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Electric Power Distribution Systems (EPDS) are steadily growing in both size and complexity, and thereby faults on distribution feeders tend to affect more customers and take more time to be located and fixed. Hence, fast and accurate fault location is of primordial importance in minimizing the economic loses for both customers and utilities. Some methods such as those based on the apparent impedance analysis are able to accurately identify the fault distance from the local terminal. However, as the distribution systems have multiple branches and monitoring infrastructure is usually limited to the substation, the location of the faulted branch is a problem not solved yet. This paper proposes the transient analysis of the fault-generated traveling wave in order to identify the faulted branch of radial distribution feeders. The method is based on the correlation of theoretical frequencies calculated for each wave propagation path and characteristic frequencies inferred from the transient spectrum. A frequency-dependent modal transformation matrix is formulated by modifying the Carson's equations thus allowing to accurately model the propagation of high-frequency transients in unbalanced distribution networks. Aiming to verify the performance of the proposed methodology, simulations were carried out considering several fault scenarios in the IEEE 13 nodes distribution system.

The effects of lightning are the main cause of interruptions in electrical networks (distribution feeders), imposing a crucial impact on power quality and reliability. An exhaustive review of the state of the art shows that avant-garde solutions have not yet presented explicit mathematical models that relate the interdependence of these two phenomena. This paper presents a novel mixed integer linear programming (MILP) model to be utilized in the design of lightning protection systems (LPS) and which aims at minimizing sustained and momentary interruptions in distribution networks while leveraging investment costs. The proposed model considers a selection of different shielding structures and grounding systems. The constraints of the optimization model include technical and economic aspects of LPS implementation. A case study considering a real distribution feeder with 81 buses is presented. Test results highlight the generality of the proposed model and illustrate the potential for real-life application. It is worth pointing out that the proposed optimization model is currently used by a distribution utility as a reliability-oriented tool for LPS design.

Lightning phenomenon is the main cause of power systems faults. These faults may cause momentary or permanent service interruptions, thus system reliability is inherently interdependent with lightning phenomenon. A literature review will show that state-of-the-art solutions have yet to present mathematical explicit models for the interdependency of such two phenomena. In this context, this paper presents a multi-objective mixed integer linear programing (MILP) model for distribution systems reliability optimization while considering lightning phenomenon interdependency. The presented multi-objective MILP model aims the simultaneous minimization of SAIFI and MAIFIE reliability indices and associated costs. These goals are achieved by optimizing the lightning protection system design, which includes selection and allocation of different types of grounding systems along distribution feeders, while considering simultaneously network characteristics. Validation is done using real-life 81 bus 23 kV distribution network data. Test results highlight the efficiency of the presented model in improving system reliability while reducing associated costs. The ease of implementation of design, formulation of parameters and encouraging test results indicate potential for real-life application. The multi-objective MILP model is currently used by a distribution utility as a reliability-oriented tool.

Os sistemas de distribuicao de energia estao constantemente expostos a ocorrencia de faltas, o que torna de primordial importância para as concessionarias que estas sejam localizadas com rapidez e precisao. Embora as tecnicas disponiveis atualmente sejam capazes de estimar a distância das faltas com relativa exatidao, algumas caracteristicas intrinsecas aos sistemas de distribuicao ainda impoem limitacoes a localizacao de faltas em alimentadores radiais. Neste contexto, este trabalho apresenta uma metodologia baseada na analise dos transitorios de alta frequencia gerados pelas faltas utilizando medicoes somente no terminal local. A distância da falta em relacao ao terminal de medicao e determinada atraves da comparacao entre as frequencias caracteristicas identificadas no espectro do transitorio, e as frequencias teoricas calculadas para os possiveis caminhos de propagacao. A formulacao e baseada em um modelo detalhado das linhas de distribuicao, considerando a modificacao nas equacoes de Carson, a dependencia da frequencia e a inclusao dos efeitos pelicular e da corrente de retorno pela terra para altas frequencias. A tecnica proposta foi avaliada considerando simulacoes de faltas no alimentador IEEE 34 barras. Os resultados apresentados incluem a comparacao com um metodo de localizacao de faltas considerado estado da arte atualmente.

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.

A new numerical distance relaying algorithm based on Mathematical Morphology and a Least-Square Curve Fitting has been proposed. It makes use of morphological operators to detect and classify the faults and a Curve Fitting method to estimate the fault distance. To show the effectiveness of the proposed technique, computer simulations have been carried out on a test system, considering several fault types in different locations, loading angle and fault incidence angle. Due to simple mathematics operations used, the protection scheme proposed displays secure and effective high speed fault detection and tripping.

OBJETIVOS: Determinar a prevalencia de dor nas costas e fatores associados em uma amostra representativa da cidade de Pelotas, RS, Brasil. METODOS: Estudo transversal que avaliou 972 adultos com idade entre 20 e 69 anos, de ambos os sexos, moradores da zona urbana do municipio. O questionario aplicado incluiu questoes socioeconomicas, demograficas, comportamentais e de saude. Dor nas costas foi definida como qualquer dor ou desconforto em algum local das costas nos ultimos 12 meses, seja na regiao cervical, toracica ou lombar. RESULTADOS: A prevalencia de dor nas costas foi de 63,1% (IC95% 60,0 a 66,1), sendo a regiao lombar a mais referenciada (40%). Sexo feminino 1,24 (1,12 a 1,37) e percepcao ruim de saude (p

OBJETIVOS: Determinar a prevalência de dor nas costas e fatores associados em uma amostra representativa da cidade de Pelotas, RS, Brasil. MÉTODOS: Estudo transversal que avaliou 972 adultos com idade entre 20 e 69 anos, de ambos os sexos, moradores da zona urbana do município. O questionário aplicado incluiu questões socioeconômicas, demográficas, comportamentais e de saúde. Dor nas costas foi definida como qualquer dor ou desconforto em algum local das costas nos últimos 12 meses, seja na região cervical, torácica ou lombar. RESULTADOS: A prevalência de dor nas costas foi de 63,1% (IC95% 60,0 a 66,1), sendo a região lombar a mais referenciada (40%). Sexo feminino 1,24 (1,12 a 1,37) e percepção ruim de saúde (pOBJECTIVES: To identify the prevalence of spinal pain and possible prognostic factors in a representative sample of Pelotas, RS, Brazil. METHODS: Cross-sectional study evaluated 972 adults aged between 20 and 69 years, of both sexes, residents in a urban area. The questionnaire included socio-economic, demographics, behavioral and health-related questions. Spinal pain was defined as any pain or discomfort in the spine somewhere in the last 12 months, either in the cervical, thoracic or lumbar area. RESULTS: The prevalence of spinal pain was 63.1% (95% CI 60.0 to 66.1) being lower back the most prevalent condition (40%). Female gender 1.24 (1.12 to 1.37) and poor health status(p

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 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 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 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 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%.

To identify the prevalence of spinal pain and possible prognostic factors in a representative sample of Pelotas, RS, Brazil.Cross-sectional study evaluated 972 adults aged between 20 and 69 years, of both sexes, residents in a urban area. The questionnaire included socio-economic, demographics, behavioral and health-related questions. Spinal pain was defined as any pain or discomfort in the spine somewhere in the last 12 months, either in the cervical, thoracic or lumbar area.The prevalence of spinal pain was 63.1% (95% CI 60.0 to 66.1) being lower back the most prevalent condition (40%). Female gender 1.24 (1.12 to 1.37) and poor health status(p0.001) were the variables that remained associated with the presence of spinal pain in the final model.The prevalence of back pain is important as it is associated with activity limitation and with health care utilization.