Implementation and characterization of a numerical distance relay using a relay test-bench on RTAI-Linux platform

This paper deals with the implementation, evaluation and characterization of a numerical distance relay using a laboratory relay test-bench implemented on real-time application interface (RTAI)-Linux platform. The numerical distance relay has been realized on RTAI-Linux platform based on the full-cycle recursive discrete Fourier series algorithm. This relay provides a selectable relay characteristic such as Mho or Quadrilateral or Elliptical characteristic. The relay test-bench not only can be used to obtain steady-state relay characteristics, but also facilitates to generate any fault signals to perform dynamic testing of the relays. In this paper, Mho and Quadrilateral type numerical relay characteristics have been chosen for demonstration. It is found that such an experimental setup provides a hardware-in-the-loop facility in the lab environment to enhance the understanding about protective systems and thereby augmenting the classroom learning.