Protection Enhancement in Modern Distribution Networks Considering On-Load Tap Changer Operations Side-Effects

This paper shows that since high penetration level of distributed generations (DGs) makes the protection coordination complicated in active electrical grids, selectivity task among relays pairs can be easily affected by on-load tap changer (OLTC) tap position. Therefore, mitigating the side effect of OLTC tap position on relays coordination in active distribution networks is of crucial importance which should be considered in relaying process. To tackle this challenging issue, this paper presents a protection scheme based on deployment of numerical relays and low bandwidth communication links besides considering OLTC tap position. The proposed approach provides a selective scheme with individual settings for relays which are set independent from OLTC tap positions. The relays settings are obtained through the optimization process to minimize the relays tripping times. In this regard, a new logarithmic objective function (OF) is also presented to steer the relays setting toward optimal solutions with fast convergence. The feasibility and the effectiveness of the proposed formulation is tested on the IEEE 14-bus test system.