Alternative Transient Program-Electromagnetic Transient Program Research Articles

Support Vector Machine Parameters Optimization for 500 kV Long OHTL Fault Diagnosis

Faults can seriously damage high-voltage (HV) power systems, particularly if they occur on the long overhead transmission line (OHTL) that connects the nuclear power plant (NPP) to the electrical grid. Finding OHTL problems quickly and accurately is essential for the economy, safety, and dependability of the HV power systems. It is essential to pinpoint the problematic phase to avoid unneeded power outages. Thus, one of the most crucial research challenges is now how to identify, classify, and locate OHTL faults. In this study, transient current with high frequency oscillations that arise immediately after a defect at the sending end is investigated in a single-circuit, single-side fed Egyptian 500-kV HV long OHTL. Asymmetric and symmetric faults and locations are also represented in the Alternative Transients Program-Electro Magnetic Transients Program (ATP/EMTP) simulation model under varying fault resistance and inception angles. The proposed solution in this paper is an Optimized Support Vector Machine (OSVM), whose characteristics are optimized via a mutant particle swarm optimization (MPSO) method to detect 500 kV long OHTL faults. The localizer model is also built for practical applications, including power system noise contaminating fault signals. The findings prove that the suggested approach locates the fault in 0.012 seconds from the start of the event, with a 0.0098 percent average percentage error, and without being impacted by differences in fault distance, fault resistance, noise, or fault inception angle. Additionally, the optimised classifier reaches a 99.85% accuracy rate, enhancing line system dependability and advancing nuclear system development.

Electromagnetic Transients in Multi-Voltage Transmission Lines during Non-Simultaneous Faults

It is vitally important that a transmission network provides a continuity of electricity to end users and that the transmission system operator prioritizes its safety and reliability. This article presents the possibilities of using multi-track overhead lines with varying levels of rated voltage, run on a common support structure. This solution would ensure safe operation of the system, reduce the area used for the construction of new overhead lines, and, at the same time increase the transmission network capacity. This article focuses on the method of modeling overhead lines for the analysis of electromagnetic transient states that occur during non-simultaneous disturbance phenomena. This article presents the idea of multi-circuit, multi-voltage lines and their validity of use in power systems. An analysis of electromagnetic transient states for non-simultaneous disturbances in multi-path, multi-voltage lines is presented. This analysis has been made on the basis of a network model, using ATP-EMTP (Alternative Transients Program-Electromagnetic Transients Program) software for solutions, for a Polish power system. Particular attention was paid to the most unfavorable phenomena appearing in the modeled system. The impact of the emerging electromagetic transients in multi-path, multi-voltage lines was evaluated. It was shown that the specificity and rapid changeability of the emerging electromagnetic transients and lack of a universal model of the overhead power line make the analyses of electromagnetic transients highly labor-intensive and time-consuming. Each change is connected with the necessity to create new line models for the study of electromagnetic transient states dependent on many factors.

Ferroresonance Overvoltage Mitigation Using Surge Arrester for Grid-Connected Wind Farm

Ferroresonance occurrence represents a very dangerous phenomenon to electric power systems. Concerning the recent trend of the applications of grid-connected wind farms, this phenomenon can lead to undesired overvoltages stressing the wind farm components. In this paper, the ferroresonance overvoltages are studied and mitigated for the grid-connected wind farm. Single-pole switching of the breaker is considered, where it is the most famous reason behind the ferroresonance transient events in the electric power systems. During the ferroresonance period, the transient voltage of the network is increased to more than three times the voltage level and associated with harmonics. Surge arrester is suggested to mitigate the ferroresonance transient overvoltages, in which the arrester coordination setting of its residual voltage is selected to be 1.2 of the nominal voltage value. Evaluation of the dynamic interaction of the installed surge arrester with the ferroresonance overvoltages is investigated, and the mitigation is attained, successfully. Furthermore, the magnitudes of the harmonics created due to ferroresonance are reduced by installing the surge arresters, but they are not diminished completely. However, the arresters are found under stress if their dissipating energies exceed the withstand capability. The simulations are carried out using the alternative transient program/electromagnetic transient program (ATP/EMTP), and the waveforms are digitally processed using MATLAB software.

