Navegando por Assunto "Descargas parciais"

Agora exibindo 1 - 10 de 10

Acesso aberto (Open Access)
Aplicação de método de reconstrução de sinais baseado em decomposição variacional de modos no processamento de sinais de descargas parciais
(Universidade Federal do Pará, 2024-09-23) ALMEIDA, Vanilze Vaz Monteiro de; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447
High-voltage equipment in electrical systems is subject to electrical insulation degradation, which promotes the evolution of partial discharge activity (PDs), a key factor in operational failures of these assets, resulting in significant losses. Therefore, the analysis of PD signals for accurate representation of operational conditions is essential, as it aids in making assertive decisions in predictive maintenance of equipment, as well as understanding their impacts. The procedure for acquiring PDs involves measurements using invasive or non-invasive devices, which show the occurrence of this phenomenon under field or laboratory operating conditions. However, this acquisition is subject to interference, leading to PD signals embedded in noise, which may arise from the electromagnetic nature of the equipment used or from external sources. This highlights the need to implement noise reduction and signal reconstruction techniques that ensure good representation of PDs, allowing for precise analysis by minimizing the loss of signal characteristics for further studies. Thus, in this work, a study was conducted on four noise reduction techniques for PD signals: Variational Mode Decomposition (VMD), Adaptive Filtering with Least Mean Squares algorithm (LMS), Wavelet Transform with Hard Thresholding (HTWT), and Wavelet Transform with Soft Thresholding (STWT), for reconstructing real PD signals obtained from measurements with High-Frequency Current Transformer (HFCT). The results from the signal filtering process were evaluated using metrics such as Root Mean Square Error (RMSE), Signal-to-Noise Ratio (SNR), and Correlation Coefficient (CC), demonstrating the importance of filtering methodology with the incorporation of VMD and the variation of parameters and filtering sequences established.
Acesso aberto (Open Access)
Descargas parciais em barras estatóricas de hidrogeradores: modelagem por guia de onda e análise de um acoplador
(Universidade Federal do Pará, 2009-10-23) KAWAKATSU, Williams Massayuki; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
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)
Detecção e localização de descargas parciais em transformadores de potência utilizando sinais acústicoas transitórios e o método GSPS
(Universidade Federal do Pará, 2015-01-29) ARAÚJO, José Weliton de Oliveira; FARIAS, Rubem Gonçalves; http://lattes.cnpq.br/3261608243924147; OLIVEIRA, Rodrigo Melo e Silva de; http://lattes.cnpq.br/4768904697900863
In this work, we develop a method for locating partial discharges (PDs), in power transformers, based on GPS (Global Positioning System) algorithm. For analyzing the structure, we implement a software in which the di erential equations that describe the propagation of acoustic waves are solved numerically by the Acoustic Finite-Di erence Time-Domain (AFDTD) method. The AFDTD computational domain is truncated by the CPML technique (Convolutional Perfectly Matched Layer). The obtained results are compared to estimates produced using electromagnetic waves generated by PDs.
Acesso aberto (Open Access)
Estudo comparativo de métodos de filtragem para medições não-invasivas de descargas parciais em sistemas de alta tensão: abordagens com diferentes filtros clássicos, adaptativo e transformada wavelet.
