This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON POWER DELIVERY 1 Maximum Performance of Electric Arc Furnace by Optimal Setting of the Series Reactor and Transformer Taps Using a Nonlinear Model Haidar Samet, Teymoor Ghanbari, and Jafar Ghaisari Abstract—In electrical arc furnaces (EAFs), an unstable arc leads to unfavorable operation of the EAF, which can be rectified by using series reactors. Installation of the series inductor affects some electrical parameters of the EAF, such as arc stability, power factor, arc length, and the EAF efficiency. Furthermore, it reduces the effective transferred power to the EAF. To achieve desired transferred power after installation of the series reactors, the secondary voltage of the EAF transformer should be increased. However, after any tap changing of the EAF transformer, arc stability and other relevant parameters are affected. So the impact on the EAF electrical magnitudes caused by changes in the series reactor and in the EAF transformer tap should be simultaneously studied. This research deals with a new method for optimal setting of the series reactor and EAF transformer tap to achieve the EAF best performance. Using a nonlinear model for the EAF, its electrical characteristics, at nominal transformer current and for all of the possible transformer and reactor taps, are calculated and the results are tabulated. Using these tables, the optimal setpoint for transformer and series reactor taps is determined in different conditions. Finally, the method is investigated from an economic point of view. Index Terms—Electric arc furnace (EAF), series reactor, stable arc, SVC, transformer tap. I. INTRODUCTION D UE to the rapid growth of steel demand, along with the de- velopment of the steel production industry, performance optimization of the existing plant to achieve maximum pro- duction has become more essential. In an electrical arc furnace (EAF), maximum production efficiency can be achieved in min- imum operation delays and production downtime conditions [1], [2]. This can be realized if available maximum power is ex- erted to the furnace in minimum time [3]. The series reactors are well known devices, utilized to improve the EAF perfor- mance [4]–[6]. These reactors are usually installed in series with high-voltage (HV) terminals of the EAF transformer and can be found in variable or fixed value types. Installation of the series Manuscript received February 02, 2013; revised December 09, 2013, April 22, 2014, and May 21, 2014; accepted July 03, 2014. Paper no. TPWRD-00145- 2013. H. Samet and T. Ghanbari are with the Shiraz University, Shiraz 7134851154, Iran (e-mail: Samet@shirazu.ac.ir). J. Ghaisari is with the School of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPWRD.2014.2336693 reactors in EAF improves the voltage flicker [5], [7] and arc sta- bility [8]–[10]. Although it is known that employing the series reactor can improve the arc stability and there is several types of research regarding arc stability, still there is not an exact answer about the optimized series reactor value. On other hand, after inserting the series reactor in the EAF circuit, the transferred power to the EAF decreases. By increasing the transformer tap, the trans- ferred power can be restored to the desired level. But an increase of the voltage affects the arc stability and other electrical param- eters of the EAF. Therefore, influences of both series reactor and transformer taps changing should be evaluated simultane- ously. This paper with a simple novel approach deals with the optimized selection of series reactor and transformer taps. With selection of the optimal setpoint of the reactor and transformer tap setting, EAF performance can be optimized in regards to arc stability, transferred active power to EAF, arc length, system ef- ficiency, and required reactive power. In this research, the electrical system of the Mobarakeh Steel Company (MSC) in Isfahan/Iran is considered for such study. In this factory, it was decided to substitute the old EAF trans- formers with new higher rating ones along with a series reactor in series with HV terminals of each transformer. Effects of the series reactor installation on different parameters of the EAF system are studied, and the results are tabulated in some tables. Based on these results, the optimum setpoint of the transformer and series reactor tap setting is determined. The series reactor and transformer have 7 and 21 taps, respectively. So, among 147 different cases, the optimal state should be determined based on some proposed criteria. The results achieved by this study are based on many recorded data. Three-phase supply voltages and currents of the EAFs were measured in the secondary side of the arc furnace transformers in scrapping, melting, and refining stages for several melting processes for three months. The recorded data cover 10 s of real-time operation of the EAFs. Each data set in- cludes a number of samples with 128- s sampling time. Based on the recorded voltages and currents, a nonlinear model for the arc furnace is utilized using Cassie formula [11], by which the optimum setpoint for the series reactor and transformer tap setting are derived. Though the proposed method is described by a typical case study, it can straightforwardly be employed in other EAFs. This paper is organized as follows: in Section II, the system under study and the utilized nonlinear arc furnace model are in- 0885-8977 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.