Non-adaptive over current relay coordination in distribution systems

Over current relay coordination in a meshed distribution system with multiple distributed renewable energy sources (RES) is a very challenging for the protection engineers. The exiting over current relays in the distribution system is set for some predefined network topology and fault currents. Connection of RES results change in network topology and causes additional fault current contribution from these power sources in the distribution systems. The contribution of fault currents from incoming RESs under changed network topology results in mal-operation of over current relays. Modifications of the existing over current relay settings for each new incoming RES is not practically feasible in field. Fault current limiters (FCL) have the capability to block the fault current under fault duration and offers very low resistance to the normal load currents in the distribution systems. This feature of FCL is utilized in this article to restore the over current relay coordination in the distribution system under RES penetration. These FCL devices will eliminate the impact of fault currents on the exiting over current relay coordination in the distribution systems. So, this is a non-adaptive type of over current relay coordination protection scheme, in which the settings of over current relay are not changes as per the injection of RES. The proposed non-adaptive over current relay coordination approaches is implemented in 33 KV distribution side of for IEEE 30 bus system.