Description, setting and secondary testing of a digital protective relaying system

The aim of this paper is to present the operation and utilization of a digital protective system for power subsystems, which consist of a power generation unit and a transmission line. The specific protective system has been designed and developed by the Greek company “PROT.A.S.I.S SA” [1] and is established in the electric energy systems laboratory of the School of Electrical & Computer Engineering at the National Technical University of Athens (NTUA). In particular, the procedures of setting and testing the SEL-587 and SEL-311B digital relays of “Schweitzer Engineering Laboratories, Inc.” company [2] are described. For this purpose, several short-circuit studies were carried-out at different locations of the studied power networks and then the setting parameters were calculated and loaded to the digital relays, using the AcSELerator Quickset® software [2]. In addition, the relays´ secondary tests were conducted utilizing the OMICRON CMC 356 device of the “OMICRON electronics GmbH” company [3] and the results are used to verify the proper and prompt response of their protection elements. Finally, the prospect of utilizing this laboratory protective system for research in adaptive protection schemes, for modern distribution networks with high penetration of distributed generation, is discussed.