Abstract—Many large scale system blackouts involve relay misoperations. Technical advancements in relaying technology has replaced the concept of specific relay for specific action with digital multifunction relays where only single relay can perform different types of relaying functions with the help of digital processor programming. Traditional relay algorithms and settings need to be evaluated under variety of fault and nofault system wide scenarios to better understand the cause of misoperation of relays. The fault diagnosis algorithm also need to be developed to assure improved relaying performance and then evaluated under various system conditions. This paper presents a novel digital multifunction relay based on Smart Discrete Fourier Transform Algorithm (SDFTA) that derived from Discrete Fourier Transform (DFT) which can estimate exact magnitude of DC offset component and completely eliminates it from operating quantities during faults and also makes use of smoothing window to filter out noise if any. The proposed digital multifunction relay’s performance is tested on 6-bus power system with the data generated by EMTP/PSCAD. The results had shown the efficient operation of the proposed SDFTA based digital multifunction relay.

Index Terms—Misoperation, digital protection, multifunction relays, filtering algorithm, decaying DC offset component, faults, phasor measurement, fault location.

*Professor in EEE Dept., St. Ann’s College of Engg. & Tech, CHIRALA-523187 , INDIA E-mail: sureshperli@yahoo.com
**Professor in EEE Dept., JNTU College of Engineering, Kukatpally, Hyderabad-500082, INDIA. E-mail: svjkumar101@rediffmail.com

Cite: P. Suresh Babu and Dr. S. V. Jayaram Kumar, "A Smart Discrete Fourier Transform Algorithm Based Digital Multifunction Relay for Power System Protection," International Journal of Computer and Electrical Engineering vol. 3, no. 1, pp. 66-73, 2011.