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In this paper, novel neutral reactor structures are proposed to mitigate the secondary arc current (SAC) in non-conventional Multi-circuit Multi-voltage Transmission lines (MCMVTLs). The parameters of the reactors in the structure are optimized using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimization algorithm, coded in Python, regulates the multiple runs of an Electromagnetic Transients (EMT) simulation program to minimize the secondary arc current. The optimization trials are run in parallel on a 64 core computer to minimize the solution time. A detailed arc model was tested on the EMT program (PSCAD). Using this model and optimized parameters in the proposed neutral reactor schemes, the SAC is indeed extinguished in acceptable times. The SAC and TRV for neutral reactors with optimized parameters are up-to 68 and 77%, respectively, lower than the ones with parameters calculated by the conventional approach which ignores inter-circuit coupling. Meanwhile, the extinction times are up-to 46% faster. As a result, single-phase auto-reclosing in MCMVTLs is viable.

An electric potential appears at floating wires located within a strong electric field. This phenomenon can be used to supply small isolated communities situated close to Extra-High Voltage transmission lines. This non-conventional distributed generation system has been studied for the last years. However, to improve the power generation system the optimal position of the floating wires, number of wires used, bundle radius, and type of wires must be properly identified. This paper presents a mathematical model solved with genetic algorithm to design a collector system with optimized induced voltage and minimized project cost, identifying the optimal reactor used for voltage regulation. The algorithm was applied to design a collector system that can tap-off 100 kW from a 230 kV transmission line. The trade-off between objectives and the Pareto optimal solutions were evidenced via several simulations using the weighting sum approach. These results allowed to identify a final geometry according to a-posteriori designer preferences.

This paper describes a new method to represent single-phase overhead transmission lines (TL) under corona effect in electromagnetic transient simulation program. Based on Bergeron model and the scheme proposed by Dommel to represent transmission lines in Electromagnetic Transients Programs (EMT), a voltage-dependent line model (VDLM) was developed. This model can be represented through of an equivalent impedance network and easily combined with other components of the electric power system. To solve the nodal equations of the network a simple technique is proposed, which is suitable to calculate lightning overvoltages transients and avoids the necessity of iterative methods, increasing the efficiency of the algorithm. The proposed method was implemented in Matlab software, and the simulation's results were compared with field measurements to verify the accuracy of the model. Comparisons were also made with the traditional linear Corona Model. A good agreement could be observed between them.

This paper presents an analysis of resonant faults and their transient responses on half-wavelength lines. This type of transmission line has been studied for many years in countries that need alternatives for bulk power transmission over very long distances. An important issue for this technology is the occurrence of critical faults, which produce peculiar behavior in the main electrical entities and can jeopardize line insulation and compromise system stability. Here, the main factors influencing the severity of faults are analyzed: the type of fault and fault location. This paper shows that faults involving positive and negative sequences are the most critical when applied at specific regions and produce high voltage and power with a high rate of rise. The necessity for a mitigation method that removes this severe resonant fault condition until the operation of a protection system is discussed, and such a method is established. A method using two spark gaps with a new and improved location criterion is proposed, tested and evaluated, providing promising results for controlling voltage and power at terminal substations. Digital simulations are performed with PSCAD/EMTDC.

This study describes the hardware implementation of a fast adaptive single-phase auto reclosing algorithm based on voltage harmonic content measurement. The proposed algorithm classifies the fault type, preventing reclosing onto permanent fault, and identifies the arc extinction instant, adjusting dead-time to implement reclosing with granted success. The hardware was connected to the Real Time Digital Simulator (RTDS) to perform tests in hardware-in-the-loop (HIL) with a protective relay. The studied system is based on a 500 kV transmission line of the Brazilian electrical power system and eventually real case oscillograms were tested. The algorithm performance was validated with previous software development. However, in the present document we highlight the importance to implement hardware test, as operational limits can only be identified in this last testing stage. Robustness of proposed algorithm based on low-order voltage harmonic content was proved with oscillograms’ tests.

This paper analyses low-cost techniques for rural electrification based on the use of insulated shielding wires of extra-high-voltage transmission lines. The main idea is to use the line capacitive coupling as an auxiliary power supply to remote rural systems. The insulated shielding wire (ISW) will behave as a capacitive voltage divider, promoting low voltage on it. We introduce a comparison of different low-cost electrification methods used over the last years and present a careful analysis of different topologies, which have a major impact on rural voltage regulation. A transient study was implemented to observe the behavior of both the transmission system and the rural feeder under typical switchings.

