Alternative Transients Program Research Articles

Methodology to accelerate the statistical assessment process of evaluating the transmission line lightning performance

The lightning performance of transmission lines is a criterion of utmost importance to be evaluated in transmission system reliability. In order to accurately estimate the expected number of shutdowns, it is imperative to account for the stochastic nature of the lightning phenomenon. In this sense, the most widely used technique to estimate these shutdowns is the Monte Carlo method (MCM). Although the MCM is a trustful method, it has a huge drawback in terms of computational burden. Therefore, this paper proposes the use of an alternative statistical technique, the Unscented Transform method (UTM). This method achieves an approximate non-linear mapping by employing a set of points (associated with input statistical data), which are deterministically selected and weighted. The set of these points and weights is then used to estimate the lightning overvoltage across insulator strings, which represents a significant reduction in the number of samples evaluated in the process in relation to the application from MCM. In this paper, the MCM and UTM methods are applied and compared in the lightning overvoltage evaluation, which is carried out with the help of the Alternative Transient Program (ATP). From the studies conducted, it was found that the application of UTM in place of MCM allowed for significant computational gains while maintaining satisfactory levels of accuracy in the estimation of indicators.

Switching Overvoltage Reduction Using Surge Arrester, for 400 KV-line Connecting Khoms and Gmmra Substations

Transient overvoltage in power systems is one of the most important issues to be considered for system stability. Switching surges is an important reasons that cause transient overvoltage. This paper presents a full study of the high-voltage line connecting KHOMS and GMMRA substations. The study utilizes the Alternative Transient Program (ATP) to compute the transient overvoltage due to switching surges (line closing and re-closing); as well as presenting the usage of surge arrester to reduce the upper limit of transient overvoltage. The results present the positive effect of using surge arrester switching element to limit transient overvoltage and keep it at certain level; in addition to damping the isolation in the voltage waveform.

ATP-EMTP simulation of lightning protection system for multi-storey building

Multi-storey buildings with occupied highly technological instruments have more attraction possibilities of a lightning stroke than ordinary residential buildings. A protection system against lightning is necessary for these buildings and the level of the protection system performance is an issue to be examined. In this study, a protection system for a three-storey building is simulated in Alternative Transient Program-Electromagnetic Transients Program (ATP-EMTP). Distributed-parameter line models are used for the conductors of the protective system by modelling vertical conductors as nonuniform lines. The currents flowing in the critical conductors and the voltages at some critical points resulting by a lightning stroke are computed. The conventional lighting parameters required for structural protection such as lightning peak current, current rise time and time interval for the current flowing are determined. The effect of the radius of conductors in the protection system on the surge response is investigated.

Evaluation of Medium Voltage Distribution Network with/without Distributed Generation using ATP Software

This research has as main objective to analyze the contributions of a distributed generation unit when connected to a medium voltage distribution feeder (13.8 kV). The behaviour this electrical system is evaluated following the occurrence of some disturbances. Before this, all the modelling of the electrical system was performed using ATP - Alternative Transients Program. Three types of disturbances were simulated: phase-to ground short-circuit, islanding of part of the electrical system and load increase on the feeder. To easy the comparisons, all studies were carried out with and without the presence of the distributed generator taking into account the following variables: busbar voltage profile, output power provided by the substation and by the distributed generator when present.

A Computational Contribution to Analyse the Connection of an Independent Power Producer to the Grid

The main objective of this paper is to present the modelling and performance of a synchronous generator connected to a distribution system to study the impacts of the expansion of distributed generation. Computer models for synchronous machine and its speed governor and voltage regulator were developed in the Alternative Transients Program (ATP) in its interface called ATPDraw. The implementation of such modelling has been developed in order to meet the requirements of companies in the energy sector, as well as to make a visual interface of easy understanding. To validate these modelling, some performance studies are realized for the synchronous generator of an Independent Power Producer (IPP) connected to the distribution system. The roles played by the speed governor and voltage regulator are highlighted when a severe contingency such as a three phase short-circuit occurs in the system.

Induction Motor Capacitances Calculation Using FEA for Common Mode Current Studies in ATP

The prediction of common-mode currents in inverter-driven induction motors is necessary to propose mitigating solutions in order to prevent failures and ensure the proper operation of the entire electrical system. The motor model for these high-frequency studies is relatively simple; however, to find its parameters accurately is a very complex task. In this context, this paper presents an alternative to estimate leakage capacitances in induction motors, based on the finite element technique, through computational simulation using FEMM (Finite Element Methods Magnetics). Then, an application of the motor capacitances in an appropriate model for common-mode quantities determination is shown as an example, using the ATP (Alternative Transients Program).

