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Increasing the penetration level of distributed generation (DG) units in radial power distribution systems can increase the short-circuit level in these networks, which can, in turn, have destructive effects such as exceeding the tolerable current of the equipment and disrupting the protective coordination in the network. The active superconducting fault current limiter (ASFCL) is a new device that can limit fault current using voltage series compensation. This paper discusses the modeling of ASFCL and control strategies including fault detection and converter performance in normal and fault modes. Initially, its performance in limiting the fault current is investigated by simulating a sample three-phase system with ASFCL. In the next step, three operating modes including normal mode, upstream fault mode, and downstream fault mode are proposed to achieve an adaptive FCL that solves these problems in gridconnected microgrids. The simulation results confirm the proper performance of the ASFCL modes in both fault current limiting and protective coordination of overcurrent relays in the network. [ABSTRACT FROM AUTHOR]

Active superconducting fault current limiter (ASFCL) is a new type of FCLs which can limit the fault current at different levels. It also has a particular ability to compensate for voltage series in the electrical power systems. In this paper, an optimal coordination method is proposed to calculate both optimal setting parameters of overcurrent relays (OCRs) and limiting the impedance of ASFCL. The optimal parameters of OCRs are obtained using the maximum pickup current and minimum trip time method. In the next step, by applying a new DG unit to the microgrid, the optimal limiting impedance of ASFCL is obtained so that all OCRs could be coordinated without changing the relay setting parameters. Using MATLAB software, a typical distribution system connected to a microgrid with ASFCL is simulated and the simulation results are evaluated in terms of the fault current limitation and OCRs coordination. Simulation results confirm the appropriate performance of the proposed ASFCL for the above-mentioned purposes. [ABSTRACT FROM AUTHOR]

An accurate inter‐circuit fault location algorithm for double‐circuit transmission lines compensated by a generalized unified power flow controller based on phasor analysis is presented. The proposed algorithm utilizes synchronous currents and voltages of the buses on both sides of the line to accurately calculate the fault location. Using the equations of sequence component circuits, the algorithm calculates voltage and current of the fault point on both circuits. Then, using boundary conditions equations for 98 types of inter‐circuit fault on the double‐circuit transmission lines, the accurate location of the fault is obtained. The number of boundary conditions equations varies depending on the type of faulty phases of the two circuits and the number of unknowns in the current and voltage equations of the fault point. The calculation of these boundary equations are also described. The results presented in the simulation section verify the validity and accurate performance of the proposed algorithm under different fault conditions. [ABSTRACT FROM AUTHOR]

Summary In this paper, a communication‐based selective protective scheme using the combined adaptive cumulative sum algorithm (CACUSUM) is proposed, which can be used in wide‐area protection of multi‐terminal high voltage direct current (MT‐HVDC) transmission lines. The proposed algorithm works in the time domain and uses the variation pattern of the magnitude of line currents and bus voltages for fault detection. Simulation is done in MATLAB program using a test four terminals meshed HVDC transmission system. As a robust fault detector, the proposed approach detects fault occurrence as well as determining faulty zone, either faults on the DC line or AC part of the HVDC system; the whole in less than 2 ms. Simulation results confirm the robustness of CACUSUM performance against different fault resistances and different fault locations as well as the presence of noise in the signals. Appropriate speed, adaptivity, independence from system parameters, low sampling rate, low computational burden, simplicity, no need for any complicated hardware, and ability to detect cross faults are the significant benefits of this method in comparison with other ones. [ABSTRACT FROM AUTHOR]

In this paper, an active superconducting current controller is used for fault current limiting, protective coordination, and voltage compensating in a typical power system. In the grid-connected micro-grid, the performance of a conventional fault current limiter can disrupt the protective coordination of the micro-grid overcurrent relays as well as the relays between the main grid and micro-grid. The control strategy is designed for implementing normal limiting impedance in the upstream fault mode and a zero limiting impedance in the downstream fault mode so that the protective coordination between all relays is maintained. Also, to investigate the effect of the controller on voltage compensating, by obtaining the line transmission matrix, the controller setting parameters for compensating the voltage at any point of the line are obtained. In this case, the controller is adjusted such that the magnitude of the receiving end and the sending end voltages of the line become equal. Simulation results using MATLAB software confirm the proper performance of the proposed active controller for the above-mentioned purposes. [ABSTRACT FROM AUTHOR]

In this paper, a new method for both fault current limiting and voltage compensating using Active Superconducting Current Controller (ASCC) is proposed. The main objective of this paper is to present an appropriate control strategy for ASCC to achieve both the fault current limiting and voltage compensation purposes. Three different operating modes are defined for ASCC including normal mode, fault current limiting mode, and voltage compensation mode and a proper control strategy is designed for each mode. For the fault current limiting, the model of a typical three-phase system with ASCC is simulated and different states for current limiting in different levels are defined. Also, for the voltage compensating mode, the PI model for the line is considered and the line transmission matrix is obtained when the ASCC is connected at the sending end and middle of the line. Finally, proper settings for ASCC are determined such that the magnitude of the receiving end and the sending end voltages become equal. Simulation results using MATLAB software confirm the proper performance of the proposed method. [ABSTRACT FROM AUTHOR]

