Electrical Engineering Department
BS in Electrical Engineering
To better prepare students for careers in the electric power industry, specifically in the discipline of power system protection, the Electrical Engineering Department at Cal Poly San Luis Obispo proposed an initiative calling for the creation of new laboratory curriculum that uses microprocessor-based relays to give students hands-on experience in the application of protection theory. This report describes the creation of a system that meets this need by providing a laboratory-scale power system that demonstrates the use of common protective relays and protection schemes. This system provides a platform for laboratory coursework using protective relays for transmission line, transformer, and induction motor protection. Within this laboratory system, one of the primary goals of the project was the integration of the SEL-311L Line Protection Relay and the SEL-710 Motor Protection Relay as part of the overall protection scheme.
Development of the project was completed successfully, producing a protection scheme that protects power transmission equipment and the induction motor in both radial and bidirectional systems. The system clears all desired fault types and abnormal operating conditions with primary protection elements for each piece of equipment, as well as time-coordinated backup protection system-wide. The completed protection system is selective, removing only the minimum amount of power equipment necessary to clear fault conditions. It is also secure, in that normal operation does not result in unnecessary trips, and reliable, in that all fault conditions are cleared even when primary protection devices do not operate. The SEL-311L and SEL-710 relays were implemented successfully, and used to demonstrate more complex and advanced protection methods than simple overcurrent elements, such as permissive overreach transfer trips and motor thermal modeling.