1. Basic components of digital protective relays -- 2. Design and functional modules of digital protective relays -- 3. Problems with the reliability of digital protective relays -- 4. Logic inputs in digital protective relays -- 5. Problems with output electromechanical relays -- 6. Problems with external power supplies -- 7. Testing digital protective relays -- 8. Electromagnetic intrusions on digital protective relays -- 9. Alternative (Nondigital) protective relays -- 10. Problems with international standards -- 11. New concepts for DPR design.