Investigation and Improvement of Standard External Lightning Protection System: Industrial Case Study

In this study, the lightning protection system and grounding system of one plant of the petrochemical industry were investigated, evaluated, and improved. The methods used in this study were rolling sphere and angle protection methods. The grounding system of the building under study was modeled and simulated using ATP/EMTP (Alternative Transient Program/Electromagnetic Transient Program) software. The results show that the external lightning protection system of the prilling tower studied does not adhere to IEC 62305 and IEC 1024-1-1 standards. Moreover, the grounding configuration of the DCS building was not appropriate for protecting sensitive equipment inside. Lightning causes an enormous potential difference between lightning ground rods in the grounding system. Additionally, disabling the existing surge protective device (SPD) causes an increase in the magnitude of Ground Potential Rise at the DCS building. Improvement of the lightning protection system of the prilling tower and DCS building on Plant 1 of this petrochemical company as well as some other recommendations for improvements are proposed. This paper also shows evidence that external lightning protection, internal lightning protection, and the grounding system need to be connected to make an exemplary lightning protection system.

A Study on the Out-of-Step Detection Algorithm Using Time Variation of Complex Power-Part II: Out-of-Step Detection Algorithm and Simulation Results

One of the established unstable power swing (out-of-step) detection algorithms in micro grid/smart grid power systems uses a trajectory of apparent impedance in the R-X plane. However, this algorithm is not suitable for fast out-of-step conditions and it is hard to detect out-of-step conditions exactly. Another algorithm for out-of-step detection is using phasor measurement units (PMUs). However, PMUs need extra equipment. This paper presents the out-of-step detection algorithm using the trajectory of complex power. The trajectory of complex power and generator mechanical power is used to identify out-of-step conditions. A second order low pass digital filter is used to extract the generator mechanical power from the complex power. Variations of complex power are used to identify equilibrium points between stable and unstable conditions. The proposed out-of-step algorithm is based on the modification of assessment of a transient stability using equal area criterion (EAC). The proposed out-of-step algorithm is verified and tested by using alternative transient program/electromagnetic transient program (ATP/EMTP) MODELS.

Analysis of Very Fast Transients Using Black Box Macromodels in ATP-EMTP

Modelling for very fast transients (VFTs) requires good knowledge of the behaviour of gas insulated substation (GIS) components when subjected to high frequencies. Modelling usually takes the form of circuit-based insulation coordination type studies, in an effort to determine the maximum overvoltages and waveshapes present around the system. At very high frequencies, standard transmission line modelling assumptions may not be valid. Therefore, the approach to modelling of these transients must be re-evaluated. In this work, the high frequency finite element analysis (FEA) was used to enhance circuit-based models, allowing direct computation of parameters from geometric and material characteristics. Equivalent models that replicate a finite element model’s frequency response for bus-spacer and 90° elbow components were incorporated in alternative transients program-electromagnetic transients program (ATP-EMTP) using a pole-residue equivalent circuit derived following rational fitting using the well-established and robust method of vector fitting (VF). A large model order is often required to represent this frequency dependent behaviour through admittance matrices, leading to increased computational burden. Moreover, while highly accurate models can be derived, the data extracted from finite element solutions can be non-passive, leading to instability when included in time domain simulations. A simple method of improved stability for FEA derived responses along with a method for identification of a minimum required model order for stability of transient simulations is proposed.

Modulation Strategy for Multi-Phase Matrix Converter with Common Mode Voltage Elimination and Adjustment of the Input Displacement Angle

In the last several years, thanks to the development and continuous improvement of semiconductor switching elements, and the simultaneous increase in interest in multi-phase drives, the investigation into constructing multi-phase converters has been growing. The matrix converter (MC) is considered to be one of the contenders for use in the multi-phase drive. In the context of using MC in the drive, it is expected to eliminate the common mode voltage (CMV). Another important problem is the ability to correct the input displacement angle to ensure the operation of the MC with unity input power factor. The purpose of the article is to present an MC modulation strategy that implements both CMV elimination and input displacement angle adjustment. Analytical and simulation analyses of the strategy, in application to three-to-multi-phase MC is presented. The suggested modulation strategy in applying to three-to-multi-phase MC is implemented in ATP-EMTP (Alternative Transients Program-ElectroMagnetic Transients Program) software. Simulation results are provided for a three-to-three-phase three-to-six-phase and three-to-nine-phase MC. The proposed modulation strategy is validated using an experimental approach.

