Real time digital power system simulator design considerations and relay performance evaluation

Environmental pressures, right of way problems for new transmisson lines, large scale system interconnection and increasing power demand especially in developing countries call for new transmission technologies. Use of FACTS and HVDC is gaining momentum. Relaying problems in such systems require sophisticated approach and numerical technology using high grade processors offers a promising solution. To establish the performance of such relays which are designed more as powerful schemes rather than as a conglomeration of individual relays, detailed testing is required using an elaborate real-time simulator model. These tests are not only necessary during design and development but also are required by the utilities as a part of their acceptance. Highlighting the requirements of a hybrid real-time simulator including the complete spectrum of power system dynamics, this report describes an analog cum digital model used for real-time assessment of system performance. SVCs, HVDC, ASC and CSC can be modelled fully digital by computer simulation and transient real-time data injection as well as analog by using physical simulation with original converter controllers for performance evaluation of numerical relays under real system conditions. As an example of the use of this simulator, tests on a numerical EHV-line relay are described and the relay performance is analyzed.