Search

A model expressing beams, pillars, and electrical wiring in a building for lightning surge simulation by circuit analysis method is proposed in this paper. The proposed model expresses the self‐surge impedance of the electrical wiring as a function of the distance between conductors and the radius of the electrical wiring. The mutual impedance is expressed by the distance between the surfaces of a structure and a nearby wire instead of the distance between the conductor centers. In the case of two conductors having far different radii in proximity, the distribution of electromagnetic fields around the two conductors is similar in horizontal and vertical arrangements. Thus, the electrical wiring nearby pillars can be treated as a horizontal conductor. The circuit analysis results show that the voltage difference generated between the structure and the electrical wiring is calculated more precisely by the proposed model than by the conventional model. [ABSTRACT FROM AUTHOR]

The increasing uncertainties in power systems have brought non-negligible influences on the dynamic behaviors. An accurate and efficient simulation method considering the effects of stochastic disturbances is of critical importance for the analysis of the dynamic performance of power systems. In this paper, a methodology for the simulation of stochastic transients in power systems is developed based on frequency shifting theory. The stochastic differential equations describing the stochastic process of parameter migration are represented through analytic signals. The frequency shifting operation is introduced. The Fourier spectra of analytic signals are shifted to reduce their maximum frequency contents, thereby permitting a larger time-step in time-domain simulation in accordance with Shannon's sampling theory. Through the trapezoidal Milstein scheme, the stochastic differential equations with shifted analytic signals are discretized. Branch companion models that process analytic signals for the simulation of stochastic transients are formulated. The numerical properties of branch models are further examined. The analysis of test cases demonstrates that the proposed method can be used to represent stochastic transients caused by parameter migrations accurately and efficiently. [ABSTRACT FROM AUTHOR]

The deployment of Li-ion batteries has been increasing extensively due to recent technological/economic breakthroughs and their high suitability to a range of applications. In this context, this paper (i) develops a simulation algorithm programmed in MATLAB® with a graphical user interface designed in Excel® to assess the transient responses in multiple Li-ion battery technologies and (ii) performs a comparative assessment of the transient responses to verify if there are significant differences. The simulation interface is required since the battery parameters are dependent on the state of charge; hence, conventional electromagnetic transients programs (e.g., ATPDraw®) cannot be directly applied to perform the simulations. Results demonstrate that the differences in the transient responses (terminal voltage) are considerable, particularly when applying robust input currents to the batteries (e.g., decreasing square wave and dynamic stress test). Among analyzed technologies, the Panasonic NCR18650B Li-ion battery showcased the most volatile transients. Hence, the results contradict the common sense that transients in Li-ion batteries are equivalent. The simulation interface is made available to foster further research on the topic. [ABSTRACT FROM AUTHOR]

The purpose of this article is to develop an improved new high voltage power supply model for magnetrons, used for the microwave generators in industrial applications. The design of this system is composed of new three-phase leakage flux transformer supplying by phase a cell, which multiples the voltage and stabilizes the current. Each cell in turn, supplies a single magnetron. An equivalent model of this transformer is developed taking into account the saturation phenomenon and the stabilization process of each magnetron. Each inductance of the model is characterized by a non linear relation between flux and current. This model was tested by EMTP software near the nominal state. The theoretical results were compared to experimental measurements with a good agreement. Relative to the current device, the new system provides gains of size, volume, cost of implementation and maintenance. [ABSTRACT FROM AUTHOR]

In order to ensure the safe and stable operation of high voltage direct current (HVDC) systems, this paper studies the lightning overvoltage at the neutral point of the HVDC converter transformer. The work first introduces the basic types of lightning overvoltage based on the CIGRE Benchmark 500 kV HVDC transmission system which is modeled in the electromagnetic transient program (EMTP) software. The high-frequency model of the HVDC transmission system is considered where lightning overvoltage at the converter transformer neutral point is studied at different values of the small reactance connected at neutral point grounding and different lightning strike locations. Although increasing the small reactance value can effectively suppress the lightning current, the lightning overvoltage will gradually increase. When the neutral point is grounded by 11 Ω small reactance, the lightning overvoltage is most serious, where the peak value can reach 415 kV. Also, the farther the lightning strike position from the converter transformer, the smaller the lightning overvoltage.