This paper presents a detailed study of half-wavelength (HWL) transmission line system under critical fault conditions. This non-conventional ultra high voltage alternating current (UHVAC) transmission line has excellent properties in steady-state operation condition and economic advantage when compared to conventional UHVAC system and even high voltage direct current (HVDC) transmission systems for similar power capacity. This technology has been studied for many decades and its response under condition fault is an important topic. First, the point of fault and the type of fault conditions are evaluated to confirm that balanced faults in specific regions are critical. Then the main characteristics of voltage response of HWL transmission system under balanced fault are presented and critical regions that produce severe overvoltage are identified and main transient characteristics are described. Finally, a preliminary mitigation procedure is shown and its performance is evaluated.

Single-phase autoreclosing (SPAR) is among the alternatives for mitigating the many harmful effects that a line-to-ground fault in a transmission line (TL) may cause. This procedure basically consists of opening the compromised phase, waiting a preset time span (dead time), and recomposing the previously isolated phase. In the vast majority of SPAR implementations, the open phase switching proceeds with no guarantee of whether the TL is still faulted. Switching the open phase into a fault might represent a more severe threat to the system than simply disconnecting the TL in the first place. Hence, in an effort to ensure higher levels of operational reliability to SPAR, the present paper offers a new methodology to check the soundness of the open phase during the dead time before its reclosing. First, the method's fundamental concepts are exposed. Second, a huge number of steady-state tests are presented, for which both the system topology and its operative condition were varied. To conclude, the SPAR is simulated in the time-domain with the most critical condition found in the steady-state analysis. The proposed strategy was capable of correctly identifying whether the system was faulted in every performed simulation.

A study of the AC link with flexible transmission distance and half wavelength properties as an option for bulk power transmission over very long distances is presented. This alternative has been studied for many years, however, the present document introduces new insight and explanations about how the use of adequate optimisation methods of tower design and tuning procedures permits that AC transmission lines with half-wavelength properties present enhanced performance that could be comparable with high-voltage DC transmission systems. Issues highlighted in this work are: improvement of right of way size, flexible distance, adequate voltage-reactive power regulation and the competitive system efficiency. Competitiveness of this AC link based on half-wavelength properties is proved when old problems are eliminated.

This study presents a new phase selector algorithm and fault type classification for very long transmission lines, known as the half-wavelength lines (HWL). For this work, the Clarke components variation rate method applied to current magnitudes was used. The method was implemented in a real-time digital simulation hardware-in-the-loop (HIL) test environment. We applied different fault types at each 5% line length, obtaining Clarke component current phasors. The proposed algorithm is stable for the native behavior of the half-wavelength line, including the resonance zones and their mitigation procedures. In addition, the algorithm is immune to the fault insertion angle, fault resistance, and line loading level. Finally, the algorithm could be applied in commercial microprocessor-based relays or could be used as a post-fault analysis tool.

In this paper, a careful analysis of directional element behavior applied to a half-wavelength transmission line (HWL) is presented. Single line-to-ground (SLG) faults were applied, varying loading conditions and fault resistance. A commercial relay was used. Two directional elements were considered: 32QG and 32V. With the aim of obtaining directional element setting parameters, a Python program based on two-port network theory was developed. The simulations were also performed in a hardware-in-the-loop (HIL) environment. It was observed that only the element 32V operated properly throughout the system during SLG fault conditions. It can be concluded that the conventional directional element algorithm can be applied to a system with a half-wavelength transmission line under the above-mentioned fault condition.

This paper presents an analysis of fault phase impedance and its dynamic response for half-wavelength (HWL) transmission lines. One important issue of this technology is fault protection as distance protection elements are based on impedance for conventional AC lines. HWL line has very long length, preventing the direct application of classical impedance method because the capacitance effect produces different impedance behavior. This paper analyzes and characterizes the phase impedance response, and proposes alternative distance protection settings focusing on solving the problem of line-to-line fault detection. It is proven that the algorithm covers 84% of the line length. However, faults in the central region have a high resistance characteristic and cannot be detected with the proposed method. The paper takes into account the influence of line transpositions that further affects the protection performance near central region. Transient analysis and software in the loop tests were performed with PSCAD/EMTDC.

