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This article presents a methodology to calculate grounding potentials in adjacent electrodes present in high-voltage substations subjected to a short-circuit current dissipated in the main grid. The contribution of the technique is the consideration of the coupling by the soil among electrodes taking into account a two-layer soil and irregular geometry of the conductors. This problem is of special concern due to the presence of passers-by near metallic fences, not directly connected to the grounding grid, whose potentials usually have not been evaluated. In this context, the article presents a general analytical formulation aiming to estimate the potential in multiple electrodes, leading to a possible risk to human beings close to the substation. Sensitivity studies are performed in order to evaluate the effect of the soil resistivity and the distance from the faulted grid and the coupled electrode. A practical application in a substation grounding system is discussed. Finally, a huge grounding system is evaluated in order to verify the robustness of the proposed formulation.

This paper deals with the effects of soil inhomogeneity in the equation that describes the grounding resistance. This issue is relevant in order to circumvent the classical assumption that the soil is homogeneous and that the equivalent geometry of the grid is hemisphere. As the medium homogeneity is a rare condition in real soils, supported by the Average Potential Method and by the Images Theory, a derivation in the existing analytical formulation to calculate the grounding resistance in non-homogeneous soils is proposed for different equivalent grounding systems. The study is validated and supported by simulations performed in the software Ansys Maxwell 3D.

The fault location technique based on the electromagnetic time reversal (EMTR) theory has demonstrated great success on different kinds of power networks. Previous work has presented good results from its application on multiterminal HVDC systems, although the modelling considered in this work was not as realistic as possible. Since the method uses fault-induced electromagnetic transients, the modelling of the converter stations and the HVDC links can impact the results of the technique. This work thus brings a further evaluation of the EMTR-based fault-location method on a point-to-point HVDC transmission link upon simulation data, as the previous work, but using sophisticated modelling. The converter stations and the cable link are modelled with the most complete models available in EMTP-RV, to resemble the real condition of fault in the simulations. Pole-to-ground and pole-to-pole faults are simulated with different values of resistance at two different locations along with the cable link. The observed results show a great influence of the fault resistance, being the accuracy of the fault location estimation low only in some situations.

This paper deals with improvements related to the application of the Fall-of-Potential Method to measure the substation grounding grid parameters considering short distances between the grounding system under test and the auxiliary current electrode. The improvements are related to: (a) use of material with low resistivity value around the auxiliary current electrode to increase the current between this electrode and the earth electrode system under test; (b) proof that the measured potentials (touch and step) is conservative (in favor of safety) due to the coupling effect between electrodes and (c) obtain a curve and an expression that allows to determine the position in which the potential electrode should be placed to estimate the grounding grid resistance of the substation under test.

Electric arcs caused by damages in wiring and electrical connections of an installation may result in fire. Conventional protection devices, such as circuit breakers, fuses and residual-current circuit breakers (RCCBs) are not capable of detecting this disturbance. New equipment, such as the Arc Fault Devices Interrupter (AFDI) have appeared in the last two decades with the purpose of meeting such demand. However, their application and efficiency are still restricted due, mainly, to the masking deriving from disturbances generated by some types of charges present in the power grid. Making such detection more robust and accurate is not a trivial task and, therefore, new methodologies have been developed in recent years. Considering such context, the purpose of this work is to assess the disturbances caused by serial arc faults through experimental tests and use of Wavelet Transform (WT) on the detection of the phenomenon. Based on the results, it was possible to develop a sorting model that produced very satisfactory outcomes. The model was developed through concepts of the support vector machine (SVM) and presented average accuracy around 90% even in critical detection situations.

