On the Assessment of Sampling Rate Impacts on Responses of Digital Protective Relays

Power systems (including industrial and commercial power systems) widely utilize digital protective relays for component and system protection. These protective devices have shown numerous operational advantages over conventional electromagnetic protective devices. Such operational advantages include the accuracy, reliability, response speed, interoperability, weight, and size. Performance and operational advantages of digital protective relays are typically dependent on the resolution of their input data, as well as their algorithms for fault detection and identification. This paper assesses the performance of time-based, frequency-based, and time-frequency-based digital protective relays, when operated at different sampling rates. Tested sampling rates include low, medium, and high sampling rates that range from 16 to 288 samples per cycle. In this paper, the three digital protective relays are tested when deployed as the digital 87 T transformer digital protection. Performance of the time-based, frequency-based, and time-frequency-based digital protective relays is assessed in terms of their accuracy and response speed. Test results show that low sampling rates can deteriorate the accuracy and response speed of the three tested digital protective relays. Obtained performance results also reveal that medium and high sampling rates can effectively improve the accuracy and response speed of the time-based, frequency-based, and time-frequency-based digital protective relays.