This paper presents a method for estimating the black-box arc parameters using genetic algorithm. The proposed method is applied to represent a DC short-circuit in a railway system protected by a High-Speed Circuit Breaker (HSCB). The simulated cases were compared with experimental data, and the results show very good agreement between model predictions and experiments. This method could potentially be used by HSCB’s manufacturers to extract and provide arc model parameters to end users based on their test results.

In this study, the main results of a new mitigation method to single-phase auto-reclosing switching in half-wavelength transmission lines are presented. Initially, the behaviour of single-phase reclosing on conventional lines was evaluated, then, the results obtained for half-wavelength lines are presented. Finally, the proposed solution for the manoeuvre to be successfully executed is described. The study proposes a very advantageous solution for the application of the single-phase switching in half-wavelength lines.

This study presents the results of technical and economic analysis of high-voltage direct current (HVDC) transmission system and high-voltage alternating current transmission system for bulk transmission over very long distances. The last is a point-to-point transmission that does not need reactive compensation and does not have intermediate substations, the half-wavelength transmission (HWL). Special attention is paid to reliability and ways to meet the N - 1 criteria regarding security and adequacy. Single-circuit lines instead of double-circuit ones are considered for economic and environmental reasons ensuring the same reliability when clearing the most frequent line-to-ground (or single-pole) fault. For this, single-circuit line with reserve phase for HWL and quadripolar single-circuit line for HVDC are proposed. The analysed system considered Brazilian electrical system conditions: 6000 MW transmission over 2500 km. This study highlights the advantages of applying a reserve phase for HWLs and a third converter substation increase to cope with system security with minimum cost. It is shown that the single-circuit HWL with reserve phase has an investment 30% lower than that for HVDC, resulting in a total yearly cost 15% lower.

This paper presents an adaptive single-phase auto-reclosing method based on harmonic voltage measurement through a digital harmonic filter. This filter and the transmission system were modelled in a real-time digital simulator (RTDS). A distance relay was used for protection and reclosing, responding as if it was in field operation. The studied system was based on an actual 500 kV Brazilian system. This work highlights the advantage of using the adaptive technique when compared with regular fixed dead-time procedure.

This paper presents a comparison of secondary electric arcs behavior for reclosing applications. The main objective of the paper is to show the differences in secondary arcs during simulations, laboratory tests and real life events. These comparisons can help engineers develop adaptive reclosing algorithms and improve power system stability. A software arc model, a laboratory test result and field events' harmonic contents were analyzed. Although the harmonics may differ in each method, they all provide enough information to be used in the reclosing algorithms.

This study presents the results of single-phase auto reclosing technique tests, comparing the performance of traditional procedure and fast adaptive procedure. The last is based on the measurement of voltage harmonic content on the transmission line faulty phase terminals. The transmission system used was modelled on the real-time digital simulator with a distance relay and a quality meter to more realistically implement the reclosing techniques. The studied system was based on an actual Brazilian 500 kV transmission system. This study highlights the advantages of using the adaptive technique opposite to the use of traditional manoeuvre.

In this paper, novel multi-circuit transmission line (MCTL) designs with low secondary arc current (SAC) values are proposed. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) was used to generate the optimized tower structures. The aim is to select the MCTL configuration that satisfies multiple objectives such as increased capacity, reduced cost, right-of-way (ROW), and tower height, while satisfying several constraints such as SAC limit, ampacity, electric field, etc. The objective function is formulated as a mathematical function of design variables such as sub-conductor position, phase arrangement, etc., and several constraints. Two-port theory is used to calculate the SAC resulting from different faults along the line, which is significantly faster compared with time-domain Electromagnetic Transient (EMT) simulations. Comparisons of MCTLs with and without SAC constraints are presented, clearly showing the importance of taking into account SAC limits during the optimization process. As a result, MCTL structures with SAC reductions of up-to 64% were obtained, indicating that the MCTL are able to successfully handle Single Phase Auto-Reclosing (SPAR).