The surge impedance of a grounding grid is a mandatory parameter to be considered in the project of a Lightning Protection Systems (LPS). As these parameter determinates de proper design and ensure the reliable operation of the associated grounding structure, its practical understanding is required. In this context, based on in situ measurements, the present work investigates if the surge impedance of a wind turbine (WT) grounding system presents significant values differences in two distinct situations: (i) when only the grounding grid and WT foundation were built and (ii) after the complete construction of the WT including the tower, nacelle and blades. The investigation is based on a statistical study supported by Analysis of Variance (ANOVA). Considerations about the measurement procedures are presented and experimental data are discussed. Preliminary results indicate that there is no significative difference between values from both scenarios. Moreover, recommendations are proposed in order to improve the data reliability to further investigations.

The insertion of renewable and distributed energy resources and the use reduction of fossil-fuel-based ones have been in the spotlight of studies of the scientific community in general. Aiming at an efficient connection interface for these resources and at the reduction of distribution losses, the employment of a Low Voltage Direct Current distribution system (LVDC) is considered in this study. For this purpose, the modification of a pristine Low Voltage Alternate Current distribution system (LVAC) to a DC one is proposed without network’s rerouting and with minimal adaptations. Both systems were implemented in the electric power distribution system simulator, OpenDSS (open-source code), and compared to their losses, energy transferred to the loads, voltage drops along the line, as well as number of conductors required for their operation.

This work presents a two-dimensional Transmission Line Modeling (TLM-2D) method for modeling non-homogeneous media and non-linearities. The presented method is derived on top of the classical TLM-2D method with reactive and conductive stubs to modify the properties of the medium. Taking advantage of the analogy between electromagnetic and circuits theories, nonlinearities such as soil ionization, can be solved numerically through models formulated to represent electrical conductors, such as grounding systems. Using this analogy, the analysis can be extended more generically to non-homogenous and lossy media. Then, nonlinearity phenomena is included in the classical TLM-2D model through the dynamic variation of circuit parameters. This variation is obtained through the developed analytical based tests. Computational implementation details are also reported. A case study is presented considering a grounding grid mesh in non-homogeneous media submitted to lightning surges. Comparative test results with the state of the art highlight the improved precision of the presented solution.

Arcos eletricos causados por danos na fiacao e em conexoes eletricas de uma instalacao podem resultar em incendio. Os dispositivos de protecao convencionais, como disjuntores, fusiveis e disjuntores diferenciais residuais (DDRs) nao sao capazes de detectar esta perturbacao. Novos equipamentos, como o Arc Fault Devices Interrupter (AFDI) surgiram nas ultimas duas decadas com o intuito de suprir tal demanda. Contudo, a sua aplicacao e eficiencia ainda sao restritas devido, sobretudo, ao mascaramento proveniente de disturbios gerados por alguns tipos de carga presentes na rede eletrica. Tornar esta deteccao mais confiavel nao e uma tarefa trivial e por esse motivo, nos ultimos anos, novas metodologias vem sendo desenvolvidas. Neste contexto, o objetivo deste trabalho e avaliar as perturbacoes causadas pelas faltas arco serie atraves do uso de um prototipo de gerador de arco artificial, cujo respectivo transitorio e processado sob o enfoque da analise em Multiplas Resolucoes (MRA) provida pela Transformada Wavelet Discreta (DWT). Os resultados experimentais demonstraram que a energia relativa dos sinais decompostos, associada ao seu correto condicionamento e capaz de detectar faltas arco tipo serie para cargas resistivas com bom grau de precisao.

A penetracao de veiculos eletricos (VEs) nos Sistemas de Distribuicao de Energia Eletrica (SDEE) ja e uma realidade mundial, sendo que nos proximos anos tal insercao tende a ser massiva. Neste contexto, o trabalho propoe a analise dos impactos tecnicos (desequilibrio e violacao de tensao) em uma rede de media tensao de um SDEE devido ao carregamento em massa de VEs. Para a analise, sao utilizados os programas computacionais Open Distribution System Simulator (OpenDSS), para a realizacao dos calculos de fluxo de potencia e Load Profile Generator (LPG), para gerar perfis de cargas residenciais considerando a insercao desta tecnologia. A fim de avaliar a aleatoriedade das variaveis que afetam diretamente o carregamento de VEs, assim como a localizacao dos carregadores no SDEE, o metodo de Monte Carlo e utilizado. Este estudo e realizado em uma rede base de 23 nos. Como contribuicao sao analisados e quantificados os impactos causados por uma conexao de VEs na rede, nao coordenada e em grande escala, bem como a influencia nos indicadores estabelecidos pelas regulamentacoes vigentes.

