Identifying swing mode bifurcations and associated limits on available transfer capability

Analytic techniques for predicting onset of voltage collapse in power systems often rely upon identification of a saddle node bifurcation. While many authors acknowledge that the separation between voltage phenomena and phase angle phenomena is far from absolute, most recent works have viewed voltage variation as the more significant problem. The goal of the work presented here is to shift focus back to loss of stability mechanisms associated with phase angle behavior and electromechanical swing modes. We will exploit structural features in the network to identify a typical form for the eigenvector associated with a bifurcating "swing mode" that reduces in frequency and ultimately loses stability. In a simple case study, we demonstrate that the participation of angles in such a mode is greater than that of voltages.