Artigos em Revistas

The measurement and analysis of partial discharges (PD) are like medical examinations, such as Electrocardiogram (ECG), in which there are preestablished criteria. However, each patient will present his particularities that will not necessarily imply his condemnation. The consolidated method for PD processing has high qualifications in the statistical analysis of insulation status of electric generators. However, although the IEEE 1434 standard has well-established standards, it will not always be simple to classify signals obtained in the measurement of the hydro generator coupler due to variations in the same type of PD incidence that may occur as a result of the uniqueness of each machine subject to staff evaluation. In order to streamline the machine diagnostic process, a tool is suggested in this article that will provide this signal classification feature. These measurements will be established in groups that represent each known form of partial discharge established by the literature. It was combined with supervised and unsupervised techniques to create a hybrid method that identified the patterns and classified the measurement signals, with a high degree of precision. This paper proposes the use of data-mining techniques based on clustering to group the characteristic patterns of PD in hydro generators, defined in standards. Then, random forest decision trees were trained to classify cases from new measurements. A comparative analysis was performed among eight clustering algorithms and random forest for choosing which is the superior combination to make a better classification of the equipment diagnosis. R2 was used for assessing the data trend.

ANA C. N. PARDAUIL, THIAGO P. NASCIMENTO, MARCELO R. S. SIQUEIRA, UBIRATAN H. BEZERRA, WERBESTON D. OLIVEIRA

Brazil has started an energy transition process through more efficient electric motors. The new legislation determining the IE3 Class as the minimum efficiency level in commercial electric motors became valid in August 2019. Currently, four induction motor classes are defined by the IEC 60034-30-1, with the IE4 class being the most efficient, and in the same way, proposals to achieve IE5 efficiency class are available in the market. Considering the upcoming new technologies, it is necessary to know the impact of power systems disturbances in IM's in view of future substitutions. This paper presents a detailed analysis of the impact of different percentages of under and over voltage unbalances on the temperature and performance of electric motors classes IE2, IE3 and IE4. Results show that the IE4 hybrid motor presents non-linear characteristics, being observed this motor shows less dependence on voltage variation, mainly undervoltage unbalance. An analysis of how this phenomenon impacts on the current harmonic distortions in the induction motors operation is also developed through Spearman's correlation matrices. Finally, models that represent the temperature increase of each motor with different voltage unbalance conditions are presented.

JONATHAN MUÑOZ TABORA, MARIA EMÍLIA DE LIMA TOSTES, EDSON ORTIZ DE MATOS, UBIRATAN HOLANDA BEZERRA, THIAGO MOTA SOARES, BRUNO SANTANA DE ALBUQUERQUE

This paper presents a novel analysis methodology to detect degradation in electrical contacts, with the main goal of implanting a predictive maintenance procedure for sectionalizing switches, circuit breakers, and current transformers in bays of electric transmission and distribution substations. The main feature of the proposed methodology is that it will produce a predictive failure indication for the system under operation, based on the spectral analysis of the load current that is flowing through the bay’s components, using a defined relationship similar to the signal-to-noise ratio (SNR) used in data communication. A highlight of using the proposed methodology is that it is not necessary to make new investments in measurement devices, as the already-existing oscillography measurement infrastructure is enough. By implementing the diagnostic system proposed here, electrical utilities will have a modern tool for monitoring their electrical installations, supporting the implementation of new predictive maintenance functions typical of the current electrical smart grid scenario. Here, we present the preliminary results obtained by the application of the proposed technique using real data acquired from a 230 kV electrical substation, which indicate the effectiveness of the proposed diagnostic procedure.

FÁBIO VINICIUS VIEIRA BEZERRA, GERVÁSIO PROTÁSIO SANTOS CAVALCANTE, FABRÍCIO JOSE BRITO BARROS, MARIA EMÍLIA LIMA TOSTES, UBIRATAN HOLANDA BEZERRA

Global energy systems are undergoing a transition process towards renewable energy and energy efficiency practices. Induction motors play an important role in this energy transformation process since they are widely used as industrial loads, representing more than 53% of global energy consumption. With more countries adopting minimum energy performance standards through more efficient induction motors, comparisons between these new technologies in the presence of electrical disturbances must be systematically evaluated before adopting a substitution policy in the industry. To this end, this work presents a comparative analysis of the impact of harmonic voltages on the performance and temperature rise of electric motors classes IE2, IE3 and IE4 in the same operational conditions in view of future substitutions. The results show that under ideal operating conditions the IE4 class permanent magnet motor has better performance in terms of consumption and temperature, however presenting non-linear characteristics. In the presence of voltage harmonics, this scenario changes completely according to the harmonic content. Finally, aiming to analyze the harmonics influence in the motor temperature rise a statistical analysis by means of Spearman correlation matrices is presented.

