Navegando por Assunto "Hidrogeradores"

Agora exibindo 1 - 7 de 7

Acesso aberto (Open Access)
Análise multifísica e experimentos em sensores ópticos usados na medição de temperatura em rotores de hidrogeradores
(Universidade Federal do Pará, 2017-04-12) LEITE, Reinaldo Corrêa; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
Fiber Bragg gratings (FBGs) offer new possibilities to monitor accurately the rotor temperature. Dozens of sensors can be mounted in series in a single fiber and used to measure the temperature in several points of the rotor winding. Such sensors installed directly on the rotor winding surface are thermally isolated from the cooling air by a silicone layer. Because of the temperature gradient in this structure, the sensor is exposed to thermo-mechanical stresses and therefore can be deformed. Since the FBG probes are sensitive to both temperature and strain, the knowledge of each effect separately is necessary to ensure that the temperature readings are not affected by strain. Experimental results obtained in rotor winding mockup tests with thermistors and FBG sensors show that the temperature readings by the FBG are 4.5°C above the temperature defined by the thermistors which were used as references. Multi-physics simulations were carried out to calculate the strain and temperature in the FBG assembly. The theoretical and experimental results are in a good agreement and show that the temperature gradient across the FBG sensor assembly is sufficient to cause a strain that induces an axial stress in the FBG sensor causing an error in the temperature reading.
Acesso aberto (Open Access)
Caracterização de padrões de descargas parciais em hidrogeradores utilizando técnicas de inteligência computacional
(Universidade Federal do Pará, 2015-09-24) ALVES, Medillin Pereira; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447
This master's thesis presents the experiments with applications of computational intelligence techniques for the characterization of partial discharges in hydrogenerators. The classification of the partial discharge contributes to a prior analysis problems and allows predictive maintenance on machinery, reducing the possibility of failures in them. Data were collected online mode (operation machine) in the Tucuruí Hydroelectric Power Plant, observed the internal discharge standards, delamination and between bars. The IMA-DP software, developed in partnership with Eletronorte and Cepel, allowed these data were measured and recorded quickly, and organized through PRPD maps (Phase resolved Partial Discharges). Binarization techniques, ANOVA (Analisys of Variance), ICA (Independent Component Analysis) and PCA (Principal Component Analysis) were applied to the signals to adapt them to the use of computational intelligence techniques. The study was developed in IPython environment using scikit-learn library, which has efficient intelligence algorithms. The experiments were performed making use of techniques: KNN (K-Nearest Neighbors), Random Forest and MVS (Support Vector Machines). Such techniques showed good results with the experiments, highlighting those obtained for MVS that showed the best results, achieving an accuracy of 96.07%, due possess selection mechanisms of the main variables during the training process.
Acesso aberto (Open Access)
Desenvolvimento de sensores eletromagnéticos para medição de descargas parciais nos enrolamentos estatóricos de hidrogeradores
(Universidade Federal do Pará, 2016-04-14) BRASIL, Fernando de Souza; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
Stops machines unplanned caused by faults in the electrical insulation of the power electric system equipment is a big problem, because account for high losses to plan and undertake performance indicators due long stop period generating unit necessary for the generation function restoration. In order to solve this problem, many researchers and scholars in the field of large rotating machines found that these failures were often related to the increased level of partial discharges (PD) of electrical insulation of the machine. Occurrences of PDs in insulating systems of high voltage equipment are symptoms of weakness in their dielectric withstand, whose evolution can cause serious consequences for the equipment. The PDs can be detected by measuring quantities associated with current pulses, radio frequency signals (electromagnetic waves), acoustic signals, among others. Among these methods the detection of electromagnetic waves radiated by PDs are proving to be a reliable technique to follow the default process of evolution. In comparison with other techniques such as the detection method based on capacitive couplers (conventional method), the use of electromagnetic broadband sensors is not invasive to isolation. In this way, this paper aims to show the evaluation of three different electromagnetic sensors of Ultra High Frequency (UHF) designed to be installed in hydrogenerators. The sensors used in the experiments are: microstrip directional coupler, loop antenna and log-periodic antenna. The sensors were evaluated by high-voltage tests to measure partial discharges which were evaluated all kids of discharges found in hydrogenerators, like internal discharges, delaminations, slot discharge, bar-bar and surface discharges, and through the accelarated aging test. The results obtained in the laboratory demonstrated that the directional coupler showed a high sensibility to all types os simulated discharges which results were validated by log-periodic antenna, and the loop antenna showed a low sensibility. The results also demonstrated that is possible to identify discharges through the UHF characteristics. The evolution of the PDs levels were evaluated through the directional coupler during the accelarated aging test, it was possible to observe the appearance of two types of discharges, delaminations and corona, the results were similar to those measured by the capacitive coupler.
Acesso aberto (Open Access)
Estudo experimental de técnicas de medição de descargas parciais nos enrolamentos estatóricos de hidrogeradores
(Universidade Federal do Pará, 2013-07-10) BRASIL, Fernando de Souza; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
This paper aims at analyzing experimental techniques for partial discharges measuring in the stator windings of hydrogenerators. To reach the goal, first proposed a study of the literature on how the structure of the stator windings, with an emphasis on electrical insulation, as well as the concepts of partial discharges and techniques used for measuring in hydrogenerators. It was then mounted in a laboratory arrangement for studying techniques for measuring partial discharges in the stator winding using six different couplers, four conventional capacitive couplers 80, 220, 500 and 1000 pF, and two experimental systems, an antenna, ribbon coaxial cable and RG 58, bare used with the antenna function. The evaluation of the sensitivity of these six systems has been divided in two steps: first were analyzed the responses of couplers applying a known calibration signal, and then analyzed the response of the same high voltage during testing. For application of a known signal calibration the capacitive couplers showed greater sensitivity than antenna and coaxial cable. Already during the response tests showed that the High Voltage sensitivity of the antenna tape is larger than the conventional method of measuring partial discharges in hydro using capacitive couplers 80 and 220 pF. The results obtained in the laboratory showed that the measurement of partial discharges through the antenna tape can be performed satisfactorily in the evaluation of the operating condition of the stator windings of hydro, without either significant loss of sensitivity information or the quantification of the phenomenon.
