Impact of Distributed Generation on Reliability Evaluation of Radial Distribution Systems Under Network Constraints

Interest in distributed generation (DG) arose in the 1990s with the deregulation of the electricity industry and the development of improved DG technologies. Furthermore, the appearance of high-technology loads requires an increase in the reliability of the power system. In this new scenario, it is important to consider DG in the planning of distribution networks. For example, a utility can install DG to provide additional capacity to feeders or substations. Additionally, DG can be used to improve the restoration capability of the distribution networks, that is, DG can eliminate network constraints (voltage drop or feeder loading) during the restoration process. Consequently, DG can improve the reliability indices associated with the restoration time. In this paper, a methodology to estimate the impact of DG on the reliability indices of distribution networks is proposed. This impact is assessed considering that DG can be connected to an isolated feeder (isolated operation) or to a feeder with tie-lines (interconnected operation). The network constraints model used in this paper is based on a simplified version of the power summation load flow method and compensation techniques. The results with the proposed methodologies, to model the isolated and interconnected operation of DG, demonstrate that DG has a significant impact on the reliability indices of distribution networks. The proposed methodologies have been validated and tested in a large distribution test system. The results show the importance of considering the impact of DG on the reliability indices of distribution networks