  In this paper, we develop a methodology for finite time rotor angle stability
analysis using the theory of normal hyperbolic surfaces. The proposed method
would bring new insights to the existing techniques, which are based on
asymptotic analysis. For the finite time analysis we have adopted the Theory of
normally hyperbolic surfaces. We have connected the repulsion rates of the
normally hyperbolic surfaces, to the finite time stability. Also, we have
characterized the region of stability over finite time window. The parallels
have been drawn with the existing tools for asymptotic analysis. Also, we have
proposed a model free method for online stability monitoring.
