Abstract
This paper presents works involving developments of a real-time simulation laboratory of digital relay systems used for transmission system protections, based on RT-Lab. These relay models are designed to facilitate the investigation and evaluation of the protection system. A practical 345KV 72.8 km transmission line of Taiwan Power system is constructed to verify operations of differential relays and distance relays. Dynamic responses under various fault scenarios are verified. Simulation results of these tests show that the developed relay models operate correctively for various events. Also, the program execution time can be significantly reduced in comparison with results obtained from off-line Matlab/Simulink simulations.