A derivation of the dynamic model of a medium voltage vacuum circuit breaker and induction motor in space vectors in coordinates α β 0 allow us to model switching transients in various dynamic states of the motor. In the case of the Clark transformation, the corresponding numerical integration technique can be selected including variable time-step integration techniques to avoid numerical instabilities due to the stiffness of the system. Assymetrical operations such as switching cause the power system to become unbalanced and the transformed equations α , β , and 0 are not uncoupled. Therefore, it is necessary to derive a coupling matrix between circuit breaker voltages and currents in the coordinate system α β 0 . The subject of our interest is switching overvoltages that arise when turning off small inductive currents by a vacuum circuit breaker. When deriving the model of a vacuum circuit breaker, all its properties encountered during this action are taken into account, i.e., current chop, virtual current chop, dielectric barrier in the circuit breaker and its recovery rate, and the ability of the vacuum circuit breaker to extinguish high frequency currents. Simulation results are compared with the measured results on a medium voltage motor as well as with the simulation results of the mathematical model of the test circuit according to IEC 62271-110 resolved using the nodal method (EMTP algorithm). Models are implemented in the MATLAB/Simulink programming environment. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is a recently developed converter architecture with the potential for high-voltage direct current (HVDC) transmission applications. Due to the large number of IGBTs and diode devices, modeling a modular multilevel converter (MMC) for electromagnetic transient type (EMT-type) simulations might be difficult. HVDC-MMC transmission system detailed models take a long time to compute. To solve this issue, simplified and averaged models have been suggested. In order to efficiently and accurately depict MMC-HVDC systems, several kinds of models are developed and compared in this study using EMTP-rv software. The results suggest that the kind of model to be used will rely on the study performed and the level of accuracy needed. [ABSTRACT FROM AUTHOR]

The smart inverter (SI) is an emerging technology, which enables the effective integration of distributed energy resources (DERs). Nevertheless, the operation by the only single SI function is not sufficient to deal with various conditions in a distribution system. In other words, all DERs are required to rapidly update the proper mode of SI functions depending on the system conditions. In this article, we propose the new active distribution management system (ADMS) for photovoltaic (PV)/energy storage system (ESS) integrated system based on the SI functions. It effectively regulates the system voltage, and it solves the line congestion problem in a distribution system by adaptively controlling the mode of SI functions. This method enables DER to effectively regulate its generation without the additional controllers. The effectiveness of the proposed ADMS is verified by several case studies on a practical distribution system in South Korea with the real measurements of generation from PV and load consumption based on the electromagnetic transient program. Also, the PV/ESS integrated system prototype of 100 kW is implemented for the experimental verification of the proposed ADMS. [ABSTRACT FROM AUTHOR]

• Lightning current waveform effects on critical flashover currents are assessed. • Negative and positive first return-stroke current waveforms are considered. • Typical 150 kV and 400 kV double-circuit overhead lines are evaluated. • Statistical distributions of the CIGRE current waveform parameters are considered. • Impact of positive lightning strike parameters is more marked for backflashovers. This paper investigates the influence of the CIGRE lightning current waveform parameters on the computation of fast-front overvoltages and critical lightning currents causing flashover of overhead transmission line insulation. The investigation is conducted via ATP-EMTP simulations employing both negative and positive lightning current waveforms corresponding to first return strokes. Typical 150 kV and 400 kV double-circuit overhead lines are evaluated by performing shielding failure and backflashover simulations. The statistical distributions of the parameters required as input for the CIGRE lightning current waveform (front time, maximum steepness, time to half value) are considered in simulations to quantify and analyze their effects; this enables the comparison between negative and positive lightning strikes. The waveform parameters do not affect considerably the critical shielding failure flashover current for both polarities; the most influential parameter in this case is the time to half value. On the other hand, the wavetail duration influences the least the critical backflashover current; the latter is lower for waveforms with faster wavefront (lower front time and higher maximum steepness). The impact of the waveform parameters of positive lightning strikes is more marked for the backflashover case due to their larger variations compared with negative strikes. [ABSTRACT FROM AUTHOR]

• Tower and insulator models validated through comparisons with experimental results. • Systematic evaluation of the effects of several parameters on the MV circuit voltages. • Critical currents calculated for different combinations of soil resistivity and ground impedance. • Subsequent strokes are unlikely to cause backflashovers in the HV and MV circuits. • HV and MV circuits are shown to have excellent lightning performances. This paper presents an analysis of the overvoltages caused by direct lightning strokes to a hybrid overhead line with 138 kV, 13.8 kV, and 220 V circuits. The primary focus is on medium voltage line overvoltages and their dependence on key parameters, including ground impedance, soil resistivity, stroke current front time, conductor characteristics, lightning channel impedance, insulator capacitance, conductors' sags, and tower surge impedance. Using specific models for the transmission tower and high-voltage insulators, validated through laboratory tests and EMTP simulations, critical currents are determined for varying soil resistivity and impulse impedances. The analysis confirms the line robust performance against stroke-induced backflashovers. [ABSTRACT FROM AUTHOR]

Soil ionization, that is, electrical discharges developing in the ground, may have a significant impact on the behavior of grounding systems under lightning currents, as it causes a reduction of the impulse ground impedance. This may have several implications on insulation coordination studies for power systems. The effects of soil ionization have not been completely clarified yet due to its complexity associated with soil characteristics and conditions, ground electrode configuration, lightning current characteristics, as well as difficulties in the accurate determination of discharge activity. This study deals with the experimental investigation of the lightning impulse behavior of wet sandy soil. An experimental setup and measurement procedure are introduced for this purpose. Experiments under lightning impulse voltages of negative polarity were performed on two wet sandy soils, both as obtained from their extraction sites, as well as after drying and manual addition of moisture; thus, the influence of the soil sample preparation procedure is evaluated. Results are discussed considering soil ionization inception, electrical breakdown of soil, impulse impedance, and soil electrical properties. A simulation model is proposed for the prediction of the instantaneous impulse impedance when soil ionization occurs; this model is suitable for time domain simulations in ElectroMagnetic Transients Program (EMTP)-type software. [ABSTRACT FROM AUTHOR]

