A maloperation case of busbar protection caused by a dead-zone protection abnormality in the Bra-zilian Midwest Grid on September 19th, 2012, is briefly described. The operation process of pilot distance, automatic reclosure, busbar differential and dead-zone pro-tection, and the emphasis on the logic scheme of dead-zone protection are analyzed. The time delay between thebreaker's main pole and auxiliary contact during reclosurewas the main cause in this case, and a defect in the logicallowed it to occur. The differences in deadzone protection logic between Brazil and China are discussed. A test platform was constructed in the laboratory, and a site simulated experiment was also performed. Possible causes are suggested and test activities are carried out to verifythem. Results show the values of practical engineering approaches to the solution. Experience also contributed to avoiding future mal-operations and streng thening the reliability of the protection system, and thus of the power supply in Brazil.