An Optimization-based Protection Strategy in Active Distribution Network using Double Dual-Setting Directional Overcurrent Relays to Increase DG Penetration

Coordination between protection devices is one of the important issues in any protection scheme of an electrical power system. The tendency to increasingly use distributed generation has jeopardized the selectivity of overcurrent relays in active distribution networks. To increase the penetration level of distributed generation in these networks, an increase in the Protection Coordination Index (PCI) of the network is a must. For this purpose, in this paper, voltage-current-time characteristics and Dual Setting Directional Overcurrent Relays are used. In this case, coordination is not a trivial task and imposes further complexity. Since Dual Setting Directional Overcurrent Relays are capable to break current in both directions with separate tuning, they have the flexibility to improve the protection coordination index. Moreover, voltage-current-time characteristics employ voltage in the operation of relays. This capability can also be used in reducing the optimization of the protection scheme and provides more flexibility in coordination procedures. Afterward, the protection scheme is developed by user-adjustable voltage-current-time characteristics to improve the PCI as much as possible. The proposed scheme is modeled as a nonlinear programming approach which is solved by a Genetic Algorithm (GA).