Iranian Journal of Power Engineering

Iranian Journal of Power Engineering

Intelligent Coordination of Directional Relays for Protection of Radial Distribution Systems with Integrated Distributed Generation

Document Type : Original Article

Author
Khuzestan Regional Electric Company, Ahvaz, Iran
Abstract
The integration of Distributed Generation (DG) into radial distribution networks introduces significant challenges for traditional overcurrent protection schemes, particularly with respect to relay–fuse coordination and fault selectivity. Variations in both the direction and level of fault currents caused by DG units can compromise the reliability of conventional recloser-based protection strategies. To address these challenges, this paper proposes an alternative protection approach in which directional overcurrent relays are deployed along the feeder, eliminating the dependence on a single recloser at the substation. The proposed scheme ensures selective fault isolation under different DG operating conditions and supports both fuse-saving and fuse-blowing protection philosophies. Unlike conventional approaches, the coordination logic remains effective regardless of the connection or disconnection status of DG units. The effectiveness of the proposed protection strategy is demonstrated through detailed time-domain simulations carried out on a representative radial distribution network using DIGSILENT PowerFactory. Simulation results confirm that the proposed method enhances coordination robustness and fault selectivity while maintaining compatibility with existing distribution protection infrastructure.
Keywords


Articles in Press, Accepted Manuscript
Available Online from 28 September 2026