scholarly journals Effect of Floating Metallic Particles in Pre-Breakdown and Breakdown Characteristics of Oil Transformer under DC Voltage

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3669
Author(s):  
I. Made Yulistya Negara ◽  
Daniar Fahmi ◽  
Dimas Anton Asfani ◽  
I. G. N. Satriyadi Hernanda ◽  
Mochammad Wahyudi ◽  
...  
Keyword(s):  
Particle Size ◽  
Light Emission ◽  
Transformer Oil ◽  
Electrical Characteristics ◽  
Metallic Particles ◽  
Average Value ◽  
Corona Current ◽  
Voltage Stress ◽  
Floating Particles ◽  
Peak Value

Contaminants in transformer oil insulation can float when meeting several conditions. Then, the presence of floating contaminants affects the electrical characteristics of oil insulation. Therefore, the pre-breakdown (corona) and breakdown characteristics due to metallic floating particles in transformer oil insulation would be investigated. This test used DC high voltage stress. A 56 Ω resistor was connected to the oscilloscope to detect the corona currents. The camera was used to capture the images of corona light emission. In addition, the electric field between the electrode and particles was simulated. The variables were the particle size, including its shape, and the distance between the particles and the grounded electrode. The experimental results show that the average value of corona inception and breakdown was inversely proportional to the size of floating particles. The peak value of corona current was directly proportional to the particle size. The lowest breakdown voltage was found when the particle was close to the electrode, but they were not in contact.

scholarly journals Green Light Emission ofZnxCd1-xSeNanocrystals Synthesized by One-Pot Method

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Shu-Ru Chung ◽  
Kuan-Wen Wang ◽  
Hong-Shuo Chen
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Light Emission ◽  
Green Light ◽  
Particle Size Effect ◽  
Partial Replacement ◽  
Face Centered Cubic ◽  
One Pot ◽  
Zn Content ◽  
High Emission

We present a facile one-pot synthesis to prepare ternaryZnxCd1-xSe(x= 0.2, 0.5, 0.8, and 1) nanocrystals (NCs) with high emission quantum yield (QY, 45~89%). The effect of Zn content (x) ofZnxCd1-xSeNCs on their physical properties is investigated. The NCs have a particle size of 3.2 nm and face centered cubic structure. However, the actual compositions of the NCs are Zn0.03Cd0.97Se, Zn0.11Cd0.89Se, and Zn0.38Cd0.62Se when Zn content is 0.2, 0.5, and 0.8, respectively. In terms of the optical properties, the emission wavelength shifts from 512 to 545 nm with increasing Zn content from 0 to 0.8 while the QY changes from 89 to 45, respectively. Partial replacement of Cd by Zn is beneficial to improve the QY of Zn0.2and Zn0.5NCs. The optical properties of ternary NCs are affected by compositional effect rather than particle size effect.

scholarly journals Spatial variability of particle size fractions of an Oxisol cultivated with conilon coffee

Revista CERES ◽  
2012 ◽  
Vol 59 (6) ◽  
pp. 867-872 ◽  
Author(s):  
Julião Soares de Souza Lima ◽  
Rone Batista de Oliveira ◽  
Samuel de Assis Silva
Keyword(s):  
Particle Size ◽  
Spatial Variability ◽  
Clay Fraction ◽  
Soil Samples ◽  
Landscape Configuration ◽  
Sand Fraction ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Average Value ◽  
Significant Difference

Information on the spatial distribution of particle size fractions is essential for use planning and management of soils. The aim of this work to was to study the spatial variability of particle size fractions of a Typic Hapludox cultivated with conilon coffee. The soil samples were collected at depths of 0-0.20 and 0.20-0.40 m in the coffee canopy projection, totaling 109 georeferentiated points. At the depth of 0.2-0.4 m the clay fraction showed average value significantly higher, while the sand fraction showed was higher in the depth of 0-0.20 m. The silt showed no significant difference between the two depths. The particle size fractions showed medium and high spatial variability. The levels of total sand and clay have positive and negative correlation, respectively, with the altitude of the sampling points, indicating the influence of landscape configuration.

Experimental Study on the Effect of Ultrasonic Cavitation on Pyrolysis Characteristics of Oil Shale

2013 ◽  
Vol 295-298 ◽  
pp. 3117-3123
Author(s):  
Hong Tian ◽  
Zheng Zhu Liao
Keyword(s):  
Weight Loss ◽  
Particle Size ◽  
Organic Matter ◽  
Oil Shale ◽  
Loss Rate ◽  
Ultrasonic Cavitation ◽  
Ultrasonic Frequency ◽  
Ultrasonic Power ◽  
Weight Loss Rate ◽  
Peak Value

In order to investigate the pyrolysis characteristics of oil shale under in the extreme conditions of high temperature and high pressure generated by the ultrasonic cavitation. The different particle size of oil shale is mixed with water in accordance with the volume ratio of 1:12, under in different ultrasonic frequency and different power, the ultrasonic radiation experiments and the thermogravimetric experiments of different samples have been done. The results show that the organic content of oil shale samples reduced after ultrasonic radiation, and the chemical reaction rate of the remaining organic matter become faster, and its reflected as the volatile separate out rate was accelerated and the changes of TG(Thermogravimetry) and DTG(Derivative Thermogravimetry) curves were steeper. Oil shale pyrolysis weight loss rate peak values and the organic matter decomposed percentage during the pyrolysis have the selective on the ultrasonic frequency, ultrasonic power and particle size of the oil shale. Oil shale pyrolysis weight loss rate peak value increased with decreasing of ultrasonic power, and the weight loss rate peak value corresponding to the peak temperature was increased with the increasing of ultrasonic frequency, and the weight loss rate peak value corresponding temperature decreased with particle size increasing of oil shale. We can draw the conclusion that the ultrasonic cavitation can decomposition organic matter of oil shale, then, we should in-depth research the ultrasonic refining shale oil.

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