Comprehensive study of transformer inrush current mitigation techniques

Subject Areas :

Amir Ghaedi ^{1 *}

1 - Department of Electrical Engineering, Dariun Branch, Islamic Azad University, Dariun, Iran

Received: 2025-04-19 Accepted : 2025-08-16 Published : 2025-09-21

Keywords: core material comparison, EMTP-RV, inrush current, transformer switching strategy, magnetic characteristic, energizing time, residual flux effect,

Abstract :

The transformer inrush current is the high amplitude and non-sinusoidal current occurred in the initial cycles after energizing the transformer. This current may result in some problems in the power system such as voltage drop, heat losses, power quality reduction and malfunction of the protective relays. To prevent malfunction of the protective system, the harmonic contain of this current is analyzed to recognize this current from the fault currents. However, the techniques that reduce the amplitude of the transformer inrush current can prevent from the disruptive effects of this current. For this purpose, in this paper a comprehensive study is performed on the novel techniques that can be used to mitigate the inrush current of the transformer. To this end, different magnetic materials used in the manufacturing of the transformer core, are considered and based on the related magnetic characteristic, the amplitude and the harmonic content of the produced inrush current are determined using of the EMTP-RV software. To select a suitable magnetic material for transformer core, a comparison among these magnetic materials is performed. In addition, other techniques used for mitigation of the transformer inrush current including the time of the transformer energizing, residual flux and transformer loading are used and their impact on the transformer inrush current is investigated using of the EMTP-RV software.

References:

[1] Wu, Li-Cheng, et al. "The effect of inrush current on transformer protection." 2006 38th North American Power Symposium. IEEE, 2006.
[2] Abdulsalam, Sami G., and Wilsun Xu. "Analytical study of transformer inrush current transients and its applications." IPST Conference, Montreal, Canada. 2005.
[3] Gong, Maofa, et al. "A Method for Identification of Transformer Inrush Current Based on Box Dimension." Mathematical Problems in Engineering 2017.
[4] Cui, Yu, et al. "A sequential phase energization technique for transformer inrush current reduction-Part I: Simulation and experimental results." IEEE Transactions on power delivery, vol. 20, no. 2, pp. 943-949, 2005.
[5] Xu, Wilsun, et al. "A sequential phase energization technique for transformer inrush current reduction-Part II: theoretical analysis and design guide." IEEE transactions on power delivery, vol. 20, no. 2, pp. 950-957, 2005.
[6] Cardelli, Ermanno, Antonio Faba, and Francesco Tissi. "Prediction and control of transformer inrush currents." IEEE Transactions on Magnetics, vol. 51, no. 3, pp. 1-4, 2015.
[7] Faiz, Jawad, and Saeed Saffari. "Inrush current modeling in a single-phase transformer." IEEE Transactions on Magnetics, vol. 46, no. 2, pp. 578-581, 2010.
[8] Kovan, Baris, et al. "Mitigation of inrush currents in network transformers by reducing the residual flux with an ultra-low-frequency power source." IEEE Transactions on Power Delivery, vol. 26, no. 3, pp. 1563-1570, 2011.
[9] Ma, Jing, et al. "Identifying transformer inrush current based on normalized grille curve." IEEE Transactions on Power Delivery, vol. 26, no. 2, pp. 588-595, 2011.
[10] He, Benteng, Xuesong Zhang, and Zhiqian Q. Bo. "A new method to identify inrush current based on error estimation." IEEE Transactions on power delivery, vol. 21, no. 3, pp. 1163-1168, 2006.
[11] Azizan, N. S., et al. "Medium sized industrial motor solutions to mitigate the issue of high inrush starting current." AIP Conference Proceedings. Vol. 2339. No. 1. AIP Publishing LLC, 2021.
[12] Habyarimana, Mathew, Remmy Musumpuka, and D. G. Dorrell. "Mitigating in-rush currents for induction motor loads." 2021 IEEE Southern Power Electronics Conference (SPEC). IEEE, 2021.
[13] Szelag, Wojciech, Cezary Jedryczka, and Mariusz Baranski. "A New Method of Reducing the Inrush Current and Improving the Starting Performance of a Line-Start Permanent-Magnet Synchronous Motor." Energies, vol. 17, no. 5, 1040, 2024.
[14] McLyman, Colonel Wm T. Transformer and inductor design handbook. CRC press, 2017.
[15] Chan, H. L., et al. "Study on magnetic materials used in power transformer and inductor." 2006 2nd International Conference on Power Electronics Systems and Applications. IEEE, 2006.
[16] Hilzinger, Rainer, and Werner Rodewald. Magnetic materials: fundamentals, products, properties, applications. Vacuumschmelze, 2013.
[17] EPCOS, AG. "Ferrites and accessories-SIFERRIT material N87." Data Sheet, September 2006.
[18] Handbook, Ferroxcube Data. "Soft Ferrites and Accessories.", 95, 2009.