This work proposes the use of a novel faulted phase-selection phasor-based algorithm to solve the high-resistance and weak-infeed fault condition selection problem in existent long compensated transmission lines. The algorithm was originally developed for future half-wavelength lines (3000 km for 50 Hz system or 2500 km for 60 Hz), and was slightly modified and tested in a real 645 km 1000 kV Ultra High Voltage transmission system. The algorithm was implemented in a programmable protective relay and tested using a real-time simulator. A series of tests under extreme conditions (such as high impedance fault and very week infeed system together) were conducted to evaluate the performance and robustness of the proposed algorithm.

This paper introduces a nonconventional rural generation system that extracts energy from high-voltage transmission line surroundings. The system was designed for a 230-kV transmission line and consists of a special 20-km collector line and an innovative substation. The energy is coupled to the collector line and supplied through a resonant circuit. There is no physical contact with the transmission line. A detailed electromagnetic study is described, assuring there is no disturbance at the transmission line and that the rural system delivers high-quality energy. Spark gaps were used to avoid overvoltage along the rural feeder. Transmission line reliability is not compromised.

This paper presents a hardware implementation of two current transformer (CT) saturation detection methods and one distorted signal reconstruction method. Those methods have been implemented previously only in software. To evaluate the algorithms performance, a real time hardware in the loop system was implemented with several test scenarios forcing CT saturation. The paper highlights the influence of the quantization error generated by the analog-to-digital-converter in the reconstruction of distorted signal process and introduces a method to determine the best parameters to reconstruct the distorted current signal. The methods used have shown precision and high speed in detecting and compensating distorted current signal in real time, even for the worst CT saturation cases.

This paper presents a relay model based on a manufactured differential transformer relay, SEL-787, developed in a real-time digital simulator. The objective of this study was to develop the model and to compare its performance to the actual relay and to a generic built-in model. With the proposed model, it is possible to implement studies in real-time simulators not only with the physical relay under analysis, but also with the surrounding protection system. The use of many relays for a real-time simulation test can be very expensive and complex. This paper presents the possibility of using models, based on actual relays, in the surrounding areas to cover all possible protection problems. The proposed model presents a new modeling technique and the comparisons to the relay itself and to the built-in generic model were made not only in terms of algorithms but also in terms of response time. The model’s performance was studied for different situations that interfere with the relay daily operation and it presented good adherence to the actual relay. This could not be observed in the built-in real-time simulator model.

The purpose of this paper is to supply technical data for the proposed field energization of 500 kV transmission lines present in the Brazilian interconnected system, forming a line, henceforth called AC-Link, slightly over a half-wavelength in 60 Hz. The purpose of the test is to investigate overvoltages and currents that result from the energization of the AC-Link. This paper shows the results of simulations performed in ATP (Alternative Transients Program) when considering the occurrence of three-phase faults along the AC-Link during energization. The results obtained show that, in certain situations, the overvoltages and energies in the arresters may reach very high values and some specific mitigation procedure should be implemented.

This paper proposes an enhancement on the methodology commonly used for overvoltage analysis motivated by the excitation of electric network resonance points due to injection of harmonic currents by equipment with nonlinear characteristics. The improvement proposed comprehends inclusion of effects caused by nonlinear equipment into the frequency scan study, harmonic content survey, transformation of currents and/or voltages from phase to sequence domain, and application of the Windowed Fast Fourier Transform (FFT). This enhanced methodology was applied in the investigation and identification of unexpected resonant behavior causes observed in pre-operational electromagnetic transient studies for an autotransformer energization.

In this work we propose a new mitigation method to minimize secondary arc current and analyze the behavior of electrical quantities related to the single-phase auto reclosing in half-wavelength (HWL) transmission lines. Initially, such quantities are presented for a half-wavelength line without any device that minimizes the secondary arc current. Following, an innovative new secondary arc current mitigation procedure is presented and implemented. The mitigation method proposed in this work is implemented through the insertion of a circuit-breaker in both transformers neutrals at the transmission line terminals, with the intention of isolating the transformers during fault secondary. Our results show that the behavior of electrical quantities related to the single-phase reclosing switching in such very long line is very different when compared with conventional lines. Their values get close to conventional lines when the proposed mitigation technique is implemented. Furthermore, with the proposed solution the secondary arc has a high probability of self-extinguishing during regular dead-time, allowing the application of the single-phase auto-reclosing switching in HWL. The simulations were implemented in a real time digital simulator.