The electromagnetic time reversal (EMTR) theory has been used as a base for the development of a new method for fault location, whose application has been demonstrated in many previous works. Seeking a contribution to the current studies, the present work aims to evaluate its performance against incipient faults in underground distribution systems. The incipient fault simulation is performed on an actual underground distribution network in the direct-time phase using a static model for the arc voltage in ATP-EMTP. A constant fault resistance is used in the reversed-time phase for the range of guessed fault locations. The influence of the fault resistance value in the reversed-time phase is analysed and the results show that the EMTR can be applied for the accurate location of incipient faults on the main feeder of the system for some values of the constant fault resistance. However, some weakness is observed for incipient faults on a branch, which may be related to the modelling followed. These results might be interpreted as preliminary ones to future works with better approaches.

The paper proposes an innovative numerical model-based on Transmission Line Modeling method (TLM) for the representation of ground meshes including the nonlinear soil disruption phenomenon. In the presented model, the soil ionization is represented by the temporal change of conductive components taking into account the residual resistivity retained in the ionized region. Simulations are performed for a ground mat submitted to an impulsive surge. Comparisons with the state-of-the-art solutions are presented and demonstrate that the proposed technique is appropriate for representation of elaborated grounding grids, resulting in a faithfully and more accurate numerical model. Ease of implementation without hard-to-design parameters, highlight the model attributes for practical purpose.

The soil forms the basis of grounding studies and the main steps to obtain its model are: the acquisition, processing and interpretation of soil resistivity data. This paper refers to the processing stage, which were obtained through field measurements. In this context, the aim of this work is to present a methodology for the treatment of measured apparent soil resistivity data using the Wenner 4-Electrode Method in the area where a substation grounding grid will be installed. The methodology is characterized by the minimization of an objective function, which is applied to a set of measured apparent soil resistivity values in the various directions where the measurements were carried out. The comparison of the methodology that minimizes an objective function with the procedure that is usually applied on the ground grid design (arithmetic average of the measured resistivity data) indicated that both methodologies provide different models for the soil structure. However, the method usually adopted by designers should be used with caution, especially when there are significant variations in the apparent soil resistivity values. The optimization method aims to find the equivalent resistivity value of the soil which presents the smallest deviation between measured and calculated apparent soil resistivity values.

Since voltage interruptions, sags and swells are Power Quality (PQ) disturbances with great economic impact, studies that seek alternatives to mitigate its effects have been conducted extensively. The PQ Brazilian standard names these disturbances as Short-Duration Voltage Variations (SDVVs), classified them in terms of magnitude, duration, and frequency of occurrence. These parameters are used to calculate the Impact Factor (IF) of SDVVs, a severity-characterization index of their incidence. In this context, this work assesses the influence of three-phase transformer winding connection and neutral grounding on the quantities of SDVVs and the IF observed by an industrial consumer in a distribution system. Fault simulations at ATPEMTP perform the study, considering two different winding connections for the secondary transformer and applying a grounding resistance to the neutral of the main transformer of the distribution system. The SDVVs are verified in two different ways: phase-to-ground and phase-to-phase voltages. It is observed that there are differences in these quantities and for the value of the IF due to the winding connection of the secondary transformer, the value of the neutral grounding resistance of the main transformer and the ways of voltage verification.

