Viviane K. Asfora

A fuzzy system for detection of incipient fault in power transformers based on gas-in-oil analysis

Dissolved gas analysis (DGA) is one of the most useful techniques do detect the incipient faults of power transformer. However, the identification of the faulted location by the traditional method is not always an easy task due to the variability of gas data and operational natures. This work aims to develop an intelligent system of preventive maintenance for automatically detecting incipient fault in power transformers through analysis of dissolved gases in transformer insulating oil by introducing the IEC 599 standard (International Electrotechnical Commission). The data used to model the system are taken from chromatographic analysis of CELPE (Electrical Company from Pernambuco). The results show a system with high accuracy when compared with other papers approaching the same problem. Moreover, the results also proved the ability of multiple incipient faults detection.

Multivariate treatment of LIBS data of prehistoric paintings

Laser-induced breakdown spectroscopy (LIBS) was employed in the study of two fragments of prehistoric rock wall paintings found at two Brazilian sites: in Piaui State (Toca Extrema II) and in Rio Grande do Norte State (Xique-Xique). A time-resolved echellebased LIBS system assembled in the laboratory (laser Nd:YAG, 1064 nm, 5.2 ns) was employed for spectral acquisition. Preliminary depth profile studies were carried out in surrogate samples of a multilayer painting on wood to determine the best energy for the laser pulse. For each fragment of wall painting, the depth profile composition was investigated by firing 8 successive laser shots at each of 16 locations (8 in the area of pigment and 8 in the area of substrate). It is demonstrated in this work that the use of multivariate techniques is compulsory due to the high complexity of the spectral data obtained from depth profile studies of the archaeological samples.

Dating of fossil human teeth and shells from Toca do Enoque site at Serra das Confusões National Park, Brazil

This work reports the dating of a fossil human tooth and shell found at the archaeological site Toca do Enoque located in Serra das Confusões National Park (Piauí, Brazil). Many prehistoric paintings have been found at this site. An archaeological excavation unearthed three sepulchers with human skeletons and some shells. Two Brazilian laboratories, in Ribeirão Preto (USP) and Recife (UFPE), independently performed Electron Spin Resonance (ESR) measurements to date the tooth and the shell and obtain the equivalent dose received by each sample. The laboratories determined similar ages for the tooth and the shell (~4.8 kyBP). The results agreed with C-14 dating of the shell and other samples (charcoal) collected in the same sepulcher. Therefore, this work provides a valid inter-comparison of results by two independent ESR-dating laboratories and between two dating methods; i.e., C-14 and ESR, showing the validity of ESR dating for this range of ages.

Evaluation of a LiF:Mg,Ti thermoluminescent ring dosimeter according to the IEC 62387:2012 Standards

This work shows results of type testing of a ring radiation dosimeter system under IEC 62387:2012. The personal dosimeter investigated in this work consists of a commercial one element plastic ring which contains an LiF:Mg,Ti thermoluminescent pellet. By applying requirements for statistical fluctuations and linearity, a minimum measurable dose in Hp(0.07) was established. Energy and angular dependence aided in determining energy correction factors and fading requirements were used to select the most appropriate preheat scheme. Type testing of passive radiation monitors was performed in the Radiation Metrology Laboratory (LMRI-DEN/UFPE) of the Federal University of Pernambuco and is a major step in Brazil for the independent evaluation of these dosimeters, currently not available in the country.

The performance of a multi guard ring (MGR) diode for clinical electron beams dosimetry

The dosimetric response of a multi guard ring structure (MGR) diode has been studied with clinical electron beam energies from 5 MeV to 15 MeV. The results showed that the MGR dose response is linear in the range of 5-320 cGy and presents reproducibility with variation coefficients less than 0.4%. The field output factors measured with the MGR agreed within 2% with those measured with an ionization chamber. This study evidences that this diode can be used for clinical electron beam dosimetry.

FERRAMENTA INTELIGENTE DE CLASSIFICAÇÃO DO DIAGNÓSTICO DE FALHAS INCIPIENTES EM TRANSFORMADORES DE POTÊNCIA IMERSOS EM ÓLEO

of Dissertation presented to UFPE as a partial fulfillment of the requirements for the degree of Master in Electrical Engineering. Intelligent Tool rating Incipient Fault Diagnosis in Power Transformers Immersed in Oil Agnaldo Magnum de Souza Silva February/2012 Supervisors: Milde Maria da Silva Lira, D. Sc.;Ronaldo Ribeiro Barbosa de Aquino, D. Sc. Area of Concentration: Energy Processing