This article presents a detection technique for data manipulation attacks in distribution systems using transient information present in the measurements. This technique is based on the fact that any legitimate changes in the system will have a transient response which can be measured by the monitoring system. An algorithm is developed for obtaining the transient solution for three-phase distribution networks. A backward–forward sweep technique is developed for the proposed radial electromagnetic transient program (EMTP) which exploits the radial structure of distribution network. An inclusive transient model compatible with the proposed three-phase radial EMTP for three-phase synchronous generators is also developed. The proposed radial EMTP has been benchmarked with conventional EMTP with 5-bus and 22-bus radial distribution systems and with the same test systems, the proposed detection functionality is evaluated. It is shown that the transient solution provided by radial EMTP are in agreement with the results of conventional EMTP. It is also demonstrated that the deviations between the measured values and the solution of the radial EMTP increase significantly during the transient period when a data manipulation attack is carried out. [ABSTRACT FROM AUTHOR]

• VFTOs in GIS substations are dangerous and can damage the internal insulation of substation equipment. • VFTO reduction methods should be effective at all GIS substation points and have no limitations. • Providing a combined solution can increase VFTO reduction and increase VFTO reduction up to 60 %. • Using the real GIS substation of Arak city for simulation increases the validity of the results. The use of gas-insulated substations in high voltage levels of power systems is expanding due to its many advantages, such as the need for less space, resistance to environmental pollution, high reliability, and no need for continuous maintenance. One of the phenomena that threatens the insulation distances inside the closed enclosure in these substations is very fast transient voltages. These overvoltages are dangerous for the equipment inside the substation and connected to it as a result of the switching operation of gas-insulated substations, and if repeated, it can damage the internal insulation of the equipment. Also, these transient overvoltages in special cases such as extremely high voltages may cause serious damage to expensive substation equipment. Therefore, in this article, while examining the existing methods to limit very fast transient overvoltages in different and sensitive points of GIS substations, a new combined method based on the simultaneous use of nanocrystalline rings in the busbar and two XLPE cable paths, The direction of connecting the power transformer to the substation is provided. The results of the simulation on the 230 kV side of the GIS substation of Arak city show that the method proposed in this article has the lowest range of overvoltages compared to other methods. By using the proposed combined method, the range of very fast transient overvoltages in the power transformer terminal of the network under study is reduced by 60 % and this reduction can be seen in other points of the substation as well. [ABSTRACT FROM AUTHOR]

A generalized formulation of earth-return impedance and admittance for overhead lines above a multi-layer earth is derived. An equivalent homogeneous earth method (EHEM) and a Method of Moments - Surface Admittance Operator (MoM-SO) method with modified earth-return Green function considering an N-layer earth are also proposed. The frequency responses of wave propagation characteristics are evaluated by the newly proposed formulas and compared to those found from existing formulas in software used for the simulation of electromagnetic transients. Transient simulations performed in an electromagnetic transient (EMT) type simulation tool are also presented. It is shown that the proposed generalized formulas, the EHEM and the modified MoM-SO method, are in agreement, validating and verifying the results found in this paper. [ABSTRACT FROM AUTHOR]

This paper discusses the back-flashover (BFO) phenomena in a high-voltage (HV) vertical double-circuit transmission line by means of numerical simulations. The single- and multiphase BFOs are analyzed considering 24 cases of AC-voltage angles and nonlinear characteristic of flashovers, taking advantage of the circuit analysis method in time domain. The models used in circuit analysis are the TEM-delay model, which can take into account the non-TEM characteristics of tower and line, and the conventional models. Prior to the BFO analysis, the characteristics of circuit models are compared and discussed with the numerical electromagnetic analysis results. In BFO analysis, it is clarified that the occurrence probability of the multiphase BFO is heavily depending on the bias AC-voltages. The relation of measured BFO phases and AC-voltages are well explained by the TEM-delay model with the valid lightning current magnitude. The conventional circuit models could have underestimated the occurrence of BFOs in HV transmission lines. The analysis and discussions shown in this paper can be utilized for advanced evaluation of lightning performance of transmission lines that considers the seriousness of lightning accidents. [ABSTRACT FROM AUTHOR]

This paper deals with the protection against earth faults in medium voltage meshed networks with unearthed neutral. A communication-supported protection system is proposed and assessed through numerical simulations. The protection system is based on the use of directional relays installed at both ends of each line of the network. Each relay communicates by sending permissive signals following the so-called directional comparison overreaching transfer trip scheme. Each directional relay implements a new transient fault detection algorithm based on the angle between the zero-sequence voltage and current phasors. The phasors are estimated at the dominant frequency of the network transient-response within the first milliseconds after the fault, which range can be evaluated by means of a simplified circuit equivalent representation. The performances of the protection system and the detection algorithm are evaluated for different network configurations. By using a specifically developed co-simulation tool that interfaces EMTP-RV with Matlab, the influence of the communication latency is also analyzed. A Monte Carlo method is applied to analyze the effects of fault resistance, incidence angle and fault location variations. Results of a real-time simulation obtained in the Opal-RT environment further support the applicability of the algorithm. [ABSTRACT FROM AUTHOR]