The effectiveness of overcurrent protection on power systems concerning single-line-to-earth (SLE) faults is strongly related to the adopted neutral-earthing philosophy. Different arrangements of neutral earthing are employed for electric distribution systems (EDSs), being the unearthed, resistance-earthed, inductance-earthed and resonant-earthed designs commonly so-called noneffectively-earthed methods. SLE-fault currents can be very low in these cases, not sensitizing overcurrent-based devices. However, the voltage on the faulted phase decreases, while the voltages on non-faulted phases increase, giving rise to undervoltage and overvoltage conditions. Hence, it is possible not to be restricted to overcurrent-based philosophies but additionally uses overvoltageand undervoltage-based ones. In this sense, this work presents a study of both overvoltage and undervoltage protections combined as a new method for SLEfault protection, aiming the application on noneffectively-earthed EDSs. A relay in ATPDraw is modelled to trip when an undervoltage occurs at one phase and overvoltages occur at the others. ATP-EMTP simulations are performed on a representative EDS, noneffectively-earthed through a neutral earthing resistor (NER), considering different values for the fault resistance and the NER. The results show that the new method is more effective than the overcurrent protection for SLE faults on noneffectively-earthed systems, tripping even when that is not able to do.

In many cases, simulations of electrical power systems (EPS) require more realistic representations of their components. As the behavior of the protection system plays an important role in several types of EPS studies, it is relevant for the improvement of the protection devices’ models. Thus, in this work, an expulsion fuse model to be used in ATP-EMTP simulations is proposed. The model considers the melting and arcing periods with mathematical approximations and yields well-estimated results for the fuse opening times in fault simulations performed in a study-case system. It is observed, that the proposed model describes the expulsion fuse characteristics in a satisfactory way.

This paper presents a proposal of impact assessment of short-duration rms voltage variations using fuzzy logic. The index IF (Impact Factor) of the Brazilian power quality regulation standard is the evaluation parameter. The fuzzy logic is used to represent the vagueness in the disturbance magnitude and duration measures. The method is used with computationally generated power quality signals. According to the results, the fuzzy assessment seems to be a good method to represent the impact of the disturbances at a consumer taking into account the uncertainties in the measures of voltage magnitude and duration.

Considering urban substations ground grid diagnosis, some real-physical constraints result in measurement process challenges: 1) limited length between electrodes used to measure the equivalent impedance of the grounding system; 2) to determine the current that flows from ground grid conductors to the earth; and 3) to determine the grid resistance. In this scenario, an adequate diagnosis of the safety offered by the ground grid under test when a ground fault occurs is not a trivial task. This article describes a methodology that allows a reliable diagnosis regarding the safety provided by a substation ground grid. The methodology is applied to the parameters obtained in performed field tests. The method has two steps. First, the fall-of-potential method with reduced distances between electrodes is used to determine the equivalent impedance of the grounding system. Then, the ground current is obtained. In both stages, optimization techniques are applied to the specific equations that govern the phenomenon under investigation. Comparative case studies considering real-life data illustrate the effectiveness of the method.

This paper shows one way to calculate grounding potentials in adjacent electrodes presented in high voltage substation coupled by soil to the main grounding grid in a two- layer soil. This problem is of special concern due to the presence of passers-by near metallic fences, whose potentials usually have not been evaluated, not directly connected to the grounding grid. In this context, the paper presents a general analytical formulation aiming to estimate the possible risk to human beings close to the substation. In order to do that, the generated potentials originating from a short-circuit in the electric power system are calculated considering the coupling by soil between the main grounding system and the adjacent electrode (the metallic fence).

In this paper a frequency domain formulation for nonlinear arcing fault location is presented. The proposed fault location formulation uses as input data first cycles after the fault inception voltages and currents. The formulation is based on circuit analysis and a parameter estimation method. To consider the main characteristics of nonlinear arcing faults, a time varying resistance embedded in a nonlinear model is proposed and used. The formulation is developed for the case of the most frequent single line-to-ground faults using phase components. The effects of fault inception angle, time-varying series resistance, source impedance, load flow, sampling frequency and others factors are investigated and analyzed. This new approach was successfully tested through computer simulation and real data obtained from a Southern Brazilian Energy Utility. The proposed method was developed as dedicated software and is currently used by CEEE-GT.

