Abstract Heavily loaded, stressed power systems exhibit complex dynamic behavior such as auto and hetero parametric resonances and inter-area oscillations when subjected to a disturbance. These behaviors cannot be analyzed by conventional linearization-based methods. Nonlinear tools, such as normal form and modal series methods can be utilized for studying and understanding these complex behaviors. In this paper, using modal series technique, the effect of fault location and duration on the dynamic performance of stressed power systems is investigated. Three indices are defined and used to explain the effect of different fault scenarios on the transient behaviors of the system. Also, a qualitative analysis of plant mode and inter-area mode type behaviors are presented and typical differences are highlighted. The numerical simulations on the IEEE 50-Generator test system demonstrate validity of the study carried out by modal series analysis.