En este artículo se describe el desarrollo de una metodología para simular la dinámica de una red de energía eléctrica a través del procesamiento paralelo. Los sistemas eléctricos se modelan mediante ecuaciones diferenciales, por lo que es necesaria la implementación de métodos numéricos para encontrar la solución de dichas ecuaciones. La metodología consiste en la división de una red eléctrica en subredes que están desacopladas en tiempo entre sí, es decir, las subredes resultantes se encuentran conectadas entre sí mediante líneas de transmisión. El tiempo de viaje a través de las líneas produce el desacoplamiento en tiempo necesario para que la solución de las ecuaciones diferenciales pertenecientes a cada una de las subredes se pueda obtener en paralelo. El caso de estudio principal es una red eléctrica sencilla y para su simulación con Matlab se utiliza de la librería de procesamiento paralelo. Los resultados obtenidos con la técnica de procesamiento paralelo se comparan con la simulación secuencial también implementada en Matlab y con el ATP (del inglés Alternative Transient Program) para validar los resultados obtenidos.

This paper describes the background of Electromagnetic Transients Program (EMTP) and reviews original EMTP development at Bonneville Power Administration of the US Department of Energy starting from 1966 to 1984. Then, the paper briefly explains the development and present situation of four EMTPs, that is, ATP‐EMTP, EMTP‐RV (now EMTP®), EMTDC/PSCAD and XTAP. In addition, the line/cable parameters and the modeling methods prepared in EMTPs are described, and related problems are explained. Finally, the recent trend and future of electromagnetic transient simulations are discussed. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This letter devises a quantum electromagnetic transients program (QEMTP) which is the first attempt to tackle the computational challenges in solving EMTP through quantum computing. The main contributions lie in: (1) A quantum-enabled EMTP formulation with Dommel's model encoded in quantum states; 2) An Harrow-Hassidim-Lloyd (HHL)-based QEMTP to solve the discrete-time nodal equations; 3) An iteration-based HHL revision for mitigating temporal errors to achieve high accuracy of QEMTP with limited quantum resources. Case studies verify the correctness and efficacy of QEMTP in simulating both fast and slow dynamics. [ABSTRACT FROM AUTHOR]

Assessing the transient behavior of electric power transmission/distribution systems, when they are subjected to major disturbances such as lightning discharges, is an essential procedure to ensure the operational security of these systems, in order to supply good quality power to all consumers. Electromagnetic transient studies are routinely performed in the planning and operation phases of these systems, by using world widely known computer programs, among which stands out the Alternative Transient Program (ATP), via its graphical interface ATPDraw. However, preparing files for running case studies by using ATPDraw can become a time-consuming and human error-prone task. To overcome this drawback, this paper presents a toolbox for automatic generation and execution of Alternative Transient Program input files based on information directly obtained from technical databases of distribution utilities. This toolbox aims to reduce modeling time and susceptibility to human errors in the process of describing the grid in the software input file, which constitute the biggest obstacles to the extensive use of this program in real electric transmission/distribution networks. For the toolbox validation, a comparison was made between the input file generated by the ATPDraw auxiliary graphic interface and the file generated by the proposed toolbox by using the IEEE 13-bus and IEEE 34-bus test feeders. Besides that, the simulation results of both feeders for both softwares were compared, so that the correct operation of the Alternative Transient Program automatic case creator and executor proposed in this article were proved. In addition, the automatic generation of ATP cases for larger grids is exemplified with the IEEE 123-bus test feeder.

This paper proposes a systematic approach to simulating stochastic electromagnetic transients in emtp, through the reliable numerical solution of stochastic differential equations. Actually, numerical integration schemes for stochastic differential equations (sdes) are not available in emtp. It is shown how to set up the Semi-Implicit Backward Euler scheme specific for stochastic differential equations. The implemented interaction strategy between the engine for the solution of electrical circuits and the engine for the Transient Analysis of Control Systems of emtp is exploited. This is a bolt from the blue feature of this simulator that makes it the only one on the shelf able to handle stochastic differential equations. Exploiting this unveiled capability, some basic and tutorial case studies are presented. They pave the way for the simulation of more complex circuits and systems that go beyond the scope of this work. Simulation files are provided as supplementary material and they are available on GitHub. [ABSTRACT FROM AUTHOR]