This paper presents a new approach for designing transmission lines to transmit more power in a narrower space. Multi-circuits lines are a good alternative to attain this objective. However, the optimum solution is not obtained by just positioning several regular single-circuit transmission lines in a single tower structure. Although double-circuit and multi-circuit transmission lines have been used over the last years, there are not many studies about non-conventional multi-circuit transmission lines. Thus, in this research a mathematical model to represent the problem related to increasing the surge impedance loading level of each circuit, and reducing the costs, the ROW and the height of the towers by optimizing their bundle geometry and conductor type by applying genetic algorithms is proposed. The overall transmission lines presented as examples have an improvement between 52% and 149% in the objective function.

This work reports the personal computer implementation of a real-time simulator based on the widely used Electromagnetic Transients Program, version Alternative Transients Program (EMTP-ATP) software for testing protection and control devices. The proposed simulator was implemented on a conventional PC with a GNU/Linux operative system including a real-time kernel. Using foreign models programmed in C, ATP was recompiled with the PortAudio (sound card I/O library) with tools for writing and reading the parallel port. In this way, the sound card was used as a digital-to-analog converter to generate voltage waveform outputs at each simulation time step of the ATP, and the parallel port was used for digital inputs and outputs, resulting in a real-time simulator that can interact with protection and control devices by means of hardware-in-the-loop tests. This work uses the minimum possible hardware requirements to try to implement a real-time simulator. Due to the limitation of two channels, this simulator was used mainly to demonstrate the implementation methodology concept at this stage, this concept could potentially be expanded with more powerful hardware to improve its performance. The performance of the implemented simulator was analyzed through interactions with a real intelligent electronic device (IED). Furthermore, a comparison with the results obtained by means of the well-known real-time digital simulator (RTDS) was presented and discussed.

In this paper, a novel faulted phase selection algorithm is proposed to be used for distance protection applied to half-wavelength power transmission lines. These lines represent an alternating current solution for very-long point-to-point interconnections as an alternative to HVDC. However, no such lines are currently in operation, and if this type of line is to be constructed, it will require its own protection philosophy because of its peculiar characteristics. This paper shows that the fault selection algorithms used in conventional relays do not work properly when applied to half-wavelength lines. The algorithm proposed herein is initially studied in the steady state and ultimately implemented in a programmable protective relay that is tested using a real-time simulator.

Since the human density, technologies, industries and services are in continuous grow, the electrical power consumption increments over the time. To satisfy those power levels the transmission lines should increment their power capacity. However, the increment has to be done taking into account that the line projects should use the lowest possible space to decrease their environmental impact. The present paper proposes the use of optimized multi-circuit transmission lines with several circuits and voltage levels on the same tower. A mixed-integer non-linear programming (MINLP) model with variables in a permutation based space for optimizing the surge impedance loading (SIL), right of way (ROW), costs and height of power transmission lines is presented and solved using evolutionary computation with a multi-objective approach based on the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimization is done by choosing the optimal position, type and quantity of conductors as well as the phase sequence in multi-circuit transmission lines. To deal with the different types of decision variables, a custom constraint handling is proposed. As a result of the optimization process, multi-circuit power transmission lines with narrower ROW, lower environmental impact, higher SIL and similar costs to conventional lines are obtained.

This study involves the application of Short Time Discrete Fourier Transform in order to obtain the harmonic content of voltage between the terminals of 647 artificially generated long electrical arcs. Non-confined tests were conducted on three 500 kV towers specially built inside a laboratory facility, in order to represent as close as possible actual transmission line conditions. The 1-s duration arcs were artificially generated along the 4 m insulator string of a 500 kV tower by imposing a sustained 60 Hz current. The arc voltage harmonic content can be used to identify the moment at which the arc is stabilized in the air and only after this instant measured data can be used to derive mathematical arc model. A statistical analysis of the results, considering only the period for which the arc is stabilized, enabled the establishment of the harmonic signature of the electric arcs for a large arc current amplitude range. From the results it can be stated that an accurate arc model should properly reproduce the presented harmonic content for any arc current level.

