengineering demand.