Analysis of the Influences of Changes in Gains and Time Constants in a Power Factor Regulator Using ATP-EMTP

The objective of this study is to analyze the influence of the gains and time constants in a control system of a Power Factor Regulator. This regulator was modeled using the “TACS –Transients Analysis Control System” routine "ATP-EMTP - Alternative Transients Program". This regulator is connected to a synchronous machine of an independent producer, and later, is observed the behavior of machine speed in steady state, the rms voltage and power factor is observed in the PCC (Point of Common Coupling) of the system. Finally, appropriate conclusions about the influence of the gains and time constants for the regulator power factor is conducted, seeking a system that behaves as stable as possible, taking into account the rules related to the insertion of distributed generators in the Electric System.

Gangguan Saluran Transmisi di Deteksi Menggunakan Metode Gelombang Berjalan dan Transformasi Wavelet Diskrit

Determination of fault location using impedance-based methods and the traveling wave method. Many previous studies used the impedance method but found deficiencies; if the fault impedance is high, it affects the accuracy of determining the fault location. Another method uses the global positioning system (GPS), which is less economical because it requires a lot of expensive devices. This research focuses on the traveling wave method popularized by Bewley, which uses high-frequency electromagnetic impulses derived from transient voltage and current faults inside and outside the line. This method ignores the fault type, line resistance, and fault start angle. In analyzing the time difference between the incident and reflected waves, a discrete wavelet transform analysis is used to help determine the location of the disturbance. The Maninjau hydroelectric power plant and the Pauh Limo substation are modeled using an alternative transient program (ATP) with several components and parameters. Modeling is given for one-phase ground disturbance, two-phase ground disturbance, two-phase, three-phase, and lightning surge. Determination of fault locations using single-ended and double-ended methods with a sampling rate of 1 Mhz by varying the type of wavelet (Daubechies 4, Coiflets 4, Symlets 4) The results obtained in determining the location of disturbances based on the type of wavelet, Daubechies 4, have a small error, so the accuracy is high, and the method double ends for all types of interference to obtain a smaller error rate.

A novel method of overvoltage suppression due to de-energization of shunt reactor in high voltage system

<span lang="EN-US">Substations usually employ shunt reactors to reduce the reactive power of systems. Due to current chopping when the shunt reactor is shut off, a high frequency and amplitude overvoltage is generated. This study was aimed at eliminating switching-related overvoltages in shunt reactors so as to maintain the equipment, prevent insulation failure, and avoid reignition. Therefore, the circuit was modified according to the suggested mitigation strategy to verify that transient overvoltages are suppressed by the circuit breaker and shunt reactor. With a view to evaluate the existing chopping caused by the switching of reactor bank, the alternative transients program (ATP-Draw) model was used to simulate the transients resulting from switching a shunt reactor. This work has been put into practice for various current chopping values. The collected results of the simulation showed that the proposed model was significantly highlighted for the suppression of overvoltages, with the voltage across the circuit breaker being reduced from 679 KV to 478 KV at a current chopping value of 5 A and from 351 KV to 152 KV across the shunt reactor.</span>

Using the Exact Equivalent π-Circuit Model for Representing Three-Phase Transmission Lines Directly in the Time Domain

This paper presents a novel three-phase transmission line model for electromagnetic transient simulations that are executed directly within the time domain. This model relies on distributed and frequency-dependent parameters, as well as employs modal transformation for its implementation. The single-phase model of the exact equivalent π-circuit is utilized for each propagation mode. This model combines discrete components, such as resistors, inductors, and capacitors, to accurately emulate the transmission line behavior via linear circuit elements. This model can be seamlessly integrated into various electrical circuit simulation software, thus allowing easy utilization and incorporating time-varying elements to analyze transmission lines. The JMarti model, which comes by default in the Alternative Transient Program, and the numerical Laplace transform method implemented in MATLAB were utilized to validate the proposed solution across various scenarios. An advantage of this model is its independence from the prior calculation of travel time and its exemption from convolutions, inverse Laplace transforms, and Fourier transforms, thus streamlining the simulation process.

