Abstract: DC protection system is the most important part in a UHVDC/HVDC project, and directly affects the gird safety. Generally, the redundant configuration principle is used in the protection system of actual UHVDC/HVDC projects. The paper discusses the reliabilities of the“two out of three” redundant configuration and the full duplication redundant configuration. Based on the original full duplication redundant configuration, an improved redundant configuration is proposed by improving the action logic. The improved redundant configuration can meet the demand of reducing the false tripping probability.