Transient stability investigations on a Brazilian network by SIME

The secure operation of the Brazilian power system calls for a fast and accurate transient stab ility method able to screen contingencies and scrutinize only the relevant ones. This paper explores the ability of SIME to meet such needs. SIME is a hybrid method coupling a particular direct approach with time-domain programs. It is designed so as to combine advantages of both : the ability of time-domain programs to handle any power system modelling and the computational efficiency of the direct method, its margin computation and critical machines identification. By exploiting these pieces of information, we devise a com pound made-to-measure procedure which in a sequence screens contingencies in terms of their critical clearing times and scrutinizes the most dangerous ones in terms of critical clearing times and/or power limits. The method provides substantial CPU time savings over a purely time-domain approach, without sacrificing to accuracy. The simulations performed on the Brazilian South-Southeast power system illustrate the method and its good performances.