The minimum backflashover current, IBF, of typical overhead transmission lines is estimated through ATP-EMTP simulations considering the tower ground resistance and AC voltage phase angle as parameters. Several single- and double-circuit lines are investigated with operating voltage from 66 kV to 765 kV and Basic Insulation Level from 325 kV to 1950 kV. The backflashover rate, BFR, of the investigated lines is obtained using an expression that accurately considers lightning incidence to the line for prospective currents higher than IBF; the relevant CIGRE expression underestimates BFR. BFR can be easily estimated using solely the phase angle values corresponding to zero AC voltage of the phase conductors. Based on the IBF and BFR results, simple expressions are introduced for the calculation of an equivalent minimum backflashover current as a function of insulator length and tower ground resistance or impulse impedance. These expressions enable straightforward estimation of BFR without the need for time-consuming simulations or laborious analytical methods adopting simplifying assumptions. [ABSTRACT FROM AUTHOR]

This paper presents an equivalent time-domain grid-following inverter-based generator model, which can be used in Electromagnetic Transients Programs (EMTP). It is developed in the Alternative Transients Program (ATP) using the ATPDraw graphical interface. A complete benchmark photovoltaic model available in ATP/ATPDraw environment is taken as reference to evaluate the proposed model under steady-state and fault scenarios. The obtained results showed that the proposed model is simpler and less time-consuming than the complete model, being capable of easily consider the implementation of different components/controls of Inverter-Based Resources (IBR) in EMTP. The settings used in the implemented control schemes proved to be effective, resulting in an average error of about 2.33% during fault conditions. Also, a reduction of about 70 % in the execution time was achieved when compared to the analyzed benchmark one, attesting its usefulness for power system studies with high presence of grid-following IBRs. • Existing models are not trivial to change operation points and control strategies. • Software implementation detail are often left in second plane in the literature. • Simulations are 70 % faster when compared with complete switched models. • Easily adaptable to be applied with different implementations of IBR components. • Accurate even during faults (average error of 2.33 % in the injected apparent power). [ABSTRACT FROM AUTHOR]

Nowdays, regarding to the great us of sensitive devices, the quality of the transmitted power, have become an important issue. One of the most important dimension of power quality is magnitude load terminal voltage. Different devices has been designed for voltage sag compensation or other distortions. UPQC is a compensator which is able to compensate all distortions, such as voltage sag, flicker, unbalance, harmonic and current distortions such as reactive, harmonic and unbalance. Several controllers have been designed to compensate the whole or a part of distortions. In this paper its going to introduce a kind of controller which is able to compensate voltage sag to direct and simple by UPQC. At the end, simulation and voltage sag mitigation is going to be performed by ATP-EMTP software.

The fault classification of medium-voltage transmission lines consisting of wind farms connected to the high-voltage (HV) transmission networks is carried out using the power-spectrum-based hyperbolic S-transform (HST) powerful technique for analysing non-linear and non-stationary fault signals through the non-intrusive monitoring systems. The HST technique extracts the useful features in the time-frequency domain from measuring fault current waveforms of the HV utility side to discriminate the fault types. Parseval's theorem is applied to each HST coefficient to quantify the energy distribution of various fault types for reducing the size of inputs for recognition algorithms. Next, multiclass support vector machines achieve identification. The results have proved that the proposed classification technique is independent of fault resistance, source impedance, and fault inception angles. Extensive simulations are conducted using the electromagnetic transients program to show that the recognition accuracy of the fault classification for all types is up to 96.84%. [ABSTRACT FROM AUTHOR]

The characteristic impedance of a transmission line, a wire or a conductor changes in a non‐uniform manner if the distance to the ground at all points longitudinally is not the same. Vertical conductors, transmission towers and sagging overhead lines are examples for the non‐uniform lines. In this study, lumped‐parameter‐based state variable representation of the single‐phase non‐uniform line is described. From the lumped‐parameter non‐uniform line model a linear set of first‐order differential equations is obtained in the form of state equations and this analytical expression is solved in closed form using MATLAB to obtain the transient response directly in the time domain. The closed‐form solution has the advantage of obtaining the response of the system at an instant without the need for data in the previous states except for the initial conditions. The method also allows attaining the voltage and current profile of the system for any instant. In the illustrative cases presented, the systems with different surge impedance variations are considered and the surge response of a vertical conductor, an exponential line, and a horizontal cone and a vertical cone with constant and also varying propagation velocity are computed. The results are verified by those obtained using s‐domain simulations of distributed‐parameter transmission line and inverse Laplace transform. [ABSTRACT FROM AUTHOR]

As a new highly penetrated power source of modern power systems, doubly fed induction generator (DFIG)‐based wind turbine (WT) has a different fault current contribution when compared with a synchronous generator. DFIG‐based WT's fault current has significant impacts on distance relay's performances and may result in maloperation. In this study, the impacts of DFIG‐based WT's fault current on the dynamic performances of two typical distance protection elements, mho and polarisation, are studied in terms of EMTP simulations and fault current expressions in symmetrical fault scenarios. It is discovered that the zone‐1 distance relays of the lines connecting to DFIG‐based wind power plants tend to overreach. Also, the following analysis indicates that the transient components of DFIG‐based WT's fault current and the phasor estimation unit are the underlying reasons. With those understanding, this study is expected to help design new setting methods and for distance protection in power systems integrating wind power plants to prevent this kind of possible overreach. [ABSTRACT FROM AUTHOR]

