The Gramian method to study of the stability of bilinear systems and the new technique of Gramians calculation is investigated. The method of early warning about the loss of stability of the electric power system is proposed. The method is based on the nonlinear process original predictive model. It is shown that the suggested approach has a transparent physical interpretation, i.e., stability loss risk corresponds to the energy of ill-stable modes group. The predicting model is developed based on associative search technique for nonlinear dynamic plants.