Simultaneous series and shunt earth fault detection and classification using the Clarke transform for power transmission systems under different fault scenarios

For high-voltage (symmetric and non-symmetric) transmission networks, detecting simultaneous faults utilizing a single-end-based scheme is complex. In this regard, this paper suggests novel schemes for detecting simultaneous faults. The proposed schemes comprise two different stages: fault detection and identification and fault classification. The first proposed scheme needs communication links among both ends (sending and receiving) to detect and identify the fault. This communication link between both ends is used to send and receive three-phase current magnitudes for sending and receiving ends in the proposed fault detection (PFD) unit at both ends. The second proposed scheme starts with proposed fault classification (PFC) units at both ends. The proposed classification technique applies the Clarke transform on local current signals to classify the open conductor and simultaneous faults. The sign of all current Clarke components is the primary key for distinguishing between all types of simultaneous low-impedance and high-impedance faults. The fault detection time of the proposed schemes reaches 20 ms. The alternative transient program (ATP) package simulates a 500 kV–150-mile transmission line. The simulation studies are carried out to assess the suggested fault detection and identification and fault classification scheme performance under various OCFs and simultaneous earth faults in un-transposed and transposed TLs. The behavior of the proposed schemes is tested and validated by considering different fault scenarios with varying locations of fault, inception angles, fault resistance, and noise. A comparative study of the proposed schemes and other techniques is presented. Furthermore, the proposed schemes are extended to another transmission line, such as the 400 kV–144 km line. The obtained results demonstrated the effectiveness and reliability of the proposed scheme in correctly detecting simultaneous faults, low-impedance faults, and high-impedance faults.

Evaluation of the transmission tower and frequency-dependent soil parameters influence on the grounding potential rise waveforms

In this paper, the influence of the transmission tower and the frequency-dependent soil parameters on the grounding potential rise (GPR) waveform is evaluated. This evaluation is performed using a physically consistent electromagnetic model that determines the transient behavior of the grounding system submitted by lightning, together with the Alternative Transients Program for the representation of aerial elements (tower, phase cables and shield wires). This model was developed in the frequency domain and, in this way, allows the inclusion of frequency-dependence of soil electrical parameters. In this sense, three formulations of the dependence in question are considered, widely disseminated in the literature, and determined through systematic measurement processes. The results illustrate that the concomitant inclusion of the tower and the frequency-dependence substantially modifies the GPR waveforms, when compared with those in which isolated grounding is considered, especially for soils with high resistivity values and for first return strokes. This is of most importance when evaluating personal safety criteria in the transmission tower vicinity. In these situations, the GPR waveforms should be determined by considering the presence of the tower and not only with the isolated grounding, since the transient step and touch voltages are directly associated with GPR.

An interpolation-based solution to use low sampling rate records in traveling wave-based fault location methods

This paper presents an interpolation-based solution that allows the application of traveling wave (TW)-based algorithms even using sampling rates lower than those typically considered as a requirement for classical approaches. Two phasor (PH)-based and one TW-based fault location methods are compared with the proposed technique and applied through Alternative Transients Program (ATP) fault simulations in a 500 kV/60 Hz Brazilian double circuit series-compensated transmission lines with high-voltage direct current lines (HVDCs) and static var compensators (SVCs) in the vicinity. The results show that the proposed interpolation-based technique is reliable and suitable for TW-based fault location using data records with sampling rates lower than those used in commercially available equipment. Moreover, its accuracy is comparable to classical TW-based fault location solutions, revealing its usefulness for practical application when only traditional digital fault recorders (DFRs) are available.

Analysis of overvoltages across line insulator strings considering the ground-wire and phase conductors corona

This paper assesses the influence of corona effect on the overvoltages developed across the insulator strings of overhead transmission lines due to lightning. The influence of corona is investigated considering lightning strikes to the tower top and shielding wires at midspan. A large range of soil resistivity and lightning currents peaks are evaluated in the analysis, and the stress across the insulator strings is evaluated applying the integration method. Simulations are carried out in the Alternative Transient Program (ATP/EMTP), wherein the corona effect is represented through the accurate Suliciu corona model, which was implemented using the MODELS interface and combined with J. Marti line model. Furthermore, it was also represented the wideband behavior of tower grounding system. Results showed that corona effect has a minor influence in the overvoltages across the insulator string for strikes to the tower top. However, it strongly influences the overvoltages across line insulators ensuing from a lightning strike to the shielding wire at the midspan, leading to a decrease in the peak value of the lightning current that causes line flashover.