This article explains the phenomenon of severe temporary overvoltage (TOV) due to critical faults on a very long transmission line with half-wavelength properties. Such non-conventional AC lines are an alternative to bulk power transmission over very long distances and present excellent steady-state properties. However, half-wavelength lines can present fault cases with very different natures of the voltage response due to fault-resonance conditions. The present document introduces a further explanation of these fault-resonance conditions. First, this study analyses the resonance at the fundamental frequency and analytically determines the TOV considering the fault location, the type of fault, and a simple model of system components. Coherence of major phenomena is obtained with time-domain simulation. Then, a more detailed method for analysing overvoltages on half-wavelength lines under fault conditions is presented. Here, a sensitivity analysis is implemented using PSCAD/EMTDC with more accurate models of system components. Factors such as the type of fault, sequence circuit, fault location, short-circuit level, fault resistance, loading level, transformer saturation and ground resistivity are considered. Finally, the paper interprets the impact of those factors on fault-resonance conditions and TOV.

Este trabalho enquadra-se na linha de pesquisa que tem como objetivo a busca de modelos mais precisos para cálculo de parâmetros de linhas aéreas de transmissão na faixa de frequência 0 a 2 MHz. Esta faixa de frequência cobre a maioria das perturbações eletromagnéticas nos sistemas elétricos (manobras, ocorrências de faltas, rejeições de carga, descargas atmosféricas, perturbações harmônicas). Entre 1 Hz e 2 MHz o solo pode ter a condutividade elétrica da mesma ordem de grandeza que o produto entre a constante dielétrica e a frequência angular do sinal incidente no solo, em função da dependência desses parâmetros com a frequência. Consequentemente, as suposições de baixa frequência tradicionalmente adotadas - condutividade do solo constante e permissividade desprezível - podem levar a modelos que não representam de forma adequada a resposta da linha no caso de transitórios rápidos (com espectro de frequência acima de 1 kHz). É apresentado um estudo dos parâmetros de uma linha formada por um único condutor acima de solo condutor imperfeito, - onde a impedância e a admitância de retorno pelo solo são avaliadas através de métodos tradicionais de cálculo e através de integração numérica das formulações de Carson modificadas para inclusão do modelo de solo com parâmetros dependentes da frequência.

This paper proposes a new control method to reduce overvoltages due to three-phase reclosing for shunt compensated transmission lines (TL). The method detects the first minimum voltage region of the beating across the circuit breakers after protection dead time and works independently of voltage zero crossing, reducing significantly the reclosure time. The controller was tested on a Real Time Digital Simulator (RTDS) and its performance was compared to the traditional preinsertion resistor approach and another existing control method.

The secondary arc extinction is the main concern in single-phase auto reclosure (SPAR) switching studies, since it dictates whether the reclosure will be successful or not. In this context, a function that describes the arc length variation over time (l(t)) is an important information not only for dynamic response but also for the analysis of transient arc processes. Given that purely electrotechnical approach only gives a profile of the curve l(t), the application of techniques based on image analysis has been considered for obtaining such function. In this paper, a new approach based on 3D-reconstruction and the tracking of an electrical arc is proposed for performing a computer-based evaluation of variations in its length. It was applied a three-dimensional active contour named 3D-snake that is geometrically represented by a B-spline, which evolves in 3D space. This new model is much less dependent on the determination of homologous points than the ad hoc approaches found in the literature for recovering 3D geometry of electrical discharges based on image analysis. In addition, the proposal presented is capable of tracking the evolution of the electrical discharge taking into account the time dependence between consecutive pairs of frames in two videos providing the required function l(t).

The energization of long transmission lines can cause high overvoltage stresses not only along the transmission line, but also in the rest of the network. The traditional method of limiting switching overvoltages to acceptable levels is the use of circuit breakers equipped with pre-insertion resistors. The present paper describes a study comparing this traditional method with two other alternatives for the limitation of switching overvoltages during line energization in an actual 500 kV transmission system: the use of metal oxide surge arresters at both line closing of circuit breaker poles. Digital simulations were made with PSCAD/EMTDC software and the degree of shunt compensation is considered as an independent parameter.

In this work some procedures to measure and model soil electromagnetic behavior in frequency domain are presented. The soil samples were collected at Cachoeira Paulista, Brazil, southeastern region (22°41.2′S, 44°59.0′W). The proposed model takes into account the earth conductivity and permittivity frequency dependence. Some procedures to reduce noise signals in the field measurement values are presented. The parameters of an actual 440 kV single three-phase transmission line were evaluated in frequency domain (considering the proposed soil model and the common representation with a constant conductivity and no permittivity), such as longitudinal line parameters, attenuation factor, phase velocity and transfer function. It was possible to identify regions where not considering the proposed model could result in severe error.