The modular multi‐level converter based direct current (MMC‐DC) power system is a dynamic equilibrium system, and the control of MMC is quite important to realise instantaneous balance of active and reactive power. Until now, the control architecture with outer‐loop, inner‐loop and circulating current controllers is widely used for MMCs in the DC power system, and these controllers are required to have excellent dynamic response and robustness. However, controllers based on existing proportional–integral (PI) control or conventional sliding‐mode control (SMC) have unsatisfactory performances. Therefore, an improved SMC method is proposed in this study for inner‐loop and circulating current controllers. Compared with PI and conventional SMC, the improved SMC has better dynamic response and robustness performance and can suppress chattering phenomenon substantially. The simulation model of a four‐terminal MMC‐DC system is established in power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC), based on which, comparison between PI control, conventional SMC and the improved SMC under typical working conditions, e.g. steady state, large disturbances of power step, is conducted, and the feasibility and superiorities of the improved SMC are verified. [ABSTRACT FROM AUTHOR]

The electromagnetic fields, which are produced by lightning currents flowing into a transmission tower and into overhead ground wires, spherically expand with time, and propagate as non-transverse electromagnetic (TEM) waves at least within the round trip time of the traveling wave along the tower. In this paper, a distributed-parameter line model of a vertical double-circuit transmission tower with an overhead line struck by lightning is composed considering the non-TEM characteristics. The surge impedances of the tower, ground wires, and phase conductors increase with time and reach their TEM-mode or steady state values with time constants determined from the configuration. In addition, the significant wave attenuation along the tower is included in the circuit model according to the propagation characteristic determined by the tower configuration. The virtual inductive grounding impedance or damping circuits for approximately representing the wave attenuation is no longer needed. The proposed model is applied to four types of transmission towers. Waveforms of voltages across insulator strings computed by the finite-difference time-domain method, which are regarded as the reference, are well reproduced by the proposed model. Computation efficiency is drastically improved by the proposed model comparing to the numerical electromagnetic field analysis. [ABSTRACT FROM AUTHOR]

This study presents a novel multi-rate algorithm for the co-simulation of power system transients using base-frequency dynamic phasor solver for frequency adaptive simulation of transient (BFAST) and electromagnetic transient (EMT) solvers. The BFAST solver alters its solution technique from dynamic phasors to EMT based upon the frequency contents of the waveforms being simulated. A changeover algorithm between the two solvers is also presented. The BFAST solver is then integrated with an industrial-grade EMT solver to develop a BFAST–EMT multi-rate co-simulator. The interface between the two solvers is established using transmission lines at the partitioning locations. The co-simulator combines the benefits of dynamic phasors, frequency adaptive simulation of transients, parallel processing, and multi-rate simulation. The study describes the several solution modes of the proposed co-simulator. Illustrative examples are included to demonstrate the accuracy and computational benefits of the proposed co-simulator. [ABSTRACT FROM AUTHOR]

This study proposes an alternative method to calculate the transient responses of multi‐conductor overhead transmission lines based on ABCD representation, recursive convolutions and numerical method for rational approximation in the frequency‐dependent curves. In the classical universal line model, the characteristic admittance matrix Yc(ω) and propagation matrix H(ω) are represented by rational functions. In H(ω), previous and correct identification of the modal travelling times is required. However, these modal travelling times are estimated numerically, which do not offer good accuracy in some cases. This fact has a considerable effect on the rational representation of H(ω) itself and consequently on the transient responses. In the alternative method, a previous estimation of the modal travel times is unnecessary because when using the ABCD representation for each propagation mode, a direct relation exists between the currents and tensions of the receiving and sending ends. These relationships are fitted by smooth rational functions, and then, using recursive convolution methods, the authors obtain the explicit equations of the currents and voltages to calculate the transient responses. The results demonstrate that the alternative method is accurate when compared with the frequency‐domain solution of the transmission line transformed to the time domain using the numeric Laplace transform and with the Bergeron method. [ABSTRACT FROM AUTHOR]

To evaluate and improve the performances of control and protection strategies for large‐scale AC grids, simulation models that can adopt a much larger time‐step, provide instantaneous and wide frequency‐band phasor values simultaneously are desirable. However, the traditional electromagnetic transient (EMT) model is numerically expensive and the transient stability (TS) model only preserves low‐frequency dynamics. To resolve these issues, the shifted frequency phasor (SFP) modelling is generalised based on specific matrix transformations and SFP models of typical components in large‐scale AC grids are derived hereafter. Unlike traditional models, the SFP models can produce instantaneous and wide frequency‐band phasor waveforms simultaneously, while the latter matches the envelopes of the former exactly. Moreover, the simulation efficiency is dramatically improved by adopting a much larger time‐step. The performance concerning the accuracy and efficiency is compared with the traditional EMT and TS models by simulating a practical large‐scale AC grid under different scenarios. [ABSTRACT FROM AUTHOR]