This paper presents the development of an analytical formulation for estimating the potential on the soil surface, caused by electric current calculated on a grounding conductor. The formulation has a great significance in its use in conjunction with 1-D numerical methods, which are not able to determine such potentials directly. The proposed study focuses on lightning surges considering the frequency dependence of the soil properties. First, the subject is introduced emphasizing important aspects related to the analysis and representation of grounding systems against lightning. Afterward, the proposed analytical formulation is introduced with a focus on the computational implementation of the transmission line modeling method in 1-D. Simulations were carried out considering a typical horizontal electrode used as grounding in the power electric system. The formulation was validated by comparing the results with the solution based on the electromagnetic model (CDEGS Software), which is considered the most stringent for the solution of full Maxwell equations due to their minimum approaches. The results demonstrate that the generalized formulation presents good accuracy, contributing to an improved representation of grounding systems based on numerical techniques in 1-D.

We present an analysis aimed at evaluating the effect of the presence of the tower on the measurement of the grounding impedance. The Numerical Electromagnetics Code NEC-4 is used for the full-wave modeling of the structure including the tower and its footing grounding system, as well as the experimental setup used for the measurement of the grounding impedance. First, the effect of possible path-dependence in the evaluation of the integral of the electric field is investigated. It is shown that, up to a frequency of about 100 kHz or so, the voltage, and consequently the evaluated impedance are independent of the path of integration. At higher frequencies, differences appear, which might be significant especially for poor conducting ground. The effect of the distance to the reference remote earth on the evaluated voltage is also analyzed and it is shown that a distance of 100 m to the remote earth is appropriate to evaluate the grounding impedance potential rise. The simulation results show that at low frequencies (up to about 200 kHz or so for the considered 140-m tall tower), the effect of the presence of the tower can be disregarded. At higher frequencies, the evaluated impedance is affected by the presence of the tower. The poorer the ground conductivity, the more significant the effect of the presence of the tower on the evaluated impedance. Two injected current waveforms, representative of typical first and subsequent return strokes, are considered for the time-domain analysis. The effect of the presence of the tower can be significant for subsequent return stroke excitation, which has a wider frequency spectrum compared to first return strokes. It is shown that in the early-time region, part of the injected current flows into the tower. For a ground conductivity of 0.001 S/m, the tower peak current increases to about 10% of the exciting current, for the case of a subsequent strokes. It is also shown that the presence of the tower would cause a decrease in the peak potential rise leading therefore to an underestimation of the so-called impulsive grounding impedance.

This paper analyzes the influence of transformers winding connection and transformers neutral grounding mean on the prediction of voltage sags indices according to Brazilian standard Prodist. The case study was performed on the IEEE 13 Node Test Feeder. Voltage sags were obtained by symmetrical and asymmetrical faults simulations in all systems nodes. One node with a MV/LV transformer was chosen to be a sensitive customer connection node. Several simulations changing the transformer connection and transformer neutral grounding were performed. It was found that both features have strong influence on the voltage sags indices at the sensitive customer node.

In this work, an experimental investigation of the grounding system behavior of tall wind turbines in both time and frequency domains is presented. Two scenarios were considered: in the first one, measurements were carried out on the grounding system embedded in the wind turbine foundation, before assembly of the wind turbine itself; in the second one, the complete wind turbine (tower, nacelle and blades) was included. The study also presents an enhanced signal processing technique for noise cancelation in a harsh electromagnetic environment. In the analysis, the frequency dependence of the grounding impedance was evaluated and a numerical simulation in steady state was performed. The simulation model leads to a satisfactory representation of the studied system. Preliminary results show that the evaluated grounding impedance is not significantly affected by the presence of the complete wind turbine at the evaluated frequencies.