The objective of this paper is to show an alternative methodology to calculate transmission-line parameters per unit length. With this methodology, the transmission-line parameters can be obtained starting from impedances measured in one terminal of the line. First, the article shows the classical methodology to calculate frequency-dependent transmission-line parameters by using Carson's and Pollaczeck's equations for representing the ground effect and Bessel's functions to represent the skin effect. After that, a new procedure is shown to calculate frequency-dependent transmission-line parameters directly from currents and voltages of an existing line. Then, this procedure is applied in a two-phase and a three-phase transmission line whose parameters have been previously calculated by using the classical methodology. Finally, the results obtained by using the new procedure and by using the classical methodology are compared. The article shows simulations results for a typical frequency spectrum of switching transients (10 Hz to 10 kHz).

Initially this paper shows the ground wire reduction process for generic multiphase transmission lines and after, the ground wire reduction process for a specific 440-kV three-phase overhead transmission line. Following this, the influence of the ground wire reduction process considering two situations is shown: first, considering frequency independence and second, when these parameters are considered as frequency dependent. This paper presents analytical results for generic multiphase transmission lines. For a specific 440-kV three-phase overhead transmission line, analytical and graphic results are shown considering real data for every frequency between 10 Hz and 1 MHz.

In the presented paper, it is shown how the utilization of a systematic three-phase fundamental frequency analysis and three-phase frequency scan can become helpful tools in an electromagnetic transient study. The present methodology was applied to a study of real transmission system expansion, and it allowed for the identification of some rather severe cases which would be very hard to discover through the ordinary transient study procedure.

Este trabalho apresenta uma técnica alternativa para a proteção de transformadores de potência utilizando a lógica diferencial associada ao uso de Redes Neurais Artificiais (RNAs). Este artifício é utilizado na distinção entre faltas internas e correntes de inrush, que surgem durante a energização do transformador. O programa EMTP-ATP (Electromagnetic Transients Program) foi escolhido como ferramenta computacional para a simulação do transformador de potência com o objetivo de gerar dados de treinamento e testes para as RNAs. Um programa em linguagem FORTRAN foi implementado a fim de avaliar o algoritmo completo da proteção diferencial e resultados promissores relativos ao novo método foram obtidos.

The quality of electric power has been a constant topic of study, mainly because inherent problems to it can lead to great economic losses, especially in industrial processes. Among the various factors that affect power quality, those related to transients originating from capacitor bank (CB) switching in the primary distribution systems must be highlighted. In this work, the characteristics of transients resulting from the switching of utility CBs are analyzed, as well as factors that influence their intensities. The conditions under which these effects are mitigated can then be investigated. A circuit that represents a real distribution system, 13.8 kV, from Cia Paulista de Forca e Luz (CPFL—a Brazilian utility) was simulated through the software Alternative Transients Program ( atp ) for purposes of this study. Finally, a comparison with real-life data recorded at the distribution system was performed in order to validate the present simulation.

This paper describes the quasi-modes three-phase transmission line model, a new model to represent three-phase transmission lines in transient studies, with proper representation of the frequency dependence of longitudinal parameters. A unique transformation matrix—the Clarke matrix—is used for the entire frequency range. As this matrix is a real one. it can be modeled through ideal transformers. The circuit equations, which lead to the matrix modeling, are presented. This line model can be implemented in any digital program with R , L , C and transformer components.

This paper presents a new model to represent multiphase transmission lines in transient studies, including the frequency dependence of longitudinal parameters. The frequency dependence is represented with synthetic circuits, with a cascade of π-circuit for each mode. A real transformation matrix is used for the entire frequency range and it is modeled through ideal transformers in a transient program like ATP, as described. An application of the methodology is presented for an actual 440 kV single three-phase transmission line where some transients results simulated in ATP are presented. The model is compared to two ATP line models, JMarti and Semlyen.