Dominant frequency characteristics analysis of reclosing transient overvoltage in 10 kV cable-overhead hybrid line

Studying the characteristics of reclosing overvoltage is of great importance for risk assessment of reclosing in the cable-overhead hybrid networks because transient overvoltage (TOV) at different dominant frequency can have quite different negative effect to cable insulation. In a hybrid line, when a cable connects with an overhead line (OHL), the surge propagation can become very complex. To clarify the frequency characteristics of the reclosing transient overvoltage in a 10kV hybrid line, in this paper, the simulations are carried out using ATP-EMTP (Alternative Transients Program, Electro-Magnetic Transients Program). The traditional approach to estimate the dominant frequency is suitable for pure cable-based or overhead line-based networks. However, for a hybrid line, due to the difference in line parameters between the cable and OHL, the characteristics of dominant frequency is investigated based on the distributed-parameter theory with new boundary conditions at the junction. According to the variation of dominant frequency considering the source impedance and the wave propagation in the modal domain, the non-monotonous variation of TOV with cable proportion is analyzed. The frequency calculation and the TOV analysis are verified by ATP-EMTP simulation.

Evaluation of a Direct Lightning Strike to the 24 kV Distribution Lines in Thailand

This paper evaluates the effect of a lightning strike directly on the 24 kV distribution lines in Thailand, where such strikes are one of the main causes of power outages. The voltage across the insulator, and the arrester energy absorbed due to the lightning, need to be analyzed for different grounding distances of the overhead ground wire, ground resistance, lightning impact positions, and lightning current waveforms. Analysis and simulations are conducted using the Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to find the energy absorbed by the arrester and the voltages across the insulator. The results indicate that when surge arresters are not installed, the voltage across the insulator at the end of the line is approximately 1.4 times that in the middle of the line. In addition, the ground resistance and grounding distance of the overhead ground wire affect the voltage across the insulator if the overhead ground wire is struck. When surge arresters are installed, a shorter grounding distance of the overhead ground wire and a lower ground resistance are not always desirable; this is because they reduce the back-flashover rate and the voltage across the insulator if lightning strikes the overhead ground wire. However, lightning strikes to the phase conductor result in high arrester energy and the possibility that the arrester will fail. Furthermore, the tail time of the lightning waveform is a significant variable when considering the energy absorbed by the arrester, whereas the front time is important for the voltage across the insulator. In case lightning strikes directly on the connected point between the overhead lines and the underground cables, the distribution line system is protected only by the lightning arrester at the connection point. The overvoltage at the connection point is lower than the basic impulse level at 24 kV of 125 kV, but the overvoltage at the end of the cable is still more than 125 kV in case the cable is longer than 400 m. When the distribution line system is protected by the lightning arrester at both the connection point and the end of the cable, it results in overvoltage throughout the cable is lower than the critical flashover of insulation. This method is the best way to reduce the failure rate of underground cables and equipment that are connected to the distribution line system.

Transient-Based Fault Location on Three-Terminal and Tapped Transmission Lines Not Requiring Line Parameters

In this paper, fault location on three-terminal and tapped transmission lines without requiring line parameters is presented, which mitigates the effect of line parameter variations due to weather and loading conditions on fault-location accuracy. For three-terminal lines, a fault-location method is presented, which utilizes postfault measurements of all three terminals. For tapped lines, two methods are presented. The first one uses postfault measurements of the main two terminals. The second one needs one cycle of prefault measurements at the main terminals as well. Synchronized transient-based measurements are used in methods proposed in this paper. In all of the presented methods, the fault-location problem is converted to an optimization problem and then solved to find the line parameters and the accurate location of the fault. The simulations are carried out by alternative transients program/electromagnetic transients program (ATP/EMTP) software, and the presented algorithms are executed by MATLAB. Simulation results assess the effects of fault resistance, type, and inception angle on the accuracy of the presented methods. Further discussion is also provided on the impacts of synchronization errors, noisy measurements, and nonresistive faults.

The Analysis of Lightning Strikes to MEA’s Distribution Lines on Different Impact Positions

This paper focuses on behaviour of voltage across insulator when the lightning strikes on different impact positions of Metropolitan Electricity Authority (MEA) 24 kV distribution lines in Thailand. The simulations and analysis are performed using Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to investigate the voltage across insulator. The results indicate that when the lightning strikes to phase conductor or shielding failure occurs, the voltage across insulator where the terminal point is more than the middle point is about 1.5 times. This case, the ground resistance and grounding distance of overhead ground wire (OHGW) is not influential on the voltage across insulator. However, in case the lightning strikes to OHGW, the voltage across insulator where the terminal point is more than the middle point is about 1.2 times and the ground resistance as well as grounding distance of OHGW plays an important role for the voltage across insulator. The analysis shows that when the lightning strikes to the terminal line are considerably more severe than the middle line. Therefore, the lightning protection should be specially considered at the terminal point. The peak current magnitude and the front time lightning current waveform are essential parameters when observing the voltage across insulator. However, the tail time is not an important parameter with regard to the voltage across insulator.

