Application of PSCAD/EMTDC and Chaos Theory to Power System Ferroresonance Analysis

Ferroresonance is a nonlinear dynamic electrical phenomenon, which frequently occurs in a power system that comprises no-load saturable transformers, transmission lines (or cables) and single-phase switching with three-phase supply. Common characteristics of a nonlinear system are multiple equilibrium points, limit cycles, jump resonance and subharmonic generation. This paper presents an extension of PSCAD/EMTDC to analyze ferroresonance in the power system. Field tests were performed on two networks to identify the crucial factors in ferroresonance. EMTDC was then used to simulate the ferroresonance for the same network configurations and parameters. The accuracy of the modeling was verified with the results from the field tests. Analytical methods for nonlinear dynamic systems and MATLAB are used to obtain characteristic curves such as a time-domain waveform, phase-plane, and Poincaré section. Four modes of ferroresonance are shown for four different initial conditions. The brute-force calculation was employed to generate a bifurcation diagram. Sensitivity of resonance to voltage supply and load can be determined from the bifurcation diagram. The performance of MOV arresters exposed to ferroresonance in pad-mounted transformers is briefly discussed.