A Coordinated Multi-Element Current Differential Protection Scheme for Active Distribution Systems

This paper introduces a current differential protection scheme, appropriate for application in medium voltage active distribution systems, where it is desired to keep the greatest possible number of loads and DG units energized during fault. Conventional two-terminal percentage relays are used form successive, time-current-coordinated, zones. Multiple time-delayed elements each zone guarantee coordination with zone's lateral devices, as well between successive Sensitive protect against relatively high-resistance faults, while instantaneous minimize speed whenever possible. Additional emergency deal post-fault topology changes breaker failure conditions enhancing overall scheme's performance. The proposed scheme applied model real system distributed generation, considering ring operation. A detailed simulation-based study proves applicability enhanced performance scheme.