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The recently proposed techniques for detection and classification of different faults are amenable to statistical-based methods such as correlation or alienation coefficients. In this paper, an improved alienation coefficient-based classification algorithm is proposed. In the method, a modified alienation coefficient formula is suggested, by which different faults could be identified more accurately. Switching of heavy loads is also considered in the proposed algorithm. The performance of the method is evaluated by simulation of a typical power system in different conditions. The results confirm high capabilities of the proposed method for detection and classification of different faults. Furthermore, the results are verified using a low-scale test bench system in the laboratory. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Electric arc furnace (EAF) is a nonlinear and time-varying load that causes power quality problems such as voltage flicker and harmonics. Field measurement of voltage and current from EAFs in Mobarakeh Steel Company in Isfahan-Iran are used to introduce a comprehensive model for EAF. A new dynamic, nonlinear and time-varying model is presented here. In other words, the function between EAF voltage and current is nonlinear, differential and with time-varying parameters. By using the recorded data, the order of the dynamic part is determined by a new approach. The nonlinear characteristic is modeled with proper polynomial functions. All parameters related to the dynamic and nonlinear functions are considered time varying as time series. Autoregressive moving average (ARMA) models are implemented and the suitable ARMA order is attained for all EAF time-varying parameters. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a novel methodology for detecting fault conditions in the secondary side of electric arc furnace (EAF) transformer. The major focus of this study is to design a digital algorithm which uses solely the primary side current. Therefore, in this new methodology, only the primary side current is measured, and the fault presence in the secondary side is investigated. Here, there are two main objectives. The first objective is minimizing the fail-to-trip functioning probability, and the second one is minimizing the Mal-Trip operation probability. The fault characteristics are extracted using accurate simulation of EAFs installed in the Mobarakeh Steel Company (MSC) in Isfahan, Iran to fulfill the first objective. Three-phase field data of instantaneous current from the primary side of eight EAF transformers of MSC is also provided to evaluate performance of the proposed algorithm in the normal conditions and to achieve the second objective. The proposed algorithm is based on the sudden reduction of current harmonics in the fault conditions which is evaluated by a proposed special index which is called 'the difference function' in this paper. Overall reliability assessment (dependability and security) of the proposed protective scheme demonstrates that even in this highly varying and unpredictable environment, the proposed algorithm is so precise and fast in fault detection. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY With increasing penetration of wind turbine in power systems and micro grids, it is inevitable to investigate effects of wind turbines on micro-grid performance. This paper investigates the impact of doubly fed induction generator (DFIG) on transient stability of the micro-grid. In the first step; simulation results show that the more penetration of DFIG in a micro-grid, the less critical clearing time (CCT). In the second step, in order to improve the transient stability of the DFIG, a Fuzzy controller is introduced and added to the conventional proportional and integral (PI) controller of rotor side of the DFIG, which increases the CCT. In proposed algorithm, the speed and acceleration of the rotor are used as the inputs of the fuzzy PI controller. Numerical simulations on a typical micro-grid shows the benefits of the proposed controller. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: Delays in reactive power measurement and thyristor ignition limit SVC performance in flicker mitigation of electric arc furnaces (EAFs). To overcome this limitation, prediction methods can be employed to forecast the EAF reactive power for half cycle ahead, used as a reference signal of the SVC. The utilized prediction methods in this area can be divided into linear and black‐box approaches. However, the linear approaches cannot extract the nonlinear governed relations, and using a black‐box model is not efficient for linear relations. A Gray‐ANN method is proposed here to take the advantages of the two mentioned approaches. Results from indices based on actual records of Mobarakeh Steel Company confirm superiorities of the proposed method over previously utilized prediction methods in this application. Furthermore, SVC's flicker mitigation ability is evaluated using the actual data. The results confirm the significant reduction of flicker compared with the regular system. [ABSTRACT FROM AUTHOR]

Summary: Connection of distributed generations (DGs) to distribution networks changes their radial construction to mesh type and increases fault current level. In order to prevent over current relay tripping in case of out‐of‐zone faults, direction of faults must be determined. On the other hand, fault current limiters (FCLs) are a suitable technique to reduce the issue of fault current increasing. In this paper, it is confirmed that operation of FCLs affects voltage and current signals, drastically. Since fault direction is detected by directional relays using these signals, hence, FCLs can affect the performance of the relays. In the other hand, if the added DG is a wind turbine, it may affect the directional relays performance due to intricate fault behavior of wind turbines. To investigate the mentioned hypothesis, some of directional relaying algorithms are evaluated in presence of wind turbine and FCL. [ABSTRACT FROM AUTHOR]