This study investigates the mitigation of transient overvoltages (TOVs) in a microgrid supplied by renewable distributed generation resources, which include photovoltaic (PV) generators, hydro generation unit, and wind power generators. ATP/EMTP is used in this study as electromagnetic transient software. Accurate simulation models are needed to carry out the study. Therefore, a three‐phase PV system model based on the equivalent Newton–Raphson circuit is used, and the efficiency of the PV system components is studied. Then, the use of the PV generation system model for switching studies is investigated using two different electrical systems. The use of different mitigation methods for TOVs at the microgrid is investigated. Three different mitigation methods are considered. First, a device to compensate reactive power such as static var compensator (SVC) is represented as a TOVs mitigation method. Then, adding a supercapacitor as TOVs mitigation method is evaluated. After that, a combination of active and reactive power simultaneously to mitigate TOV, by the addition of SVC to a supercapacitor, is investigated. The grid‐connected mode and isolated mode of the microgrid are considered. The results show that the usage of SVC with supercapacitor has the ability to mitigate the transient overvoltage and the waveforms are more regular. [ABSTRACT FROM AUTHOR]

Service unavailability of transmission lines, particularly in mountain areas due to the direct and indirect lightning strikes, is considered as a challenging issue within electric companies. Therefore, the efforts to mitigate the power outages caused by this phenomenon have been introduced. In this study, an attempt has been made to study the different types of externally gapped line arresters (EGLAs) considering the Pinceti model and discharge voltage curve. Based on the best selected EGLA, the installation effect of EGLA on the possibility of instance back‐flashover in different phases of the transmission line is investigated in the presence of downstream shield wire. For assessment, a double‐circuit 400 kV transmission line in a mountainous area is modelled in EMTP‐RV software. Then, an extensive analysis is carried out to verify the effectiveness of this method. The obtained results show the acceptable transmission line direct lightning protection can be achieved by four EGLAs in upper and middle phases with downstream shield wire. Although employing the downstream shield wires in the transmission line imposes more costs, but by using them, the scale and capability of EGLAs can be reduced. [ABSTRACT FROM AUTHOR]

Gas and oil pipelines are widely used to supply customers. They are often laid in parallel with high voltage power lines, sharing right of way. When the pipeline is located near overhead high-voltage power, corrosion caused by induced voltages from AC power lines can occur in utility pipelines. Therefore, the calculation of induced voltage is always required for both interference and maintenance workers as well as pipeline facility safety. For parallel distribution lines, the calculation method for the induced voltage is not suitable due to the excessive error caused by using the screening factors of the neutral current. For a more practical analysis of the induced voltage, a new analysis is needed using the actual neutral current and which also considers the overhead ground conductor and the neutral conductor. This paper analyzed the induced voltage from a parallel distribution system using Carson’s formula and vector analysis. Simulation analysis results are verified by separate Electromagnetic Transient Program (EMTP) simulation.

A triazole heterocyclic compound namely 3-(4-ethyl-5-mercapto-1, 2, 4-triazol-3-yl)-1-phenylpropanone (EMTP) was examined for its corrosion protection of mild steel (MS) against 1 M hydrochloric acid medium using gravimetric techniques. EMTP exhibited excellent corrosion protection performance at low and high concentrations towards MS in HCl solution. Comparison of corrosion protection performance of EMTP and its parent triazole and temperature effects of on inhibition efficacy were also studied. EMTP has potential corrosion inhibitor for mild steel in 1.0 M hydrochloric acid solution with the highest protection efficacy of 97% at 303 K. The weight loss findings implied that EMTP protects the metal surface corrosion through the creation of a protective layer at the surface mild steel–corrosive solution interface. The inhibitive efficacy increases with the increase of inhibitor concentration and decreases with increased temperature. The adsorption of EMTP on the surface of MS follows Langmuir’s adsorption isotherm process. DFT method was conducted on EMTP molecule to calculate the quantum chemical parameters and to determine the relationship between the molecular structure of EMTP and protection performance. The molecular parameters, such as energy gap and frontier molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), and the absolute electronegativity (χ) value from inhibitor molecules to unoccupied d-orbital of iron atoms on the mild steel surface were also determined and correlated with protection efficiency. The theoretical findings revealed that the protection performance of EMTP increased with the increase in HOMO energy, and the nitrogen, oxygen and sulfur atoms are most probable positions for bonding through giving electrons to the d-orbital of iron atoms on the mild steel surface.

Short circuit fault occurrence in high-voltage DC (HVDC) systems causes extremely high currents in a fast raising time that does not experience current zero-crossing. To protect HVDC systems/grids against fault current, fast HVDC breaker is an essential equipment. This study presents the design procedure of a novel HVDC breaker based on solid-state controllable reactor which is able to reduce the fault current's rate of rise and fault current amplitude to less than grid nominal current in the breaking process. The main achievement of the proposed HVDC breaker is that not only breaker does not encounter fault current, but also none of the series HVDC equipment is influenced by the fault. The designed breaker performance is studied by PSCAD/EMTPS, and then the simulation results are validated by the developed laboratory experimental setup.

