1,720,954 research outputs found
The Effect of Controlling Stray and Disc Capacitance of Ceramic String Insulator in the Case of Clean and Contaminated Conditions
No full textAbstractDue to their flexibility against the tension force and the easiness of maintenance characteristics of overhead transmission line, one of the biggest problems when using ceramic string insulator is the non-uniform voltage distribution on each insulator disc that connected on the string. This paper analyzes the effect of controlling stray capacitance (Kcsc), disc capacitance (Kcdc) and contaminated pollution (Kccp). In this paper research study considerations, the Electricity Generating Authority of Thailand (EGAT) 115kV overhead transmission line power towers are simulated in EMTP/ATP drawing and the results were analyzed. As it was found that in the clean condition, when the constant (Kcsc) was conducted and adjustment when Kcsc value has low value (decreases), the string efficiency would be high value (increases) for instances Kcsc=0.01 string efficiency=99%, Kcsc=0.50 string efficiency=64%. When the constant (Kcdc) was adjusted; if Kcdc is low, the string efficiency will also be low for instances at Kcdc=0.01 string efficiency=33%, Kcdc=0.50 string efficiency=40%. Nevertheless, Kcdc adjustment utilizes the appropriate value gained from factory that the k=0, so the value will be 90% higher. As for the contaminated condition, when the constant (Kcsc) was adjusted as shown in Fig.11, if Kcsc value is low, the string efficiency will be high for instances Kcsc=0.01 string efficiency=99%, Kcsc=0.05 string efficiency=65%. When the constant (Kcdc) was adjusted; if Kcdc is low, the string efficiency will also be low for instances at Kcdc=0.01 string efficiency=17%, Kcdc=0.50 string efficiency=40%. Considering on Kccp, for example Kccp=0.01 string efficiency=82% Kccp=0.50 string efficiency=55%
The Investigation of Insulation Breakdown Strength for the Nano-composite Oxide Doped Epoxy Resin Insulator by Using Positive Impulse Voltage in Comparison with Negative Impulse Voltage
No full textAbstractThis article presents the nano-composite oxides in dielectric materials which are suitable for increasing the efficiency of the destruction of strength and durability against voltage. Tests were conducted to compare the characteristics and details of epoxy resin materials doped with nano zinc oxides by using positive and negative impulse standard voltage to test the destruction of specimen in order to make insulators more efficient and durable against the positive and the negative impulse voltage. This research also studied the abilities of nano-composite oxides to be used as electrical insulators - epoxy resin doped with zinc oxides nano-composite in ratios of 0, 5, 10, 15 and 20% by weight. After that, there were destruction tests by using impulse voltage at levels of 75, 90, 98, and 115 kV connected to the specimen's electrodes immersed in oil transformer by using each voltage level against specimen usage in each of the aforementioned ratios to investigate the damages on insulator surfaces and the number of breakdowns. In viewing damages on insulator surfaces, microscopes with magnification levels of 20-800X were used. From experimental results, it was found that regarding specimens used to doped an epoxy resin with zinc oxides nano-composite and each level of standard positive impulse voltage, in the first round of voltage feeding it was observed that the period of specimens surface destruction was higher than when negative impulse voltage were used, and the breakdown occurrences were also faster increasing than that the of standard negative impulse voltage were used. In conclusion, a 5% doped epoxy resin with nano-composite zinc oxides tested with negative impulse voltage has better properties as an insulator than other samples in ratios of 0, 10, 15, and 20%, respectively, as the 5% ratio has a breakdown occurrences also happened later with smaller periods of insulator surface destruction in the first round of voltage feeding than the other cases
Reduction of Power Loss from Corona Phenomena in High Voltage Transmission Line 115 and 230 kV
No full textAbstractThe Power Loss from Corona Phenomena in High Voltage Transmission Line 115 and 230 kV were studied the effects of various elements that affect the power loss from corona in high voltage transmission line between Khon Kaen and Nakhon Ratchasima and the method to reduce power loss due to corona. This paper clarifies Peek's and Peterson's formula by utilizing Matlab program with the effect from different variables including conductor spacing, conductor radius and a system voltage. The Peterson's formula was suitable for the two systems than that of Peek's formula under the condition of phase voltage to corona inception voltage ratio. In the 115 kV system uses 795 MCM ACSR conductor with 1.447 cm radius and the spacing was 320 cm could generate a less power loss, and the 230 kV system uses 1272 MCM ACSR conductor with 1.75 radius, the spacing was 500 cm could generate a less power loss. When simulated to solve the conductor radius and the spacing that would have the less power loss. In 115 kV system, the suitable was 1.36 cm radius and 266 cm spacing and in 230 kV system the suitable was 0.85 cm radius and 660 cm. It therefore could reduce power loss by selecting the conductor radius and the conductor space increasing or protecting the system from the lightning
The Comparison Characteristics of Investigation Breakdown Voltage of Long Flash over Arrestor (LFA) with Different Gaps Space by Using Positive and Negative Impulse Voltage
No full textAbstractThis paper presents the investigation and compares the ring components characteristics of long flashover arrestor (LFA) multi-gap and single gap. There are two cases in this work: (i) the gap ring for the multi-gap with various spacing of 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0 cm with diameter of 2.20 cm, and (ii) the gap ring for the single gap with various gap spaces to maximum length of break down. The standard positive and negative impulse voltage was applied from 9 – 150 kV. The results show that LFA with the same breakdown voltage and different gap spaces had the different flashover lengths. The flash length of LFA multi-gap with gap space of 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0 cm under positive and negative impulse is almost the same value and lower than the LFA single gap. The flash length of LFA gap of 0.5 cm under the positive impulse voltage is longer than under the condition of the negative impulse voltage average about 1.5 cm. The flash length of single gap is equally with the voltage level 9-72 kV. At the positive voltage over 72 kV that the flash of LFA gab 0.5 cm is longer than LFA single gap
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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