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This paper describes a new method of power-grid signal variation measurement, consisting of a demodulation algorithm and a set of measures (indices). The measures that will be presented are the abstract functionals, operating on the complex envelope of a signal. This paper presents a demodulation algorithm, definitions of proposed functionals, results of simulations, as well as laboratory experiments. [ABSTRACT FROM AUTHOR]

This paper presents a traveling-wave-based fault-location algorithm for hybrid multiterminal transmission systems that consist of one onshore overhead lines and multiple offshore submarine cables. Such hybrid transmission systems are common for interconnection of offshore wind farms to the main grid. The input to the algorithm is synchronized transient voltage measurements from all of the receiving ends. These measurements are obtained by optical voltage transducers equipped with global positioning system receivers for time synchronization. The discrete wavelet transformation is utilized to decompose the mode-1 voltages at the receiving ends. The first wave arrival times are then obtained by observing the squares of the wavelet transformation coefficient (WTC $^2$s). The transient simulations and the postfault analysis are carried out using EMTP-RV and MATLAB Wavelet Toolbox, respectively. The accuracy, limitations, and capabilities of the proposed algorithm are presented and discussed for different fault conditions. [ABSTRACT FROM AUTHOR]

This paper presents a transient-based algorithm for high-impedance fault identification on distribution networks. It uses the discrete wavelet transform to monitor high- and low-frequency voltage components at several points of the power system, being able to indicate the most likely area within which the disturbance has occurred, without requiring data synchronization nor the knowledge of feeder or load parameters. The proposed algorithm is evaluated through electromagnetic transients program simulations of high-impedance faults in a 13.8 kV system modeled from actual Brazilian distribution grid data. Solid faults, capacitor bank switching, and feeder energization are also simulated, considering the system with and without distributed generation. Obtained results show that the algorithm significantly reduces the search field of the high-impedance fault, reliably distinguishing it from other disturbances. [ABSTRACT FROM AUTHOR]

In substations with an inner bridge connection, the two main transformers are generally connected in parallel. The differential protection of the transformer, under normal operating conditions, may maloperate when the other transformer is switching on through the bridge breaker after scheduled maintenance. This paper analyzes the factors that may lead to the maloperation of transformer differential protection and concludes that local transient saturation of the current transformer (CT) caused by the decaying dc component in the magnetizing inrush is the main cause of the maloperation of the transformer differential protection. By detecting the time difference between the instant of sudden changes occurring in the transformer wye-side current and the instant of the differential current increasing, a new algorithm based on the time differential method is proposed in this paper, which can prevent the maloperation of transformer differential protection in substations with an inner bridge connection. On the basis of detailed analysis and simulation work, the new algorithm is verified to be applicable under the conditions of sympathetic inrush and CT saturation. [ABSTRACT FROM AUTHOR]

This paper introduces a new noniterative fault-location algorithm for long transmission lines compensated by a series flexible ac transmission systems (FACTS) device. In the proposed algorithm, synchronous voltage and current samples from both ends of the transmission line are used and the distributed parameter line model in the time domain is applied. Due to the difficulties in the modeling of the series FACTS devices during a fault, the presented method does not use the model of the series devices. In this paper, the fault-location problem is converted to an optimization one in which the location and resistance of the fault are the decision variables. The proposed method includes three stages. Two fault locations are obtained, corresponding to the first two stages. In stage three, the obtained results from stages 1 and 2 are compared, and the correct fault location is selected. The proposed algorithm is a noniterative one and it is suitable for transmission lines compensated by any series FACTS device which could have the overvoltage protection and can be in any operating mode. The performance of the proposed algorithm is evaluated under different structural and fault conditions. The simulation results confirm the accuracy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Multilevel current source converters are a smart choice for the high-power applications with low-voltage and high-current requirements. This paper presents the detailed analysis of a current source modular multilevel converter (CSMMC) and its application as a STATCOM. Various properties of CSMMC are compared with the voltage-source modular multilevel converter (VSMMC). The submodule inductance selection method and a sorting-based algorithm for inductor current balancing are proposed for CSMMC. The validity of the inductance selection method and the inductor current balancing algorithm are confirmed by the simulation of a three-phase CSMMC using PSCAD/EMTDC. The carrier phase-shifted sinusoidal pulsewidth modulation is used as the switching technique. The performance of a converter is analyzed with interleaved and noninterleaved carrier signals for the upper and lower arms. Results show that CSMMCs and corresponding VSMMCs have analogous features. Hence, the development on VSMMCs can be used for reference to CSMMCs and vice-versa. Furthermore, the control designs for CSMMC-based STATCOM are presented and verified using simulations. The obtained results of the proposed STATCOM show that the steady-state and transient performance of the system are quite satisfactory. This makes the CSMMC suitable for HVDC and flexible ac transmission systems applications. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel method for fault location in distribution networks using compressive sensing. During fault and prefault voltages are measured by smart meters along the feeders. The voltage sag vector and impedance matrix produce a current vector that is sparse enough with one nonzero element. This element corresponds to the bus at which a fault occurs. Due to the limited number of smart meters installed at primary feeders, our system equation is underdetermined. Therefore, the \ell ^1-norm minimization method is used to calculate the current vector. Primal-dual interior point (PDIP) and the log barrier algorithm (LBA) are utilized to solve the optimization problem with and without measurement noises, respectively. Our proposed method is implemented on a real 13.8-kV, 134-bus distribution network when single-phase, three-phase, double-phase, and double-phase-to-ground short circuits occur. Simulation results show the robustness of the proposed method in noisy environments and satisfactory performance for various faults with different resistances. [ABSTRACT FROM AUTHOR]