Acesso aberto (Open Access)
Experimentos de mineração de dados aplicados a sistemas scada de usinas hidrelétricas
(Universidade Federal do Pará, 2012-04-13) OHANA, Ivaldo; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
The current model of the Brazilian electric sector allows equal terms to all actors and reduces the role of the State in this sector. This model forces the electrical utilities to improve the quality of their products and, as a prerequisite for this purpose, they should make more effective use of the enormous amount of operational data that are stored in databases, acquired from the operation of their electrical systems which use the hydroelectric power plants as their main source of energy generation. One of the main tools for managing the operation of these plants are the Supervisory Control and Data Acquisition systems (SCADA). Thus, the large amount of data stored in databases by SCADA systems, certainly containing relevant information, should be treated to discover relationships and patterns that would help in the understanding of many important operational aspects as well as in the evaluation of operational performance of the electric power systems. The process of Knowledge Discovery in Database (KDD) is the process of identification of patterns in large data sets, that are valid, new, and useful to improve the understanding of a problem or a decision-making procedure. Data Mining is the step within KDD that extracts useful information from large databases. In this scenario, the present study objective is to perform data mining experiments on data generated by power plants SCADA systems, to produce relevant information to assist in planning, operation, maintenance and security of hydro power plants and also contribute to the implementation of the culture of using data mining techniques applied to these plants.
Acesso aberto (Open Access)
Sistema para detecção, localização e monitoramento de descargas parciais em estatores de hidrogeradores
(Universidade Federal do Pará, 2015-11-30) VILHENA, Paulo Roberto Moutinho de; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
Stops machines unplanned caused by faults in the electrical insulation of the power electric system equipment is a big problem, because account for high losses to plan and undertake performance indicators due long stop period generating unit necessary for the generation function restoration. In order to solve this problem, many researchers and scholars in the field of large rotating machines found that these failures were often related to the increased level of partial discharges (PDs) of electrical insulation of the machine. Occurrences of PDs in insulating systems of high voltage equipment are symptoms of weakness in their dielectric withstand, whose evolution can cause serious consequences for the equipment. Because of these consequences, the evaluation of the operating status of the stator winding through the on line PDs measurement system proposed in this thesis presents strategies to increase the reliability of the measurements. As PDs sensor, it has been suggested to use electromagnetic microstrip directional coupler can detect the signal with the highest bandwidth in the UHF band, compared to existing traditional sensors. The development and implementation of virtual simulator PDs caused by the need of having Examples of signals that allow testing some PDs signal processing techniques. The main result of this thesis is the DP measurement system (called SIM_DP) including sensor, data acquisition system, PDs signal processing software and analysis of results. By studying the propagation of the signal in a stator bar was possible to develop a new methodology based on spectral analysis for PDs location. Through the structure created in the laboratory, it was possible to validate the SIM_DP system which favored the review of the PDs phenomenon. Finally actual data were analyzed for DP measurements in the field and correlation of PDs with mechanical vibration. The results of the work contributed to a more accurate diagnosis of the phenomenon. The results of the thesis have been improved in laboratory and field producing new: implementation of new laboratory tests as Voltage Endurance Test (VET), new non-invasive sensors such as antennas capable of measuring partial discharges and new techniques used in the analysis and diagnosis of related DP phenomena which will be presented in future work.
Acesso aberto (Open Access)
Uso de técnicas de mineração de dados para a extração de indicação de falha na operação de hidrogeradores a partir de medidas de descargas parciais
(Universidade Federal do Pará, 2016-06-17) PARDAUIL, Ana Carolina Neves; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
By studies conducted by CIGRE in 2009, it was found that the main source of hydro generator failures is correlated to the machine electrical insulation. Due to this fact, monitoring the stator winding conditions became an important supervising procedure. A very used practice to accomplish this supervision is through the measurement and analysis of partial discharges (PDs), being this practice one of the most effective and secure methods for analysis of generator stator insulation. However, although PDs have well-defined standards, it is not trivial to classify the obtained PDs signals in these patterns, mainly due to the large number and variety of PDs occurrences. Today, the significant increase in the amount of PDs data available was due to improvements in equipment and software for PDs monitoring, as for example the system IMA-DP, which has contributed to better planned and more frequent measurement campaigns. So, this work proposes the use of an intelligent tool to facilitate the process of identification and diagnosis of partial discharges, based on data mining techniques using decision trees (DT), which is a solution for analyzing large amount of data. In the specific case presented in this dissertation it was used 2,435 measurements obtained for phase A of a hydro generator of the Tucurui Hydro Plant, which was essential to validate the proposed method, because they represent real data obtained from the Hydro Plant operation. A hybrid approach (supervised/unsupervised) was used to identify and rank PDs patterns among the well-known forms of DPs. A fast and very satisfactory PDs classification procedure was achieved, especially when converting data from statistical maps into amplitude histograms, thus, obtaining well-defined clusters and a created decision tree that achieved global indices of accuracy above 98%.