IEC 61850 process bus - principles, applications and benefits

Modern distance protection relays are complex multifunctional devices based on classical or advanced operating principles that impose special requirements for their testing. The paper analyzes the functionality, the functional hierarchy and the schemes typically available in distance relays. It then discusses the methodology for testing of such relays. Testing of individual protection and non-protection elements, complex protection functions and communications based transmission line protection schemes is described in detail.