Part I of this two-part paper introduces a hardware-based mechanism to prevent/suppress the saturation phenomenon of the current transformer (CT). The mechanism includes an electronically switched resistor which is in series with the CT secondary winding. Part II performs a set of 1) offline digital time-domain simulation studies in the PSCAD/EMTDC environment and 2) control-hardware-in-the-loop (CHIL) test cases in a real-time digital simulation platform, to demonstrate technical feasibility of the proposed approach. The investigations also report the effect of CT saturation and the proposed desaturation mechanism on a digital distance relay. The digital algorithms of the relay and the control of the electronic switch are implemented in two NI-CRIO platforms for the CHIL studies. The investigation results demonstrate and verify the effectiveness of the proposed CT desaturation mechanism. [ABSTRACT FROM PUBLISHER]

This paper presents a new method for online symmetrical components and phase-angle extraction from high-voltage transmission-line faults. This method is based on the Adaline neural networks and the instantaneous power theory, also known as the p-q method. A new current decomposition is proposed in order to derive the direct, inverse, and homopolar current components. The average and oscillating terms of powers in the \alpha \beta frame are separated by using four Adaline neural networks. The Adalines use a cosine and sine as inputs in order to learn the linear combination of the powers. The resulting symmetrical components are used by three other Adalines for phase-angle estimation between direct and inverse current components. These phase angles permit classifying the fault types. The neural networks use an online learning process-based Widrow–Hoff algorithm and can adapt their weight parameters to the power-supply evolution. Simulation results show the performance and the robustness of this method and provide a perspective for protection relay improvement. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid algorithm for the ac/dc transmission expansion planning (TEP). The stochastic simulation method would consider random outages of generating units and ac/dc transmission lines as well as load forecast errors. The mixed-integer linear programming problem is decomposed into a master planning problem with integer investment decision variables and subproblems which examine the feasibility of master planning solution and calculate the optimal operation schedule over the planning horizon. The independent system operator would utilize the proposed method to select the optimal set of ac/dc transmission lines for satisfying TEP criteria: supplying load forecasts, minimizing investment costs, and optimizing market operations. The proposed set of dc transmission system may use either current source converters or voltage source converters. Numerical examples illustrate the effectiveness of the proposed TEP model. [ABSTRACT FROM AUTHOR]

In this paper, a new dc offset removal algorithm for real-time simulations is proposed. Physically transferred signals in a real-time simulation interface tend to contain a dc offset component for various reasons. This component decreases the accuracy and stability of real-time simulations. The dc offset tends to change according to circumstances which include changes in the system configuration and effects of the external environment which makes the static dc offset removal scheme inefficient. The proposed algorithm can estimate and remove a dc offset component dynamically from the input signal of the hardware under test. In the proposed algorithm, the optimal constant for the condition equation is calculated by using an iterative method and is used to estimate the frequency, time, magnitude, and dc offset component of the input signal. Four sampling points are used to calculate the optimal constant in each step. The proposed algorithm has relatively fast speed and good accuracy in comparison to conventional dc offset removal algorithms. In order to verify the performances of the proposed algorithm, offline and real-time dc offset estimation simulation tests were performed. The results of the simulation tests showed that the proposed algorithm can estimate the dc offset component promptly and exactly and can be applied to real-time simulations. [ABSTRACT FROM AUTHOR]