(Universidade Federal do Pará, 2024-11-06) SILVA, Adriel Brito da; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447; https://orcid.org/0000-0001-5079-4126
The Partial discharge (PD) phenomene occur in segmented manner in electrical insulation. Over time, these occurrences can evolve to a critical state, resulting in short circuits and significant damage to electrical equipment. PD detection and analysis are essential in the context of preventive maintenance, contributing to high availability rates of Electrical Power Systems (EPS). However, interference from various noise sources, such as other electrical equipment and electromagnetic phenomena, makes PD signal detection challenging. This work presents a comparative study of filtering and signal analysis methods in noninvasive measurements of partial discharges in real high voltage systems, using different classical filters and the Wavelet Transform (WT). The research evaluated the effectiveness of several filtering methods in noise reduction, providing better identification and characterization of PD signals. Classic filters such as Moving Average (MA), Butterworth (BW), Chebsyshev (Type I), SavitzkyGolay (SG) and adaptive filtering such as Least Mean Squares (LSM), in addition to techniques based on multiresolution wavelet decomposition, were implemented and compared to verify metrics such as Signal-to-Noise Ratio (SNR), Cross-Correlation (CC), Root Mean Square Error (RMSE), Kurtosis (K), and others, considering the preservation of the essential characteristics of PD signals. The results obtained demonstrated that filtering techniques are crucial for reducing noise effects, although more classical methods present limited efficiency when compared to those with adaptive capacity. The comparative analysis revealed critical points that, although they demonstrated restricted efficiency, contribute significantly to the improvement of electrical equipment monitoring methods.
Acesso aberto (Open Access)
O estudo da influência do ciclo de partidas e paradas no estator de geradores síncronos
(Universidade Federal do Pará, 2011-02-28) SANTOS, Renato Lelio da Silva; OLIVEIRA, Roberto Célio Limão de; http://lattes.cnpq.br/4497607460894318
The synchronous generators under different stops situations forced shutdown, shutdown by external conditions, scheduled for corrective and preventive maintenance. The different variations in temperature that undergoes a synchronous generator, exactly to its stator affects its isolation, which does not follow these constant changes, due to have a different coefficient of expansion. In the present work has identified a trend of progressive aging of the insulation of stator windings in their machines that suffer repetitive starting and stopping and staying with his reserve power off for several hours. The study was implemented in five synchronous generators Balbina hydroelectric of Eletrobras group, which presents such a problem. This study confirms for the tests of analysis of partial discharge of the synchronous generators performed periodically to diagnose problems in their stator windings, with different magnitudes and identify the thesis that machines that have larger magnitudes of partial discharges off in their stators are undergoing more amounts of starting and stopping and staying with the most hours with standby power off.
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)
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)
Transporte de ozônio em hidrogerador de 311 mva: modelagem fluidodinâmica tridimensional de máquina elétrica dos elementos finitos. através do método
(Universidade Federal do Pará, 2024-02-29) GIROTTO, Gustavo Gaspar; OLIVEIRA, Rodrigo Melo e Silva de; http://lattes.cnpq.br/4768904697900863
In this work, a three-dimensional numerical model of fluid dynamics is developed for a single 311 MVA power generator unit in a hydroelectric power plant using the finite element method. The goal is to study the ozone transport mechanisms within the enclosed structure of the electrical generator machine. Ozone is produced by partial discharges related to some faults in the stationary bars. To analyze the ozone transport from localized sources, a three-dimensional fluid dynamics model of an operational hydrogenerator is developed and presented for the first time. The model has a high level of geometric details. Additionally, a new proposal to simplify the modeling of radiators is implemented and validated. The modeled structure is based on an electrical machine from the Campos Novos hydrogenerator and consists of 378 coil-type stationary bars made of mica-coated copper and, externally, by a layer of semiconductor coating. Other parts are also represented, including the stationary core and air deflectors made of stainless steel, copper radiators, the rotor with its epoxy surface, and the floor and external walls made of concrete. In the fluid dynamics model, a finite element mesh is designed to represent the air regions inside the hydrogenerator and the surfaces of materials reacting with ozone (with their respective reaction rates), where air flow and ozone transport are modeled using the Navier-Stokes equations and the law of mass conservation. Partial discharge sources are represented by ozone sources with prismatic shapes, positioned on the surfaces of stationary bars. Ozone concentrations are calculated inside and around the generator machine. The rotor radius is 3.8075 m, and its rotation frequency is 200 RPM. The radial air velocity due to interpolar ventilation is also considered (2.2 m/s, as experimentally verified on-site). The radial velocity near the radiators is 3 m/s. It is concluded that the ozone transport profile is influenced by the source position on the stationary bars, so determining the source location is possible and depends on determining the local and global maximum ozone concentration areas on the radiators.
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%.