1,720,959 research outputs found
Frequency Dielectric Spectroscopy and Dissipation Factor Measurements during Thermal Cycles on Different Types of MV Cable Joints
Full text linkResults of periodic measurements of Dissipation Factor (DF) and Frequency Dielectric Spectroscopy (FDS) on Medium Voltage (MV) cables during thermal cycles, are reported and discussed in this paper. Twelve cables equipped with different types of joints were connected together to form a ring in short-circuit. The ring was energized at rated voltage and current. Temperature cycles with a period of one day (11 hours of heating) were applied by controlling the current. Periodically, each cable was tested separately using both DF and FDS techniques to monitor the ageing progression. This paper focuses on the experimental results obtained testing six new cables provided by different types of new joints while the other six coming from the field, are not considered here. Results obtained testing the six new cables indicate that FDS evaluation is a reliable tool to distinguish the aging progression of the insulation from the seasonal and reversible changes while DF values recorded at different voltage levels show a non-regular behavior particularly in XLPE cables. These results clearly suggest that the systematic use of FDS in condition assessment of underground cables can provide more information on the ageing progression than the traditional DF measurements
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
DIAGNOSTIC TECHNIQUES OF MV CABLE JOINTS UNDER DIFFERENT ENVIRONMENTAL CONDITIONS
Full text linkThe article reports the results and the advances of the experimentation in progress at the RSE laboratories for a diagnostic analysis of the causes of failures that affect MV cable joints, especially during the summer periods. To this purpose two different ad hoc experimental set-ups, consisting of cables equipped with different types of joints to form a ring in short-circuit, have been realized. The rings, energized at rated voltage, are loaded with current to reproduce the daily load variation typical of a MV cable network. The first set-up simulated the reduced thermal conductivity of the soil during summer periods and the second, now under test, allows to simulate, in a controlled way, the presence of rain, even of considerable intensity
Frequency dielectric spectroscopy and an innovative optical sensor to assess oil-paper degradation
No full textIn this paper, frequency dielectric spectroscopy (FDS) and an innovative optical sensor for the detection of 2-furaldehyde (2-FAL) are used to check the degree of ageing of differently processed oil-paper specimens when exposed to thermal stress. The analysis of the trend of moisture content and of 2-FAL concentrations confirms the influence of drying pre-Treatment of the specimens on their ageing conditions. FDS elucidated the nature of the drying process of the specimens and the optical sensor correctly assesses a lower 2-FAL production for the vapour phase dried specimens during thermal exposure
PARTIAL DISCHARGE INFERENCE BY AN ADVANCED SYSTEM: ANALYSIS OF ON-LINE MEASUREMENT PERFORMED ON HYDROGENERATORS
No full textA new system aimed at performing partial discharge measurements and condition assessment on electrical apparatus is presented. It is able to separate the conventional phase resolved partial discharge pattern into a series of sub-patterns, each of them containing partial discharge data generated by a single kind of defect, which makes easier identification of the source generating partial discharges. Application of the system to partial discharge data recorded on an hydrogenerator is reported to support its effectiveness
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Frequency Response Analysis of Power Transformers by Means of Fuzzy Tools
No full textA novel Fuzzy algorithm for the automatic analysis of frequency response of power transformers is described in this paper. It relies on the values of two parameters able to quantify the difference between the present and a reference frequency response, over three frequency ranges. These ranges are associated with different defect types, i.e., short circuits between turns, radial and axial displacements. Training examples obtained mainly from experimental results have been used to select the different ranges. Fuzzy-Logic has been adopted to reflect the uncertainty in the analysis of the differences between the two curves in the defect-identification results. Practical applications are also discussed to show the efficiency of the proposed diagnostic method
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