Localização de descargas parciais em transformadores de potência por meio de sensores piezelétricos de baixo custo e sistemas inteligentes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Localização de descargas parciais em transformadores de potência por meio de sensores piezelétricos de baixo custo e sistemas inteligentes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Two methods for voltage sag source location

This paper presents and compares two approaches to estimate the origin (upstream or downstream) of voltage sag registered in distribution substations. The first approach is based on the application of a single rule dealing with features extracted from the impedances during the fault whereas the second method exploit the variability of waveforms from an statistical point of view. Both approaches have been tested with voltage sags registered in distribution substations and advantages, drawbacks and comparative results are presented

Estimation of zero-sequence impedance of undergrounds cables for single-phase fault location in distribution systems with electric arc

This paper focus on the problem of locating single-phase faults in mixed distribution electric systems, with overhead lines and underground cables, using voltage and current measurements at the sending-end and sequence model of the network. Since calculating series impedance for underground cables is not as simple as in the case of overhead lines, the paper proposes a methodology to obtain an estimation of zero-sequence impedance of underground cables starting from previous single-faults occurred in the system, in which an electric arc occurred at the fault location. For this reason, the signal is previously pretreated to eliminate its peaks voltage and the analysis can be done working with a signal as close as a sinus wave as possible

Application for fault location in electrical power distribution systems

Fault location has been studied deeply for transmission lines due to its importance in power systems. Nowadays the problem of fault location on distribution systems is receiving special attention mainly because of the power quality regulations. In this context, this paper presents an application software developed in Matlabtrade that automatically calculates the location of a fault in a distribution power system, starting from voltages and currents measured at the line terminal and the model of the distribution power system data. The application is based on a N-ary tree structure, which is suitable to be used in this application due to the highly branched and the non- homogeneity nature of the distribution systems, and has been developed for single-phase, two-phase, two-phase-to-ground, and three-phase faults. The implemented application is tested by using fault data in a real electrical distribution power system

A hybrid method for sag source location in power network

The work presented in this paper belongs to the power quality knowledge area and deals with the voltage sags in power transmission and distribution systems. Propagating throughout the power network, voltage sags can cause plenty of problems for domestic and industrial loads that can financially cost a lot. To impose penalties to responsible party and to improve monitoring and mitigation strategies, sags must be located in the power network. With such a worthwhile objective, this paper comes up with a new method for associating a sag waveform with its origin in transmission and distribution networks. It solves this problem through developing hybrid methods which hire multiway principal component analysis (MPCA) as a dimension reduction tool. MPCA reexpresses sag waveforms in a new subspace just in a few scores. We train some well-known classifiers with these scores and exploit them for classification of future sags. The capabilities of the proposed method for dimension reduction and classification are examined using the real data gathered from three substations in Catalonia, Spain. The obtained classification rates certify the goodness and powerfulness of the developed hybrid methods as brand-new tools for sag classification

Nest location, clutch size and nest success in the Scarlet Ibis Eudocimus ruber

Breeding success and nest-site characteristics were studied during the 1996-1997 breeding season in a colony of Scarlet Ibises Eudocimus ruber in south-eastern Brazil to test the hypothesis that nest-site characteristics and clutch size affect nest success. Two nesting pulses produced young, the earlier being more successful. Predation accounted for most failures during the first pulse, wind destruction during the second. A third pulse with few nests produced no young. Adult Ibises abandoned nests when they lost sight of other incubating birds. Logistic regression analysis indicated that nest success during the first pulse was positively related to clutch size, number of nests in the nest tree and in the nearest tree, and negatively to the distance to the nearest neighbour. During the second pulse there were significant negative associations between success, nest height and distance to the fourth nearest nest, and a positive association between success and nest cover. The results agree with the 'selfish herd' hypothesis, indicating that nest aggregation may increase breeding success, but the nest-site characteristics affecting success can differ over the course of one breeding season.

Fault location in underground systems using artificial neural networks and PSCAD/EMTDC

The need for high reliability and environmental concerns are making the underground networks the most appropriate choice of energy distribution. However, like any other system, underground distribution systems are not free of failures. In this context, this work presents an approach to study underground systems using computational tools by integrating the software PSCAD/EMTDC with artificial neural networks to assist fault location in power distribution systems. Targeted benefits include greater accuracy and reduced repair time. The results presented here shows the feasibility of the proposed approach. © 2012 IEEE.

A retrospective analysis of patients referred for implant placement to a specialty clinic: indications, surgical procedures, and early failures

Purpose: This retrospective study analyzed the pool of patients referred for treatment with dental implants over a 3-year period in a referral specialty clinic. Materials and Methods: All patients receiving dental implants between 2002 and 2004 in the Department of Oral Surgery and Stomatology, University of Bern, were included in this retrospective study. Patients were analyzed according to age, gender, indications for implant therapy, location of implants, and type and length of implants placed. A cumulative logistic regression analysis was performed to identify and analyze potential risk factors for complications or failures. Results: A total of 1,206 patients received 1,817 dental implants. The group comprised 573 men and 633 women with a mean age of 55.2 years. Almost 60% of patients were age 50 or older. The most frequent indication for implant therapy was single-tooth replacement in the maxilla (522 implants or 28.7%). A total of 726 implants (40%) were inserted in the esthetically demanding region of the anterior maxilla. For 939 implants (51.7%), additional bone-augmentation procedures were required. Of these, ridge augmentation with guided bone regeneration was performed more frequently than sinus grafting. Thirteen complications leading to early failures were recorded, resulting in an early failure rate of 0.7%. The regression analysis failed to identify statistically significant failure etiologies for the variables assessed. Conclusions: From this study it can be concluded that patients referred to a specialty clinic for implant placement were more likely to be partially edentulous and over 50 years old. Single-tooth replacement was the most frequent indication (> 50%). Similarly, additional bone augmentation was indicated in more than 50% of cases. Adhering to strict patient selection criteria and a standardized surgical protocol, an early failure rate of 0.7% was experienced in this study population

Enhancing the trust of location acquisition systems for critical applications and location-based security services

This paper identifies a number of critical infrastructure applications that are reliant on location services from cooperative location technologies such as GPS and GSM. We show that these location technologies can be represented in a general location model, such that the model components can be used for vulnerability analysis. We perform a vulnerability analysis on these components of GSM and GPS location systems as well as a number of augmentations to these systems.