ABSTRACT
The authors have analyzed a lot of different types of the most up-to-date digital protective relays (DPRs) of the world's leading brands and finally found devices. Even a small company can enter the DPR market offering consumers a new concept of cheap and reliable relay protection, equipped with backup block modules. Unification of DPR modules will allow solving multiple problems under normal conditions of using and significantly increasing restoration of DPR after intentional destructive impacts. The use of two identical DPR sets is apparently inadequate to enhance the reliability of relay protection for critical objects, and it is wise to use three sets with output signal majorization based on "two out of the three" principle. The use of suggested criterion for measuring DPR reliability and of additional reliability data discussed earlier will make it possible to change the nature of relationships between DPR consumers and manufacturers and to enhance reliability of relay protection.