This paper proposes an integrated impedance and transient-based formulation for fault location in distribution systems. The technique uses an extended apparent impedance analysis in order to estimate the fault distance, taking into account the unbalanced operation, intermediate loads, laterals, and time-varying load profile of distribution systems. The fault distance information is used in calculating characteristic frequencies associated to each possible fault location. A transient analysis is proposed to evaluate the spectral content of the fault-generated traveling wave, thus identifying its most significant frequency components. Based on the time–frequency correlation it is possible to eliminate the multiple estimates obtained from the impedance-based method, thus resulting in a single fault location. Aiming to verify the application of the proposed methodology, simulations were carried out in the ATP/EMTP Software considering a real distribution feeder with 3472 buses.

This paper presents a study about the influence of different types of soils and surge wave characteristics in terms of human safety. The study is focused on the step, contact and transferred potentials generated by a lightning striking a grounding system and the produced potential gradients that a person could be exposed to. Initially, an introduction about the subject is made. After that, some important aspects about the grounding systems and human body representation are presented followed by a discussion regarding to the survivability threshold and the model parameterization. A Transmission Line Modeling Method and a circuit based model are used to represent the grounding system and the human body. Several simulations were performed in order to analyze the behavior of the current passing through the heart. It was found that soils with different properties do not affect the possible harmful currents considering the step potential mechanism. On the other hand, in the case of contact and transferred potentials, the soil characteristics have significant influence in the survivability threshold.

This paper presents an extended methodology based on the transmission line modeling method (TLM) aiming at a soil ionization representation for the simulation of grounding systems. This natural phenomenon can be represented by considering the variation of the conductive components present in the TLM circuit. The proposed analytical formulation is introduced with a focus on the computational implementation of the TLM method in one dimension. The method is not subject to divergent solutions, being numerically stable and the methodology can be incorporated into a general algorithm irrespective of the soil properties or characteristics of the grounding electrode and lightning surge.

This paper presents an extended TLM-2D numerical technique. Extensions include simultaneous consideration of non-homogenous media and ionization phenomena representation. Performance evaluation and representation of impulsive grounding systems embedded in concrete are considered as a study case. Analysis based on the Alternative Transients Program (ATP) and field measurements with different grounding systems configurations are presented and discussed.

This paper presents a comparative study of impulsive grounding systems encased in concrete (namely UFER grounding). Several topologies used in transmission and distribution networks as well as in industrial plants were evaluated considering soils with different properties. Scale measurements (in an electrolytic tank with soil) were carried out in order to quantify the performance of this grounding system. The study discusses the performance of different grounding configurations: 1 rod; 2 rods; counterweight; cross and grid embedded in concrete. The results show that the use of UFER grounding can reduce significantly the value of the grounding impulsive impedance both in soils with low and high resistivity for the different evaluated configurations.

This paper presents a systematic study of impulsive grounding systems embedded in concrete. Several topologies used in transmission and distribution networks as well as in industrial plants were evaluated considering soils with different properties. Case study analysis using the Alternative Transients Program (ATP) and real life measurements in scaled configurations were carried out. The aim of this work is to present a contribution with respect to performance assessment of most used grounding system types embedded in concrete.

This paper shows one way to calculate grounding potentials in high voltage substation fences coupled by soil to a grounding grid in a two-layer soil. This problem is of special concern due to the presence of passers-by near metallic fences, whose potentials usually have not been evaluated, not directly connected to the grounding grid. In this context, the paper presents a general analytical formulation aiming to estimate the possible risk to human beings close to the substation. In order to do that the generated potentials originating from a short-circuit in the electric power system are calculated considering the coupling by soil between the main grounding system and the adjacent electrode (the metallic fence). Finally, the proposed methodology is tested and validated using different grounding topologies.