Mitigation of Lightning Flashover from Tree to Medium Voltage Aerial Cable Using Shield Wire

This paper presents the performance and protection of medium-voltage (MV) aerial cables against lightning faults by means of laboratory experiment and digital modeling. With the series of laboratory tests, practical examination of lightning hazard to shielded and unshielded aerial cables is conducted, and the need for shield wire protection is established. For the purpose of simulation studies, digital models are developed by using Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP) and its transient analysis of control system features. The performance of lightning flashover overvoltage on shielded and unshielded aerial cable is evaluated with the developed digital models. The evaluation is made by considering a direct lightning strike on wooden poles, messenger wires, and nearby trees. Based on the experimental and simulation results, practical recommendations are proposed for improvement in lightning performance of aerial cables. This study offers possible solutions for the protection of aerial cables against lightning flashover, induced overvoltage, and direct lightning strike, which may improve electricity reliability and availability to customers.

Evaluation of Lightning Overvoltage Protection Schemes for Pole-Mounted Distribution Transformers

Direct lightning strikes to medium voltage (MV) overhead lines cause insulation flashovers in great majority. Generally, the pole-mounted distribution transformers are protected by spark gaps and surge arresters at the MV terminals. In this paper, Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP) simulations have been performed to evaluate the performance of different lightning protection schemes for the pole-mounted distribution transformers. Both first and subsequent stroke currents were considered to estimate the lightning performance of a typical MV unearthed network. The results indicate that the effect of subsequent stroke current is more severe at the low voltage (LV) terminals of the transformer. In case of spark gap protected transformers, the operation of spark gaps produce steep-front overvoltages. As a result, high frequency overvoltages transfer from MV to LV terminals of the distribution transformer that are directly connected to the consumer premises. The steepness of the overvoltages can be mitigated by installing a series filtering element at the MV side of the distribution transformer. Furthermore, surge arrester can be employed to smoothly limit the transient overvoltage at the MV terminals of the transformer in spite of the higher protection cost. Thus, low rating surge arresters in conjunction with spark gaps can be also used to mitigate the lightning overvoltages. Finally, it is recommended that higher energy class surge arrester should be employed for this combined spark gap and surge arrester protection scheme.

Comparison between Parameter of Single Core Unarmoured Aluminium Conductor 6.35/11 kV Underground Cable for Partial Discharge Measurement Using EMTP-ATP Software

Partial Discharge (PD) is one of a symptom in the underground cable before the fault happens.This paper concerned with estimation and detection problems related to PD phenomena in buried underground cables. The Rogowski coil has been implemented to analyze this symptom. The various sizes of nominal cross-sectional area cross-linked polyethylene (XLPE) cable with 6.35/11 KV single core unarmored aluminum conductors that follows Nexans manufacturer datasheet based on design standard IEC 60502 has been used in the simulation using Electromagnetic Transient Program-Alternative Transient Program (EMTP-ATP) software. The Lumped parameter is used for the Rogowski coil sensor model. Meanwhile, for Double-end measurement using J-Marti model is designed to evaluate the parameter changing in the measurement.Based on the measurement, the value of amplitude voltage and current is proportional increase depends on the size of cross-sectional area of conductor XLPE cable.

Grounding Design Improvement to Reduce Back Flashover Rate of 69 kV Subtransmission Line in Power’s Distribution System

This paper presents the grounding design improvement to reduce back flashover rate from the lightning of distribution system. The Purpose to reduce effects of lightning overvoltage from back flashover. And study analysis of the condition effects of lightning performance of 69 kV on Metropolitan Electricity Authority (MEA)’s distribution system of Thailand. The technique objective function is an attachment the external ground wire connected between the overhead ground wires and a ground rod for reduce back flashover. Back flashover is one of the major causes of sustained interruption data. Occurs when the amplitude of lightning overvoltage is more than the limit of insulator strings specification. Then generated flashover on insulator skin and induces the voltage line. This paper simulation with Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP) and analysis of lightning performance in terms evaluated pole top voltage and back flashover rate (BFOR). Result after installing the external grounding design system can reduce the effects of lightning and can improve the reliability in distribution system. And the grounding systems designed is can use for guide line to the features typically at locations subject to lightning damage.

