Investigation of renewable energy based DG impacts on protection relay operation

Distribution network is mostly radial in nature and all loads are connected to the power grid through the distribution network. Maximum number of faults in power system occurs in the distribution network. Protection of distribution network is dominated by overcurrent (OC) protection application. With the intention to reduce greenhouse gas (GHG) emission, different types and size of renewable energy (RE) sources are now integrating into the power grid and most of these distributed generators (DG) are connecting near the load. These small scale distributed RE sources are effectively supporting the local loads and supplying excess electricity to the main grid. Most popular RE sources are solar and wind. When these sources generate at its peak capacity, the local load demand may remain less and therefore most of the generated electricity goes to the grid. OC relays placed at the upstream of the distribution line are set based on the current value through the line. Once this level of current value changes the performance of the OC relay may face challenges. This paper investigated the challenges of RE based DGs on the protection relay performance and proposed a relay operation algorithm to overcome these challenges. The result shows that with this approach same relay can adapt and operate under different network conditions.