MODELING THE PROTECTIVE SYSTEM FOR POWER-SYSTEM DYNAMIC ANALYSIS

Mathematical models for power system dynamic analysis including the dynamics of the protective system are presented. The formulation of the equations is based on establishing explicit relations between the protection system and the rest of system dynamic elements through the node admittance matrix Y-BUS. This relationship is achieved by representing the circuit breakers of interest as part of the transmission network elements. The protective relays, reclosing relays and circuit breakers are modeled as dynamic devices for tracking the dependence of these devices on the voltage and current inputs using the phasor state variables. A simple example illustrates the concepts. As a direct consequence of the analytical model, the concept of a protection success region is introduced and the implications for stability analysis, relay coordination, adaptive relaying and cascade tripping are discussed.