Abstract: The protection configuration and charge control logic of LFP-901B extrahigh voltage digital fast line protection equipment were introduced. Once the charge circuit did not charge after reclose circuit act, and this caused the protection equipment act incorrectly. The fault was analyzed. The defect of charge circuit of the equipment and the hazard caused by HHKK value of zero were pointed out. Aiming at the defect of the charge circuit, some suggestions and rectification measures were put forward.

Key words: protection configuration, charge control logic, defect of charge circuit, reclose, hazard