Evaluation of single-ended impedance-based transmission fault location using fixed and variable window phasor estimation approaches

In this paper, the performances of fixed and variable window size phasor-based techniques reported in the literature are evaluated on a classical one-terminal impedance-based fault locator, pointing out the challenges and alternatives for applications in transmission systems equipped with high-speed protection functions. To do so, several Alternative Transients Program (ATP) fault simulations were carried out in a 230 kV/60 Hz power network, varying their parameters such as type, location, inception angle and resistance. The obtained results attest that phasors estimated from variable window size strategies may improve the fault locator performance, even in the first cycles after the disturbance occurrence, appearing themselves as potential alternatives to be applied in combination with high-speed phasor-based protection routines.

Traveling wave-based fault locators: Performance analysis in series-compensated transmission lines

In this paper, the performances of one-ended and two-ended traveling wave (TW)-based fault location techniques in series compensated transmission lines (SCTLs) are thoroughly investigated, highlighting the impact of the series capacitors (SCs) and their associated overvoltage protection on such routines. To do so, a diversity of fault simulations were carried out on a realistic Alternative Transients Program (ATP) power system model of a 500 kV/60 Hz double-circuit SCTL located in the north region of Brazil. From the carried out studies, it is demonstrated that the two-ended algorithm is not impacted when the SCs are installed at the line ends, but the single-ended routines based on correlation functions are more affected by the SCs banks, even though some promising results may be obtained depending on their adjustments.

Three-parameter ATP/ATPDraw transmission line high impedance fault model

This paper presents a three-parameter transmission line high impedance fault (HIF) model for the Alternative Transients Program (ATP)/ATPDraw. Real-world HIFs caused by vegetation contact on lines belonging to a Brazilian utility are firstly investigated to identify representative features of the fault resistance behavior during the disturbance period. Then, a data regression method is applied to obtain a time-domain function which emulates the fault resistance. Finally, an ATP/ATPDraw transmission line HIF model is developed and described in detail. For the sake of simplicity, only three parameters are proposed to be used in the model, namely: Initial resistance, final resistance and resistance decaying time constant. To prove the proposed model is representative, real HIF records are compared against ATP/ATPDraw simulated ones. The obtained results show the proposed model satisfactorily emulates the effects of real HIFs.

Tower-foot grounding model for EMT programs based on transmission line theory and Marti's model

This paper proposes a tower-foot grounding system model compatible with EMT programs which might be useful for the simulation of lightning transients in overhead lines. The proposed model is based on the solution of the telegrapher's equations and the application of the classical Marti's transmission line model. The model is implemented in the Alternative Transients Program (ATP) and validated considering a benchmark electromagnetic model. Its accuracy is evaluated and shown both in terms of the simulated ground potential rise (GPR) and line overvoltages developed through the insulator strings due to lightning currents. Finally, the model accuracy is also demonstrated in terms of the line backflashover outage rate.

Fault diagnosis in bipolar HVDC systems based on traveling wave theory by monitoring data from one terminal

This paper proposes a method for detecting, classifying and locating incident faults on transmission line (TL) of a bipolar HVDC system. This method is based on the traveling waves theory and uses the redundant discrete wavelet transform to filter voltage signals monitored at only one system terminal. The model represents the Brazilian HVDC system of the Madeira River, which is simulated in the Alternative Transient Program (ATP). Different fault scenarios are analyzed, being generated by varying type, resistance and fault location. Moreover, in order to make the simulation more realistic, the TL is modeled based on frequency dependent parameters. Thereby, the impacts of line parameter uncertainties and transient attenuation on the proposed method are analyzed. From the obtained results, it is concluded that the method correctly detects all fault types through the use of a self-adaptive detection threshold. Furthermore, it is verified that the self-adaptive threshold detects the fault times instants with an efficiency superior to the fixed threshold. In the classification step, all faults were correctly classified through rules elaborated based on the voltage variation level. Finally, the total average errors of fault location represents only 0.047% of the TL extension. Moreover, it is verified that fault location errors for pole:pole faults were inferior to those obtained for pole:ground faults, being the efficiency of the method inversely proportional to the fault resistance.

Equivalent grid-following inverter-based generator model for ATP/ATPDraw simulations

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.