On high-voltage transmission, distance relays have the capability of serving both as primary protection and as remote backup protection. While the overcurrent relay (OCR) and the ground fault relay (GFR) function as a local backup in the event that the distance. Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 2 Abstract: Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems. Important benefits include limiting tripping to faulted. Abstract: Information on the concepts of protection of ac transmission lines is presented in this guide. To this aim, an RTDS®-based hardware-in-the-loop testing platform.