Dynamic state estimation assisted posturing for generator out-of-step protection

Protective relays used in power system today measure external signals to diagnose the internal state of the equipment they protect. Based on measurements of voltage, current, frequency at the bus, the decision is made whether the equipment is healthy or faulty. Due to advances in sensing and computing, it has become possible to use the external measurements to dynamically estimate the internal state of an equipment in real time, thus achieving better insight into its status. Motivated by this emerging paradigm, this paper proposes a dynamic state estimation (DSE)-enabled algorithm to improve protection functions for large synchronous generators during out-of-step conditions. The DSE module is developed using a phasor measurement unit (PMU)-assisted particle filter. The estimated electromechanical state (rotor angle) and voltage phase angle of the high voltage-side of the step-up transformer are used as inputs to detect the out-of-step (OOS) events. Initial results of numerical simulations conducted on a 10-machine, 39 bus test system demonstrate the feasibility of the proposed concept, and show the potential to monitor and supervise the conventional protection device from misoperations.