This paper presents the development of a multi-objective optimization explicit model for distribution systems restoration. The main goal of the methodology is to determine the combination of maneuvers devices to be operated in order to maximize the number of customers with restored supply in the post-fault period and to minimize the time required by the process. The proposed formulation considers devices with arbitrary operation times, allowing the representation of automatic and manual maneuvers switches as well as, their effects on the duration of outages. In the proposed methodology, the supply restoration of distribution systems is formulated as a Mixed-Integer Linear Programming model. The proposed methodology was validated using a real distribution system. It is being implemented in one of the computational modules of the “SIRIs Platform” (Smart Grid Simulator), currently under development by NEO DOMINO and UFRGS in a research project supported by CELESC Distribuicao S.A., Brazil.

This article presents a methodology for optimal distributed generation (DG) allocation and sizing in distribution systems, in order to minimize the electrical network losses and keep acceptable voltage profiles. The optimization problem considered equality and inequality constrains, 24 hours power load levels, operational voltage limits, conventional power flow, DG placement with binary variables and sizing of active and reactive power. The optimization problem is solved by mixed integer nonlinear programming (MINPL) using KNITRO solver.

This paper presents a optimization approach for solving the distribution systems' restoration problem. The problem is formulated as a goal programming model aiming to establish the combination of devices to be operated in order to maximize the number of customers restored in the post-fault period as well as to minimize the time required by the network reconfiguration process. This approach considers devices with arbitrary switching times, allowing the modeling of operation of automatic and manual switches. The viability of restoration is ensured through operational and topological constraints, including the system's voltage profile, spare capacity and the radial post-reconfiguration topology. A linear version of the power flow in terms of nodal injection of current is proposed in order to take into account such constraints. The equations are formulated as functions of the state of available sectionalizing switches in the feeder. A case study using a real distribution feeder is used to demonstrate the technique and the optimal solutions of the model obtained in reduced processing times.

This paper presents the EMC (Electromagnetic Compatibility) philosophy applied to design the grounding systems of GIS Insulated Substation - GIS indoor substation. The grounding systems are characterized by the following subsystems: Main Grounding grid (60 Hz Grounding System), Equipotential Grounding grid (HF Grounding system) and Lightning Grounding system. The real case measurements for 100 MVA, 69/13.8 kV GIS indoor distribution substation indicated that adopted EMC philosophy is appropriate because the maximum measured potential difference among the various grounding systems of GIS indoor substation was approximately zero volts and the maximum measured touch voltage was less than 1.4 volts.

This paper presents an analytical mixed-integer linear programming model to improve reliability of distribution networks through the optimal allocation of automated switching devices. Optimal reliability is formulated as a multi-objective problem of minimizing customers' interruptions and the investment costs related to devices' acquisition, relocation and operation. In order to establish the optimal trade-off between these conflicting objectives the Goal Programming approach is proposed. The presented model considers post-fault restoration constraints which limit load transfers and thereby the system reconfiguration capability. Restoration feasibility is ensured by a linear formulation of power flow equations as functions of geographical locations of automated switching devices in the feeder. Therefore, the model's solutions provide a more effective and economic application of automated switching devices, so that voltage and system capacity constraints are taken into account in selecting optimal locations of devices. The proposed methodology was validated using the IEEE 123-bus test feeder.

This work proposes a new method to identify non-technical losses in typical Electrical Power Distribution Systems (EPDS). Aiming to improve the efficiency of on-site inspection for fraudulent clients, the consumers are classified in suspects and non-suspects using the Optimum-Path Forest (OPF) classifier. The authors propose an improvement to this method using results of a Distribution State Estimator (DSE) and geographic information. The method is tested in the IEEE 123 Bus Test Feeder considering a group of consumers for each load. The consumers are based on typical Brazilian residential consumers. The results indicate that the proposed method improves the performance of previously developed techniques and is suitable for both typical and smart EPDS. The best results are obtained when the DSE and OPF are associated using normalized data as the input for this hybrid approach, with expected success rate of up to 72.43% for on-site inspections in the EPDS test system.

