A study on the optimization over-current relay setting value considering the effect of a high penetration rate of distributed generation on distribution protection system

Recently, the research on hosting capacity (HC) calculation has become important due to the high interconnection of Renewable Energy Sources (RESs). The existing research on the maximum HC calculation is mainly focused on power quality. However, if the distributed generation is connected based on the HC calculation, there is a risk that the protection system could be affected and create some problems such as Sympathetic Tripping and Protection Blinding (protection device malfunction). Although this problem can be overcome by changing the relay correction value, the problems might still occur due to the limitation of the protection device setting. Therefore to solve this problem, an algorithm that can simultaneously optimize the Time Dial Setting of the overcurrent relay and the HC of the distributed generation without causing a protection system problem is proposed in this paper. The proposed algorithm was optimized through the most widely used genetic algorithm (GA), and the simulation was done using MATLAB and DigSLINET PowerFactory. The simulation was tested in IEE 37 bus system and from the simulation, the optimal overcurrent relay setting and HC value are obtained.