Interphase Fault Relaying Scheme to Mitigate Sympathetic Tripping in Meshed Distribution System

In a distribution system when fault occurs, prior operation of any other relay which is not designated as the primary relay causes undesired shedding of a healthy line. This phenomena of unwanted relay operation is termed as sympathetic tripping. For appropriate relay operation, issue of sympathetic tripping is required to be considered while addressing relay coordination problem. This paper proposes a phase fault protection scheme, which mitigates the issue of sympathetic tripping in the meshed network. The undesired relay operation in the network is restricted by imposing some additional constraints on the conventional relay coordination problem. The proposed nonlinear optimization problem is solved by using Shannon-Wiener differential evolution algorithm. Procured optimal relay settings will provide efficient protection against each phase fault without causing sympathetic tripping. The efficacy of the proposed algorithm is examined on modified IEEE-8-bus system, IEEE-14-bus system, and IEEE-30-bus system. The obtained results are verified by using GE Mutilin, model-750/760 overcurrent relay in ETAP (industrial simulation software).