JONATHAN MUÑOZ TABORA, MARIA EMÍLIA DE LIMA TOSTES, EDSON ORTIZ DE MATOS, THIAGO MOTA SOARES, UBIRATAN HOLANDA BEZERRA

The purpose of this article is to develop a methodology to apply to multi-objective optimization algorithms aimed at energy efficiency in buildings, considering aspects such as incremental cost, energy consumption, greenhouse gas emissions and energy efficiency levels of lighting and air conditioning system, according to the mandatory technical regulation in public buildings in Brazil. Presenting a solution to assist in the decision making of engineers, architects or building managers for the optimal arrangements’ choice for lighting and air conditioning equipment, considering each built environment and project profile. For the validation process, a basic building was created with 15 rooms spread over three floors, according to the most common construction parameters in the North of Brazil. First, different combinations of objective-function candidates were investigated to compose the multi-objective algorithm fitness function, analyzing its performance in two central scenarios: (1) adding some “baits” in air conditioning equipment files, and (2) without this inclusion. Thus, it was found that considering only three objective functions—incremental cost, energy consumption and the air conditioning energy efficiency coefficient—it is possible to get optimal non-dominated solutions in both scenarios, thus highlighting the robustness of the proposed methodology.

SUZANE A. MONTEIRO, FLÁVIA P. MONTEIRO, MARIA E. L. TOSTES, CARMINDA M. CARVALHO

Assessing the transient behavior of electric power transmission/distribution systems, when they are subjected to major disturbances such as lightning discharges, is an essential procedure to ensure the operational security of these systems, in order to supply good quality power to all consumers. Electromagnetic transient studies are routinely performed in the planning and operation phases of these systems, by using world widely known computer programs, among which stands out the Alternative Transient Program (ATP), via its graphical interface ATPDraw. However, preparing files for running case studies by using ATPDraw can become a time-consuming and human error-prone task. To overcome this drawback, this paper presents a toolbox for automatic generation and execution of Alternative Transient Program input files based on information directly obtained from technical databases of distribution utilities. This toolbox aims to reduce modeling time and susceptibility to human errors in the process of describing the grid in the software input file, which constitute the biggest obstacles to the extensive use of this program in real electric transmission/distribution networks. For the toolbox validation, a comparison was made between the input file generated by the ATPDraw auxiliary graphic interface and the file generated by the proposed toolbox by using the IEEE 13-bus and IEEE 34-bus test feeders. Besides that, the simulation results of both feeders for both softwares were compared, so that the correct operation of the Alternative Transient Program automatic case creator and executor proposed in this article were proved. In addition, the automatic generation of ATP cases for larger grids is exemplified with the IEEE 123-bus test feeder.

JOÃO RODRIGO DA SILVA MUNIZ, GABRIEL VIANNA SOARES ROCHA, RAPHAEL PABLO DE SOUZA BARRADAS, IGOR MEIRELES DE ARAÚJO, DANIEL DE SOUZA AVELAR DA COSTA, UBIRATAN HOLANDA BEZERRA

Metodologias com abordagens diferenciadas que auxiliem o ensino e a aprendizagem em sala de aula têm sido muito estudadas, como a utilização da robótica educacional, laboratórios virtuais e dispositivos físicos que são ferramentas educacionais que atualmente estão se destacando quando se trata de novas propostas metodológicas para o ensino de Ciências e Matemática. Este trabalho investigou a utilização de um recurso para fins educativos por meio da plataforma BBC Micro:bit, como forma de engajar, motivar e promover o letramento computacional e científico dos estudantes dentro de uma cultura maker. A Aprendizagem Baseada em Projeto (PBL) e a interdisciplinaridade de forma integrada pelas disciplinas de Ciências, Tecnologias, Engenharia, Artes e Matemática (STEAM), por meio da metodologia STEAM, foram utilizadas nesta pesquisa. Foi elaborada uma oficina com o uso do Micro:bit, aplicada aos estudantes do primeiro ano do curso técnico em Informática, modalidade ensino médio regular da EETEPA Dr. Celso Malcher. Observou-se a partir dos resultados analisados o Micro:bit pode ser utilizado como ferramenta metodológica para ensinar os conteúdos vistos em sala de aula, principalmente quando utiliza-se a PBL e a metodologia STEAM de forma integrada.

