An Analytical Adequacy Evaluation Method for Distribution Networks Considering Protection Strategies and Distributed Generators

Reliability evaluation relates to the impact of faults on customer outage frequency and time. Thus, studying the process of fault isolation and supply restoration is critical in reliability evaluation. In distribution systems, distributed generators (DGs), especially renewable DGs, are increasingly integrated into the network. New issues emerge after DG integration: 1) DG reliability model; 2) change of protection strategy and supply restoration process; and 3) islanding operation. In this paper, an analytical method is proposed to assess the distribution system reliability level considering these issues. The reliability model for DG and load are developed using scenarios reduction techniques based on historical data. The correlation between renewable resources and load is also formulated in the model. When a fault occurs in a distribution system, parts of the distribution system can be operated as islands. The reliability indices of the load point in the microgrid vary according to the power adequacy assessment in the island and supply restoration process. To improve calculation efficiency, the analysis of fault isolation and supply restoration process and reliability evaluation is based on segments instead of single components. Then, the overall reliability evaluation framework is proposed. In the end, a detailed case study is presented.