For satisfying the demand of fast clearing fault on Middle-low Busbar, an over-current block protection approach for is proposed. The typical short circuit faults on middle-low voltage busbar are analyzed. With the advantage of GOOSE networks in the substation, a novel-type middle-low voltage busbar protection is designed. The details of the process of protection design and handling communication interrupt are presented. The effectiveness and reliability of the proposed approach are validated by practical application in a smart substation.