Optimizing DG penetration in distribution networks concerning protection schemes and technical impact

Distributed generators (DGs) provide many benefits for distribution networks, however they increase the fault current level and cause miscoordination between the protective devices. This paper presents a framework to determine the optimal locations and permissible capacity limits of inserting DGs in the distribution system using the genetic algorithm (GA). A multi-objective function is developed based on the overall maximum capacity of DGs, voltage enhancement, power loss reduction, and fault current level. The optimization process considers the voltage level and protective-devices coordination as two main constraints. The coordination constraint including fuse-recloser and recloser-relay schemes is added to the multi-objective function in an augmented fitness function. Furthermore, the effects of modifying the setting of overcurrent relay on the DGs capacity are investigated. The proposed framework has been implemented on a typical 11 kV overhead distribution feeder. The results show the possibility of integrating large DGs and achieving considerable loss reduction, voltage profile improvement and fault current reduction without replacing the existing protection systems.