Directional Overcurrent Relays Protection Schemes in Microgrids

Abstract

The high reliable operation of an electrical system network depends on the proper coordination of its protective relays that protect this system. The improper outage of any part in the protected electrical systems will affect its reliable operation. Definitely, each portion in the protected zones has primary protection and backup protection for providing a high level of security. Protection devices should be coordinated such that: primary protection will provide the first defense to clear the faulty section, and if it fails the backup protection should operate after a predefined coordination time interval to isolate the defective part without influencing the rest of the system. Designing directional overcurrent relays (DOCRs) protection schemes mandatory needs the important following data: Three-phase short circuit currents from the short circuit analysis, load flow analysis, relay pairs identification, and the current transformer ratio (CTR). In this thesis work, the load flow and short circuit analysis are obtained using ETAP software, the relay pairs are identified using a LINKNET algorithm.