Modelling and performance testing of a digital over-current relay enhanced designed model




digital over-current relay, inverse and instantaneous characteristics, load starting current, primary protection, back-up protection


Introduction. The over-current relay is widely used to protect distribution and transmission electrical systems against excessive currents occurring due to short circuit or overload conditions. Many works have been carried out in the field of models simulation design of digital over-current relays in the literature, but unfortunately many of them are more complex design models, have very slow execution time and only work in simple faults cases. Purpose. The purpose of this work is to present the performance of a modified and improved model of a digital over-current relay designed in Simulink/MATLAB environment with more simplified design, faster execution time, and able to operate under more complex fault conditions. Methodology. Before starting tests, modelling of over-current relay is presented in details, of which the basic logics of the proposed model to implement inverse and instantaneous characteristics are well explained. Afterwards, various tests are carried out for the performance analysis of the enhanced designed relay model in terms of: operating speed for eliminating faults that has arisen, ability to distinguish between a fault current and load starting current, capacity distinguish between real and temporary fault currents, the way to manage variable faults over time, and the degree of harmony between primary protection relay and back-up protection relay. Originality. The originality of our proposed work consists in the development and improvement of a digital over-current relay model designed in Simulink/MATLAB environment in such way that it becomes able to operate under new harsh test conditions. This developed designed model is implemented and applied in a 400V radial distribution power system with a load that causes a starting current. Results. The obtained values of simulation are compared with the theoretically calculated values and known existing models. The obtained results after various tests validate the good performance of our enhanced designed model.

Author Biographies

H. Sekhane, 20 August 1955 University of Skikda; Constantine 1 University

Doctor of Electrical Engineering; Electrical Engineering Department; Laboratory of Electrical Engineering of Constantine (LGEC)

D. Labed, Constantine 1 University

Doctor of Electrical Engineering, Professor; Electrical Engineering Department; Laboratory of Electrical Engineering of Constantine (LGEC)

M. A. Labed, Constantine 1 University

PhD Student; Electrical Engineering Department; Laboratory of Electrical Engineering of Constantine (LGEC)


Prévé C. Protection of Electrical Networks. ISTE Publ., 2006. 508 p. doi:

Aman M.M., Khan M.Q.A., Qazi S.A., Digital Directional and Non-Directional Over-Current Relays (Modeling and Performance Analysis), NED University Journal of Research, 2011, vol. VIII, no. 2, pp. 70-85. Available at: (Accessed 12 March 2021).

Jhanwar V., Pradhan A.K. Accurate Overcurrent Relay Algorithm using Fundamental Component. 2008 Joint International Conference on Power System Technology and IEEE Power India Conference, 2008 pp. 1-4. doi:

Sidhu T.S., Sachdev M.S., Wood H.C. Design of a microprocessor-based overcurrent relay. [Proceedings] WESCANEX '91, 1991, pp. 41-46, doi:

Shah K.R., Detjen E.D., Phadke A.G. Feasibility of adaptive distribution protection system using computer overcurrent relaying concept. IEEE Transactions on Industry Applications, 1988, vol. 24, no. 5, pp. 792-797. doi:

Almas M.S., Leelaruji R., Vanfretti L. Over-current relay model implementation for real time simulation & Hardware-in-the-Loop (HIL) validation. IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society, 2012, pp. 4789-4796. doi:

Yacine A.A., Noureddine A.A., Hamid B., Farid H. Implementation of a Numerical Over-current Relay Using LabVIEW and Acquisition Card. 2018 International Conference on Electrical Sciences and Technologies in Maghreb (CISTEM), 2018, pp. 1-5, doi:

Alstom Grid. Network Protection & Automation Guide. May 2011. 508 p. Available at: (Accessed 12 March 2021).

Atwa O.S.E. Practical Power System and Protective Relays Commissioning. Elsevier, Academic Press, 2019. 398 p. doi:

Saleem A., Iqbal A., Mehmood K., Samad M.A., Hayat M.A., Manzoor U. Modelling and Implementation of Microprocessor Based Numerical Relay for Protection Against Over/Under Current, Over/Under Voltage. Journal of Computational and Theoretical Nanoscience, 2020, vol. 17, no. 2, pp. 1332-1338. doi:

Verzosa Q., Lee W.A. Testing Microprocessor-Based Numerical Transformer Differential Protection. IEEE Transactions on Industry Applications, 2017, vol. 53, no. 1, pp. 56-64. doi:

Donohue P.M., Islam S. The Effect of Non-Sinusoidal Current Waveforms on Electro-Mechanical & Solid State Overcurrent Relay Operation. 2009 IEEE Industry Applications Society Annual Meeting, 2009, pp. 1-6. doi:

Naga Sujatha K., DurgaRao R., Shalini V.B. Performance analysis of digital over current relays under different fault conditions in radial and parallel feeders. International Journal of Science and Technology, 2017, vol. 3, no. 1, pp. 146-158. doi:

Suliman M.Y., Ghazal M. Design and Implementation of Overcurrent Protection Relay. Journal of Electrical Engineering & Technology, 2020, vol. 15, no. 4, pp. 1595-1605. doi:

Pan Y., Steurer M., Baldwin T.L., McLaren P.G. Impact of Waveform Distorting Fault Current Limiters on Previously Installed Overcurrent Relays. IEEE Transactions on Power Delivery, 2008, vol. 23, no. 3, pp. 1310-1318. doi:

Maji P., Ghosh G. Designing Over-Current Relay Logic in MATLAB. International Journal of Scientific & Engineering Research, 2017, vol. 8, no. 3, pp. 40-43. Available at: (Accessed 12 March 2021).

Idris M.H., Adzman M.R., Tajuddin M.F.N., Amirruddin M., Ismail M.A. Auto-reclose Relay Simulation for Research and Education. 2018 4th International Conference on Electrical, Electronics and System Engineering (ICEESE), 2018, pp. 29-33. doi:

Ibrahim M.A., Ibrahim W.K., Hamoodi A.N. Design and Implementation of Overcurrent Relay to Protect the Transmission Line. International Journal of Engineering Research and Technology, 2020, vol. 13, no. 11, pp. 3783-3789. doi:




How to Cite

Sekhane, H., Labed, D., & Labed, M. A. (2022). Modelling and performance testing of a digital over-current relay enhanced designed model. Electrical Engineering & Electromechanics, (3), 71–78.



Power Stations, Grids and Systems