Distributed generation (DG) brought new challenges for protection engineers since standard relay settings of traditional system may no longer function properly under increasing presence of DG. The extreme case is coordination loss between primary and backup relays. The directional overcurrent relay (DOCR), which is the most implemented protective device in the electrical network, also suffers performance degradation in the presence of DG. Therefore, this paper proposes the mitigation of DG impact on DOCR coordination employing adaptive protection scheme (APS) using differential evolution algorithm while improving overall sensitivity of relays. The impacts of DG prior and after the application of APS are presented based on interconnected 6 bus and IEEE 14 bus system. As a consequence, general sensitivity improvement and mitigation scheme is proposed.

The coordination of directional overcurrent relays is most commonly studied based on a fixed network topology within an interconnected power system. Due to its complexity and non‐linearity, the relay coordination is formulated as an optimisation problem. Distribution systems often suffer consequences due to the dynamic changes of network topology and operation of elements. Such changes are for example the inputs and outputs of generators, lines and loads. The consequences are reduction of sensitivity and selectivity of relays. The principal objective of this study is to coordinate the directional overcurrent relays based on adaptive protection scheme. The secondary objective is to present the formulation of ant colony algorithm and a comparison of it with the genetic algorithm.