This paper presents a new two-terminal impedance-based fault-location algorithm, which takes into account the distributed parameter line model. The algorithm utilizes unsynchronized measurements of voltages and currents from two ends of a line and is formulated in terms of the fundamental frequency phasors of symmetrical components of the measured signals. First, an analytical synchronization of the unsynchronized measurements is performed with use of the determined synchronization operator. Then, the distance to fault is calculated as for the synchronized measurements. Simultaneous usage of two kinds of symmetrical components for determining the synchronization operator makes that the calculations are simple, noniterative, and at the same time highly accurate. The developed fault-location algorithm has been thoroughly tested using signals of Alternate Transients Program-Electromagnetic Transients Program versatile simulations of faults on a transmission line. The presented evaluation shows the validity of the developed fault-location algorithm and its high accuracy. [ABSTRACT FROM AUTHOR]

Real-time transient simulation of large transmission networks requires significant computational power. This paper proposes a field-programmable gate array (FPGA)-based real-time electromagnetic transient simulator. Taking advantage of the inherent parallel architecture, high density, and high clock speed, the real time Electromagnetic Transients Program (EMTP) is implemented on a single FPGA chip. It is based on a paralleled algorithm that is deeply pipelined, and uses a floating-point arithmetic calculation to achieve high accuracy for simulating fast electromagnetic transients. To validate the new simulator, a sample system with 15 transmission lines using full frequency-dependent modeling is simulated in real time. A timestep of 12 μs has been achieved based on a 12.5-ns clock period with high data throughput. The captured real-time oscilloscope results demonstrate excellent accuracy of the simulator in comparison to the offline simulation of the original system in the Alternative Transients Program version of EMTP. [ABSTRACT FROM AUTHOR]

This paper presents a novel morphological scheme for the identification of transformer magnetizing inrush. The scheme decomposes a current signal into multiresolution levels based on synthesis and analysis operators of mathematical morphology. It is able to discriminate between inrush and internal fault currents even in the case of an inrush with a low second harmonic component and an internal fault current with a high second harmonic component. Simulation studies have been undertaken to evaluate the scheme based on a three-phase high-voltage power transformer operating under different conditions, which is simulated with an Alternative Transients Program. The testing results show that the proposed scheme is able to identify inrush currents reliably and provides an alternative solution for transformer differential protection. [ABSTRACT FROM AUTHOR]

This paper deals with the postfault analysis of the operation of distance protective relays from the line terminals. The signals of the digital distance relays are processed in the offline regime with the aim of evaluating the particular relay operation case. First, the program enables imitating the fault-loop impedance measurements of the distance relays. Second, the two-end unsynchronized measurements of the relays are considered. The unknown synchronization angle is determined by using the developed noniterative procedure. Then, the distance to fault is calculated. It is applied for calculating the actual values of impedance for the line sections. Comparing the results of these two ways performs analysis of operation of the relays under resistive fault cases. The described postfault analysis algorithm has been tested with the fault data obtained from versatile Alternative Transients Program-Electromagnetic Transients Program simulations. The examples are reported and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a novel time-domain fault location algorithm for parallel transmission lines using two terminal currents. Parallel transmission lines with faults can be decoupled into the common component net and differential component net. Since the differential component net is only composed of the parallel lines and its terminal voltages equal zero, the proposed algorithm is based on the fact that the difference between voltage distributions, calculated from two terminal currents, is the smallest at fault point. To be practical, unsynchronized data and the transient transferring ability of the current transformer are taken into consideration. The algorithm needs a very short data window, and any segment of current data can be used to locate faults. The proposed algorithm is verified successfully using the simulation data generated by the frequency-dependent line model of the Alternative Transients Program and the field recording data provided by traveling-wave fault locators. Locating results show the satisfactory accuracy of the algorithm for various fault types, fault distances, and fault resistances. [ABSTRACT FROM AUTHOR]