The open-phase fault in vector-controlled drives is known as one of the most prevalent failures that require immediate detection. It is still challenging to develop a trustable fault diagnosis scheme at light load, transients, and low-speed regions. This paper presents a novel open-phase fault diagnosis strategy for three-phase induction motor drives over the entire speed range and for different load conditions. By taking advantage of the second-order rotational park transformation (SORP), new fault indices are proposed to identify the open-phase location without using any additional sensors or electric equipment. Comparing with root-mean-square (RMS) calculation-based methods, the proposed method detects the fault at least twice faster, with minimal system resources. The presented scheme may be implemented simply and is robust against the operating point changes. Proof of the proposed fault detection and localization method has been shown through experimental tests on a 250-W three-phase induction machine which is controlled by TI-DSP F28335. [ABSTRACT FROM AUTHOR]

In this study, a dynamic state estimation (DSE) approach is proposed for power systems based on particle filter (PF) and ant colony optimisation for continuous domains (ACOR). Usually, the Kalman-based estimators with Gaussian noise assumption are utilised for DSE. However, this assumption is questionable for real power system data. Although PF methods offer a potential solution for this issue, the basic PF algorithm is time-consuming and suffers from sample impoverishment problem and degeneracy of the propagated samples. In this study, the search capability of ACORis utilised as an adaptive probability density function estimator to overcome these shortcomings and reduce the required particle numbers. The proposed approach minimises the computational effort by reducing the required particle numbers. The ninth-order model of the synchronous generator has been applied in this study. The performance of the proposed method is investigated through a two-area-four-machine test system as well as the IEEE 39-bus (New England) test system and it is compared with several advanced Kalman filter-based and PF-based approaches. The simulation results obtained for different case studies demonstrate the effectiveness and robustness of the proposed method against noises, abrupt state changes, and gross measurement errors. [ABSTRACT FROM AUTHOR]

Ground fault in the rotor winding of generators can cause serious damage to the generators and consequently, to the power plant. This paper proposes a practical online technique to determine the ground fault location in the rotor winding of a synchronous generator. The proposed technique is based on the analysis of the measured voltage and input/output currents of the rotor winding. The main distinguishing feature of the proposed technique is that, contrary to the existing technique, it is applicable to various types of excitation system. The accuracy and applicability of the proposed technique is demonstrated through both computer simulations and experimental tests. The experimental tests have been carried out using a new device which works based on the proposed technique. The results show that the proposed technique can determine ground fault locations with a higher accuracy compared with the existing techniques. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In the modern power systems operating at lower stability margins, conventional non-adaptive schemes cannot offer adequate protection for securing the power system, especially against combinational events. For major disturbances, the active power deficit is usually accompanied by reactive power deficit and frequency stability and voltage stability of the system are jeopardized simultaneously. In this paper, three adaptive combinational load shedding methods are proposed to improve operation of the conventional underfrequency load shedding scheme in order to enhance power system stability following severe disturbances. The proposed methods use locally measured frequency and voltage signals to counteract such events. In the proposed algorithms, load shedding is started from the locations which have higher voltage decay for longer period of time. The speed, location, and amount of load shedding are changed adaptively depending on the disturbance location, voltage status of the system, and the rate of frequency decline. Operation of the conventional and the proposed load shedding methods have been simulated in an actual large network. Obtained simulation results confirm that the proposed methods provide considerable enhancement in the power system voltage stability margin, and by using the proposed algorithms, various power system blackouts could be prevented. [ABSTRACT FROM AUTHOR]

The high penetration of Renewable Energy Sources into electric networks shows new perspectives for the network's management: among others, exploiting them as resources for network's security in emergency situations. The paper focuses on the frequency stability of a portion of the grid when it remains islanded following a major fault. It proposes an optimization algorithm that considers the frequency reaction of the relevant components and minimizes the total costs of their shedding. The algorithm predicts the final frequency of the island and the active power profiles of the remaining generators and demands. It is formulated as a Mixed-Integer Non-Linear Programming problem and the high computation time due to a large-size problem is mitigated through a simplified linear version of the model that filters the integer variables. The algorithm is designed to operate on-line and preventively compute the optimal shedding actions to be engaged when islanding occurs. The algorithm is validated for a typical distribution grid: the minimum amount of shedding actions is obtained while the most frequency reactive resources are maintained in operation to assure a feasible frequency. Finally, time-domain simulations show that the optimal solution corresponds to the one at the end of the network's transients following the islanding. [ABSTRACT FROM AUTHOR]

• This paper presents a new method to discriminate internal fault from other cinditions. • Important features are extracted using the Clark's transform and modified hyperbolic S-transform. • The proposed method shows desirable performance in the events accompanied by current transformer. • The proposed method is not affected by the noise. In this paper, a new method is proposed for discriminating internal faults from other abnormal conditions in power transformers such as inrush currents, external faults, over-excitation, and ultra-saturation. Since the differential current signals are non-stationary, a powerful tool such as S-transform is needed for their time-frequency analysis. In this study, some important characteristics are extracted using the Clark's transform and modified hyperbolic S-transform according to which different conditions are distinguished and classified. These features include energy contour of first level, variance index, standard deviation of second harmonic component, and a special criterion. In this paper, all possible transient conditions and the effects of the saturation of current transformers are considered. Various simulations for different operating conditions of transformer are performed via PSCAD/EMTDC software. Also, the entire process of modified hyperbolic S-transform and the proposed algorithm are done in MATLAB software. Simulation results show that the proposed algorithm can be reliably used for the identification and classification of different faults in transformers. [ABSTRACT FROM AUTHOR]