MÁRCIA CRISTINA PALHETA ALBUQUERQUE, WELLINGTON DA SILVA FONSECA, DAVID GENTIL DE OLIVEIRA, RAFAEL DE CASTRO SOUSA

Metodologias com abordagens diferenciadas que auxiliem o ensino e a aprendizagem em sala de aula têm sido muito estudadas, como a utilização da robótica educacional, laboratórios virtuais e dispositivos físicos que são ferramentas educacionais que atualmente estão se destacando quando se trata de novas propostas metodológicas para o ensino de Ciências e Matemática. Este trabalho investigou a utilização de um recurso para fins educativos por meio da plataforma BBC Micro:bit, como forma de engajar, motivar e promover o letramento computacional e científico dos estudantes dentro de uma cultura maker. A Aprendizagem Baseada em Projeto (PBL) e a interdisciplinaridade de forma integrada pelas disciplinas de Ciências, Tecnologias, Engenharia, Artes e Matemática (STEAM), por meio da metodologia STEAM, foram utilizadas nesta pesquisa. Foi elaborada uma oficina com o uso do Micro:bit, aplicada aos estudantes do primeiro ano do curso técnico em Informática, modalidade ensino médio regular da EETEPA Dr. Celso Malcher. Observou-se a partir dos resultados analisados o Micro:bit pode ser utilizado como ferramenta metodológica para ensinar os conteúdos vistos em sala de aula, principalmente quando utiliza-se a PBL e a metodologia STEAM de forma integrada.

MÁRCIA CRISTINA PALHETA ALBUQUERQUE, WELLINGTON DA SILVA FONSECA, DAVID GENTIL DE OLIVEIRA, RAFAEL DE CASTRO SOUSA

Direct lightning discharges in overhead distribution networks invariably cause serious insulation damage, frequently leading to the electric system’s partial or total shutdown. Installing lightning arresters can be very effective, and it is commonly used to minimize this problem; however, considering that typically, electric distribution grids exhibit a very large number of electrical nodes, the massive use of lightning arresters may not be economically viable. In this way, this article proposes a methodology for allocating lightning arresters that can significantly reduce the number of lightning arresters installed, but at the same time maintaining an adequate protection level for the distribution grid. The proposed methodology, named Direct Discharge Crossing (DDC), analyzes the network criticality based on two main factors, which are the overvoltage magnitudes and the number of flashovers provoked by lightning discharges, and defines a feeder lightning performance function that is used to indicate the recommended location for lightning arresters’ installation. The simulation studies are accomplished using the IEEE 34 bus distribution grid and ATP software to demonstrate the efficacy of the proposed solution, which is confirmed by the results presented.

RAPHAEL PABLO DE SOUZA BARRADAS, GABRIEL VIANNA SOARES ROCHA, JOÃO RODRIGO SILVA MUNIZ, UBIRATAN HOLANDA BEZERRA, MARCUS VINÍCIUS ALVES NUNES, JUCILENO SILVA E SILVA

Currently, for analyzing harmonic impacts on voltage at a point of interest, due to multiple nonlinear loads, the literature recommends carrying out simultaneous and synchronized measurement campaigns in all suspicious points with the use of high cost energy quality analyzers that are usually not available at the customers’ facilities and very often also not at the electric utilities. To overcome this drawback this paper proposes a method of assessing the harmonic impact due to multiple nonlinear loads on the total voltage harmonic distortion using only the load current true RMS values which are already available in all customers’ installations. The proposed methodology is based on Regression Tree technique using the Permutation Importance indicator which is validated in two case studies using two different electrical systems. The first case study is to ratify the use of Permutation Importance to measure the impact factor of each nonlinear load in a controlled scenario, the IEEE-13 bus test system, using ATP simulation (Alternative Transient Program). The second is to apply the methodology to a real system, an Advanced Measurement Infrastructure System (AMI) implanted on a campus of a Brazilian University, using low cost meters with only true RMS current measurements. The results achieved demonstrated the feasibility of applying the proposed methodology in real electric systems without the need for additional investments in high-cost energy quality analyzers.

FLÁVIA P. MONTEIRO, SUZANE A. MONTEIRO, MARIA E. TOSTES MARIA E. TOSTES, UBIRATAN H. BEZERRA