This study presents a novel multi-rate algorithm for the co-simulation of power system transients using base-frequency dynamic phasor solver for frequency adaptive simulation of transient (BFAST) and electromagnetic transient (EMT) solvers. The BFAST solver alters its solution technique from dynamic phasors to EMT based upon the frequency contents of the waveforms being simulated. A changeover algorithm between the two solvers is also presented. The BFAST solver is then integrated with an industrial-grade EMT solver to develop a BFAST–EMT multi-rate co-simulator. The interface between the two solvers is established using transmission lines at the partitioning locations. The co-simulator combines the benefits of dynamic phasors, frequency adaptive simulation of transients, parallel processing, and multi-rate simulation. The study describes the several solution modes of the proposed co-simulator. Illustrative examples are included to demonstrate the accuracy and computational benefits of the proposed co-simulator.

Here, using the probabilistic evaluation based on the Monte Carlo method, back-flashover rate and shielding failure flashover rate of 230 kV overhead transmission lines in the western regions of Iran are evaluated. To such an aim, first, the number of thunderstorm days per year is collected from the reported weather information in order to determine the ground flash density. Then, using MRU-200 equipment, the tower-footing resistance of several towers is measured. Matlab® software is used in order to produce lightning surges considering its probabilistic nature and randomly distribution on the ground to evaluate striking distance based on the geometric model. Then, calculated parameters are transferred to EMTP-RV software by establishing a link to perform the transient simulation and report the results for modelled 230 kV transmission line. Finally, considering IEEE-1243 standard, it is shown that due to high ground flash density, using 230 kV tower with one shield wire is not sufficient to protect the line against lightning phenomena.

Electromagnetic transients (EMT) simulation is the most accurate and intensive computation for power systems. Past research has shown the potential of accelerating such simulations using graphics processing units (GPUs). In this paper, an efficient GPU-based parallel EMT simulator is designed. Threadoriented model transformations are first proposed for the electrical and control systems. Following the transformations, the electrical system is represented by connected networks of massive primitive electrical elements, the computations of which can be constructed as massive fused multiply-add operations and solutions to a linear equation. The control systems are represented by a layered directed acyclic graph with primitive control elements that can be dealt with using single-instruction-multiple-threads groups. Finally, code automation tools are designed to form the GPU kernels. Compared with past work, the proposed model transformations improve the degree of parallelism. Most importantly, the code automation tools improve computational efficiency by substantially reducing addressing and memory access, and render the implementation of the algorithm more general and convenient. Test systems of different sizes were created by connecting multiple IEEE 33-bus distribution systems and adding distributed generators. Simulations were performed on NVIDIA's K20x and P100 cards. The results indicate that the proposed method significantly accelerates EMT simulations compared with a CPU-based program. Real-time performance was also achieved under certain conditions.

Utilizing double-circuit lines may represent a challenge for distance relaying functions owing to the significant impacts of the mutual coupling among the adjacent conductors. This paper proposes a new adaptive distance relaying scheme for double-circuit transmission lines using fuzzy logic tuning. The scheme depends on two basic steps. First, the impacts of the mutual coupling of the adjacent conductors on the accuracy of the distance relaying core are minimized based on the decoupling feature of modal transformation. Then, a dedicated online intelligent tuning mechanism is utilized to precisely improve the relay reach. The adaptive neuro-fuzzy inference system is employed to realize an optimum design of the aimed tuning mechanism. A thorough investigation of the proposed scheme is performed utilizing a detailed modeling of a typical 400-kV interconnection system with both single- and double-circuit line segments. The electromagnetic transient program (ATP-EMTP) is employed for modeling the considered power system, whereas the protection scheme is constructed and tested using MATLAB. Finally, the performance of the proposed relaying scheme is investigated under different load conditions, various fault types and fault locations to visualize its efficacy precisely. As compared with conventional distance relaying core, the proposed adaptive distance scheme has a precise fault distance estimation with a reach error less than 6% of the total line length. Accordingly, a corrected declaration of the faulted zone is realized along the entire range of the protected line despite the added fault resistance, loading condition and fault type. [ABSTRACT FROM AUTHOR]

As more than 80% of single line to ground faults in power transmission lines (PTLs) are transient, single pole auto‐reclosure (SPAR) is of considerable importance for increasing the successful SPAR rate, improving power system stability and reducing shocks to the power systems. In this study, a new two‐step strategy for ASPAR is presented. In the first step, the fault type (permanent or transient) is determined using the derivative of the first harmonic of the faulty phase voltage. Then in the second step, the extinguishing moment of the secondary arc is detected in the case of transient occurrence, in which the reclosing signal is sent to the side circuit breakers of the PTL after the secondary arc is completely extinguished. The major features of the proposed scheme are: its capability to detect the permanent fault from the transient one, and determine the extinguishing moment of the secondary arc without the need to define a specific threshold level, its independence from the PTL type and its appropriate structure that facilitates its online hardware implementation and makes it more comprehensive. Extensive simulations in the ElectroMagnetic Transient Program‐RV, as well as practical data testing, demonstrate the accuracy and precision of the proposed method. [ABSTRACT FROM AUTHOR]