Transient Stability Constrained Protection Coordination for Distribution Systems With DG

Abstract

Overcurrent relays are the main protective devices used in distribution networks. High relay operating times coupled with the low inertia time constant of distributed generations (DGs) can result in DG instability during fault clearance. This paper proposes a novel stability constrained protection coordination problem formulation that incorporates transient stability constraints for determining the optimal relay settings. A hybrid communication assisted protection scheme is optimally determined to satisfy both protection coordination as well as transient stability constraints. The proposed approach is tested on the IEEE-33 bus distribution system equipped with synchronous-based DG. Time domain simulations are performed to determine the critical clearing time curve for each DG to be incorporated in the protection coordination problem. The proposed approach is compared against conventional protection coordination.