Development of a relay test bench and an arbitrary waveform generator in RTAI-Linux platform

This paper presents the development of a PC-based relay test bench and an arbitrary waveform generator using an open-source Real-Time Application Interface (RTAI) in Linux environment. Such a setup not only permits the generation of any arbitrary waveforms: steady-state signals as well as transients, but also simplifies the testing of various single-phase or three-phase static relays such as over-voltage relay, directional power relay, negative sequence relay as well as numerical impedance relays. The actuating signal is fed to the relay under test using a set-up that consists of a PCI card with a built-in Digital to Analog Converter and a feedback circuit for detecting the status of the relay. Using any off-line simulation package, sampled data points of a desired waveform are obtained in the form of a data-file. The RTAI-Linux program generates this waveform in real-time which is directly fed to the relay under test. The relay test bench presented in this paper is a cost-effective set-up for laboratories to test and understand the behavior and characteristics of relaying systems.