The significance of median natural lightning current strokes on the energy handling capabilities of surge arresters employed in wind farms

The significance of the median natural lightning currents on the energy handling capabilities of surge arresters employed in wind farms is investigated. The Electromagnetic Transient Program Alternative Transient Program (EMTP-ATP) was used to simulate direct lightning strikes to the blade of an existing wind turbine in order to determine the current discharged through the surge arresters and hence the energy absorbed by the surge arresters located at different wind turbines. The values of the energy handling capabilities of surge arresters are generally published in manufacturers' datasheets. Yet, the impact of the subsequent lightning strokes is usually ignored. Also, the published energy handling capabilities are based solely on standard waveforms. This contribution uses two sets of natural lightning current parameters measured on instrumented towers at Mount San Salvatore and Morro do Cachimbo, to simulate lightning strikes to the wind turbine blade. The results show that the influence of the subsequent strokes can be significant for the current discharged through the surge arresters and the subsequent energy absorbed, especially at the stricken turbine.

Relation of Influential Parameters to Back-Flashover on the Insulators in Transmission Tower

This paper focuses on behavior of over-voltage across the cross arm and back-flashover on the insulators with different front times of lightning waveshape. The simulations and analysis are performed using Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to investigate both over-voltage across the cross arm and insulators. The scheme under investigations is a part of Thailand electricity transmission and distribution system. The standard of lightning voltage waveshape (1.2/50 μs) will be compared with the other lightning voltage waveshape front time (4/50 μs) in this paper. The results indicate that the front time of lightning waveshape plays an important role for the back-flashover voltage across insulator as well as the tower footing resistance and the lightning current.

Flexible Synchronized Measurement Technology-Based Fault Locator

This paper presents a flexible and robust numerical algorithm for fault location on transmission lines. The algorithm does not require line parameters to locate the fault, which is an advance over fault locators that do require such information. Line parameters are only approximately constant; they vary with different loading and weather conditions, which affects the accuracy of existing fault location algorithms. Thus, an approach which does not require line parameters would be more robust, accurate, and flexible. Accurately, locating faults on transmission lines is vital for expediting their repair, so the proposed solution could lead to an improvement in the security and quality of the energy supply. Development of the proposed algorithm was facilitated by new smart grid technologies in the field of wide-area monitoring, protection, and control. The proposed algorithm is based on emerging synchronized measurement technology, using synchronized data sampling at both line terminals; however, the “SynchroCheck” procedure is also proposed as a means of accurately locating faults when data sampling synchronization has been lost. This paper presents the algorithm derivation and the results of thorough testing using alternative transients program-electromagnetic transients program (ATP-EMTP) fault simulations.

Research of Off-Grid Household Photovoltaic Power System

The electricity shortage can be effectively alleviated by developing household photovoltaic power system in vast rural areas, it is necessary to establish simulation models. In this paper, the dynamic modeling of household photovoltaic power system including photovoltaic,Cuk-chopper circuit,battery and a single phase PWM inverter have been made in the ElectroMagnetic Transient Program /Alternative Transient Program(EMTP/ATP) software package.Control strategy based on MPPT for the power control of the inverter have been also developed. Operation characteristic of household photovoltaic power system was developed. Simulation results proved the validity of the model.

A discrete wavelet transform approach to discriminating among inrush current, external fault, and internal fault in power transformer using low-frequency components differential current only

This paper proposes an algorithm based on discrete wavelet transform (DWT) for discriminating among inrush current, internal fault, and external fault in power transformers. Fault conditions are simulated using the Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP). Daubechies4 (db4) is employed as the mother wavelet to decompose low-frequency components from fault signals. The ratio between per unit (p.u.) differential current and p.u. time is suggested as an index. The numerator of the ratio is the difference between the maximum differential current and the minimum differential current in terms of p.u. with a base value selected at the transformer-rated current. The ratio is calculated for all three phases, and from a trial and error process the indices for the separation among the internal fault condition, the external fault condition, and inrush condition are defined. The results obtained from the proposed technique show good accuracy for discriminating faults in the considered system. In addition, the proposed algorithm uses data of the differential current with a time of quarter cycle under the analysis. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.