This paper describes a solution for automated analysis of circuit breaker operation. The analysis is based on a record of waveforms taken from the circuit breaker control circuit by using a portable recorder and manually forcing an operation of the breaker. This solution was driven by a need to perform the analysis in a more timely and consistent manner than what is available with existing technology. The solution is implemented using advanced wavelet transforms for waveform feature extraction and an expert system for decision making. A web-based database solution for storing and retrieving both the field-recorded and processed data is also implemented. The software is developed in two versions: for field (substation) as well as off-line (office) applications. [ABSTRACT FROM AUTHOR]

A new research method is proposed for the medium-voltage (MV) vacuum circuit breaker's (CB's) mechanical condition monitoring, which combines the mechanism dynamic features simulation and mechanical condition recognition algorithm bised on artificial neural networks (ANNs). This method includes three steps: First, the relations between eigen- values and mechanical failures of a vacuum circuit breaker (CB) through simulation instead of measurement are obtained. In this paper, the mechanism dynamic features of a vacuum CB in failure are simulated; the simulation results indicate that the parameter that can be monitored-main angle-has different characters for different mechanism failures. Second, the eigenvalues for different failure conditions are described by three parameters. Third, mechanical condition recognition of the MV vacuum CB by an algorithm based on ANN is realized. It is concluded by the work mentioned above, both the known mechanical condition type and the new mechanical condition type of the medium-voltage vacuum CB can be recognized with predetermined reliability. [ABSTRACT FROM AUTHOR]

Frequency is an important parameter in power system monitoring, control, and protection. A least mean square (LMS) algorithm in complex form is presented in this paper to estimate power system frequency where the formulated structure is very simple. The three-phase voltages are converted to a complex form for processing by the proposed algorithm. To enhance the convergence characteristic of the complex form of the LMS algorithm, a variable adaptation step-size is incorporated. The performance of the new algorithm is studied through simulations at different situations of the power system. [ABSTRACT FROM AUTHOR]

This paper introduces advanced pattern recognition algorithm for classifying the transmission line faults, based on combined use of neural network and fuzzy logic. The approach utilizes self-organized, supervised Adaptive Resonance Theory (ART) neural network with fuzzy decision rule applied on neural network outputs to improve algorithm selectivity for a variety of real events not necessarily anticipated during training. Tuning of input signal preprocessing steps and enhanced supervised learning are implemented, and their influence on the algorithm classification capability is investigated. Simulation results show improved algorithm recognition capabilities when compared to a previous version of ART algorithm for each of the implemented scenarios. [ABSTRACT FROM AUTHOR]

Zone 3 of a distance relay is used to provide the remote backup protection in case of the failure of the primary protection. However, the risk of maloperation under stressed conditions such as heavy loading, voltage, and transient instability is quite high. Zone 3 is used in combination with the derivatives of the voltage and current, etc. to prevent maloperation. At times, the impedance characteristics that restrict the tripping area of relay are used to avoid maloperation due to load encroachment. This paper presents a novel zone 3 scheme based on combining the steady-state components (i.e., 60 Hz) and the transient components (TCs) using a state diagram that visualizes the sequence of studies that emanate from the sequence of events. The simulation results show that the novel zone 3 distance relay elements using the proposed method operate correctly for the various events. [ABSTRACT FROM AUTHOR]

In real time digital simulation of electromagnetic transients for equipment testing, solution output is provided at equidistantly spaced time points in order to synchronize the data exchange with external equipment. Switching events, which can occur in between these time points of solution output, are pinpointed by backward interpolation. To recuperate the time interval lost through interpolation, the simulation must be resynchronized with the real time clock. For this purpose, the use of a flexible time step size is desirable. However, in EM transients simulators based on nodal analysis techniques, time step size changes have so far involved changes of the nodal admittance matrix and, thus, imposed a large computational burden. This is avoided through the method flexible integration for readjustment in simulation of transients (FIRST), presented in this paper. Through this method, the characteristics of numerical integration are modulated such that time step size changes are achieved in a computationally very efficient manner and without modifying the nodal admittance matrix. [ABSTRACT FROM AUTHOR]