This paper presents a study which analyzes the performance of rural distribution lines against the occurrence of lightning. The ATP-Draw program was used to simulate the electromagnetic phenomena and to evaluate the transients caused by lightning discharges. The model of the distribution system is based on the representation of its elements (poles, insulators, equivalent circuit, cross-arm and grounding system). The elements are modeled by its electrical parameters. In the proposed study the rural feeder was represented taken into account the frequency dependence of its parameters. Three topologies of distribution lines are analyzed. A comparative analysis of their performance is discussed.

Energy supply is a significant resource for economic and social development. Power systems statistics shows that the lightning phenomenon is one of the most important causes of power systems outage. In this context, the paper present a study of the performance of a 23kV distribution line related to the occurrence of direct lightning in a particular point of the system, with focus in a comparative analysis of different feeders and poles configurations. The analysis is based on the calculation of flashover and backflashover using ATP-Draw version of the EMTP. The differences of the performance between the horizontal and the vertical feeder configurations with grounding system are demonstrated through the comparison of the maximum lightning current withstand by the feeder. Non-linear grounding resistance and variability of the resistivity of the soil were considered. Simulation results show that the configuration with guard-wire can improve the immunity up to 100% related to the maximum lightning current that the feeder withstand.

This paper presents a study of the behavior of distribution feeders against lightning, where the magnitude of the surge caused by this phenomenon is calculated. The feeder model and the lightning phenomena have been implemented in the electromagnetic transients program ATP-Draw. The magnitudes of the surges are obtained by numerical simulations in this program. Simulations were performed for cases where the lightning impacts the wire-guard or the phase conductor. A sensitivity study to establish the parameters that influence the maximum values of the surge is also performed. The model is applied to a rural distribution line in southern Brazil, where very often lightning causes insulation failure and power cuts. The results show how to improve the feeder protection in order to enhance the level of system reliability.

This paper presents a hybrid method for fault location in distribution networks. An impedance-based fault location formulation, taking into account unbalanced operation, presence of intermediate loads, laterals, and time-varying load profile was developed in order to estimate the fault distance. The faulty section is then identified through the transient evaluation with focus on high frequency analysis using different signal processing techniques. The proposed method was evaluated using a real distribution feeder with 241 buses, simulated through the ATP/EMTP software considering different fault types, resistances and locations.

This paper presents a study about the influence of the different types of soils and surge wave characteristics in terms of human safety. The study is focused on the step, contact and transferred potentials generated by a lightning reaching a grounding system and the produced potential gradients that a person could be exposed to. A Transmission Line Modeling Method and a circuit based model are used to represent the grounding system and the human body. Several simulations were preformed in order to evaluate the behavior of the current passing through the heart.

This paper presents an extended formulation for fault location on electric distribution systems based on one-terminal measurement of apparent impedance. The method is developed using phase-components analysis to account for the inherent unbalanced operation of distribution feeders. Since distribution loads present a stochastic variation through time, a technique for compensation of load variation in both magnitude and angle is also presented. The proposed developments include two general fault location equations that account for any fault type. An iterative algorithm to compensate the line capacitive current component is also provided, thus enabling the application of the technique to long rural and underground systems, in addition to overhead distribution systems. Test results show the accuracy and robustness of the fault location algorithm to different fault types, distances and resistances, considering system's load profile variations up to ± 50%.

This paper presents a study about the influence of the wire-guard as a protection system in overhead distribution line in comparison with unprotected topology against lightning. A real feeder was considered as a case study using ATP-EMTP software. Practical aspects related to the modeling of a distribution line are presented. Simulation results show that the shielding configuration ensures a protection significantly better than the actual topology, around 10 times in terms of lightning peak current. Thus, the wire-guard can improve the immunity of distribution system against atmospheric discharges.