Impact of renewable energy integration on overcurrent protection in distribution network

Renewable energy's grid-integration will strongly influence 3-sectional overcurrent protection's correct operation in distribution network because of its in feed current effect or shunt effect. Firstly, the fault current characteristics of different types of renewable energy sources are simulated, and their impacts on overcurrent protection are analyzed. Secondly, the detailed influence factors, including the renewable energy capacity, the integration location, the fault location, the reliability coefficient and the transmission line length, are thoroughly discussed in the distribution system model. Especially, by changing the renewable energy source capacity, the relationship between the short-circuit capacity ratio at the integration point and the fault current flowing through the protection is investigated. Lastly, simulation results on PSCAD/EMTDC show that when the short-circuit capacity ratio at the integration point is superior to 11.72%, the instantaneous overcurrent protection (1st section) will mal-operate, and when the ratio surpasses 21.8%, the time-delay instantaneous overcurrent protection (2nd section) will mis-operate.