This paper presents a new model to represent multiphase transmission lines in transient studies, including the frequency dependence of longitudinal parameters. The model uses the exact modes, for ideally transposed lines, and "quasi-modes" for nontransposed lines. For the latter it is necessary to have a vertical symmetry plane. The frequency dependence is represented with synthetic circuits, with one /spl pi/-circuit for each mode. The transformation matrix used for the entire frequency range is the Clarke's one and as it is a real matrix it is modeled through ideal transformers. The model is described for three-phase lines and double three-phase lines. An application of the methodology is presented for a 440 kV single three-phase transmission line where it is made mode analysis, statistical energization and frequency scan analysis. The simulations are performed in EMTP with the proposed model and with a frequency dependent EMTP line model, the Semlyen one, supposing a transposed and nontransposed line.

A new component transformation is proposed for six-phase systems, applicable for six-phase transmission lines studies, allowing its representation by two uncoupled three-phase lines. Cyclic transposition allows additional properties of the two three-phase groups that are presented. Transposed and nontransposed six-phase lines are analyzed, and the main characteristics of their natural modes are discussed in the frequency domain. An eigenvector normalization method for nontransposed lines that assures null modal conductance and, as a consequence, positive modal resistance, is proposed. Numeric results are presented in relation to an example line of 500 kV/sub rms/, phase to ground, with characteristic power of 5176 MW. >

Neste trabalho foi realizada uma extensa análise de sensibilidade dos parâmetros elétricos longitudinais e transversais de uma linha de transmissão trifásica em função da freqüência. Uma linha real de 440 kV foi utilizada como base para a parametrização. Na análise de sensibilidade variaram-se as seguintes características da linha: diâmetro dos cabos pára-raios, diâmetros dos condutores fase, altura dos condutores, distância horizontal entre as fases e geometria dos feixes das fases. Para cada variação, observou-se o comportamento dos parâmetros em termos das parcelas das matrizes primitivas e em termos de componentes modais. Em relação à modelagem, o trabalho contribuirá para o desenvolvimento de novas metodologias e de fórmulas simplificadas para cálculo de parâmetros aplicado a análise de transitórios de manobra. In this work a large sensitivity analysis of longitudinal and transversal electrical parameters of a three-phase transmission line in frequency domain was performed. An actual 440 kV transmission line was used as reference. In sensitivity analysis, the following line characteristics were varied: ground wires diameter, phase conductors diameter, height of conductors, horizontal distance among phases and vertical spacing within external phase bundle. For each line characteristic, the performance of electrical parameters in frequency domain, in terms of primitive and modal matrices was observed.

Neste trabalho otimizamos o valor de reator de neutro para conseguir minimizar a corrente de arco secundário em sistemas de transmissão com compensação reativa em derivação. Através de uma análise de sensibilidade conseguimos identificar valores de reator de neutro para os quais se consegue uma alta probabilidade de auto-extinção da corrente de arco secundário para diferentes sistemas de transmissão visando assegurar uma manobra abertura/religamento monopolar com sucesso. O método para identificar o reator de neutro ótimo e os valores das correntes de arco secundário para linhas típicas do sistema brasileiro é apresentado. Inthis workwe optimize the neutral reactorvalue in orderto minimize the secondary arc current in transmission systems with shunt reactive compensation. Sensitivity analysis was conducted to identify neutral reactor values that will promote high probability of self-extinction the secondary arc current in different transmission systems to ensure a success single-phase opening/reclosure maneuver. The method is presented to identify the optimum neutral reactor and also values of the secondary arc current for typical lines of Brazilian system.

A paper representation of soil behaviour for transient studies is presented. Such representation is more accurate than the most common procedures of engineering practice and, in several conditions, lead to results with important differences. The proposed model takes into account the earth's conductivity and permittivity frequency dependence, which normally are not considered. One of the aspects covered in the paper is the importance of properly considering the earth's electromagnetic behaviour when calculating transmission line parameters. Some comparisons are presented for an actual 440 kV three-phase transmission line in which the soil behaviour is represented through a unique real value of conductance (the normal approach) and through the proposed model.

This article presents a new model to represent transmission lines including the frequency dependence of longitudinal parameters. The model uses the natural modes, for ideally transposed lines, and ‘quasi-modes’ for non-transposed lines, and is applied to lines that have a vertical symmetry plane. The line is represented through π -circuits, with one π -circuit for each mode. The transformation matrix is modeled using ideal transformers. The model is described for three-phase lines, dc lines, double three-phase lines and six phase lines. A 440 kV three-phase transmission line illustrates it and is compared with a frequency dependent EMTP line model, the Semlyen one.