Distance protection closed-loop testing using RTDS

This paper presents a distance protection test procedure by applying the Real-Time Digital Simulator (RTDS) of a power system. RTDS is a tool to design, develop, and test power-system protection. The RTDS enables real-time computation of electromagnetic phenomena with a calculation time step of even 50μs. The hardware allows the import and export of many signals from the simulator to an external real power-system component and, therefore, the so-called closed-loop testing. With this method, it is possible to get an insight into both the elements’ behaviour and the influence of these components on the power-system operation. The testing of a very simple impedance-protection function by the Schweitzer Engineering Laboratories protection relay is explained. Moreover, the effects of a DC offset have been tested on this relay. The test results emphasize the advantage of the RTDS for the determination of actual power-system components’ behaviour in various power-system conditions. The RTDS software, i.e. RSCAD, is used to simulate the power system models.