scholarly journals Preparation of Three Types of Transformer Oil-Based Nanofluids and Comparative Study on the Effect of Nanoparticle Concentrations on Insulating Property of Transformer Oil

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Qi Wang ◽  
Muhammad Rafiq ◽  
Yuzhen Lv ◽  
Chengrong Li ◽  
Kai Yi
Keyword(s):  
Thermal Properties ◽  
Comparative Study ◽  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Transformer Oil ◽  
Standard Methods ◽  
Maximum Value ◽  
Negative Impulse ◽  
The Difference

Nanofluids have the potential to become the alternatives of conventional transformer oil for their exquisite electrical and thermal properties. Three kinds of nanoparticles with distinct conductivities, namely, nonconductive nanoparticle Al2O3, conductive nanoparticle Fe3O4, and semiconductive nanoparticle TiO2, with different concentrations from 5% to 40% w/v were selected and suspended into transformer oil to develop nanofluids. The lightening impulse breakdown strengths of the oil samples with and without nanoparticles were measured according to IEC standard methods. The positive impulse breakdown strength indicated that breakdown strength is first increased up to the maximum value at certain concentration and then starts decreasing. The results of negative impulse breakdown manifested that the breakdown voltages of nanofluids with different concentrations were less than the breakdown voltage of pure transformer oil. Different effect mechanisms of dielectric and conductive nanoparticles were also used to describe the difference among three prepared nanofluids.

scholarly journals Lightning Impulse Breakdown Voltage of Rice Bran Oil for Transformer Application

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5084
Author(s):  
Mardhiah Hayati Abdul Hamid ◽  
Mohd Taufiq Ishak ◽  
Nur Sabrina Suhaimi ◽  
Jaafar Adnan ◽  
Nazrul Fariq Makmor ◽  
...  
Keyword(s):  
Weibull Distribution ◽  
Electric Fields ◽  
Breakdown Voltage ◽  
Rice Bran ◽  
Rice Bran Oil ◽  
Transformer Oil ◽  
Uniform Field ◽  
Testing Methods ◽  
Lightning Impulse ◽  
The Difference

Transformer oil does not only serve as an insulating liquid, but also in removing heat from the windings and cores. Mineral oil (MO) has been widely used in transformers for more than 150 years. Recently, researchers have attempted to search for alternative insulating oils due to the possibility that MO will run out in the future together with the concern on fire safety and environmental pollution. Among the potential oils is rice bran oil (RBO). This work presents the studies of the lightning impulse (LI) of RBO behavior under various electric fields, gap distances and testing methods. The electrical performances of LI tests show that RBO and Palm Oil (PO) have lower LI breakdown voltage than MO under both uniform and non-uniform electric fields. However, the difference in LI breakdown voltages between RBO, PO and MO are slightly small which is less than 20%. In addition, there is no significant effect in the various testing methods under both uniform field and non-uniform field where the percentages of difference are less than 12% and 8% respectively. The data of LI breakdown voltage were statistically analysed to predict the withstand voltage and 50% breakdown voltage of oil samples by using Weibull distribution. The Weibull distribution of MO, PO and RBO has well fit with the fitting line. Finally, the relationship between LI voltages under a non-uniform field with various parameters of PO and RBO was obtained and proposed. From this work, it can be concluded that RBO shows promising results to be considered as an alternative to MO in transformer applications.

A Comparative Study of Mechanical Properties in Ion-Irradiated A12O3 and MgO·nAl203

1998 ◽  
Vol 540 ◽  
Author(s):  
K. Yasuda ◽  
C. Kinoshita ◽  
K. Izumi
Keyword(s):  
Mechanical Properties ◽  
Comparative Study ◽  
Lattice Constant ◽  
Point Defects ◽  
Recombination Rate ◽  
Radiation Hardening ◽  
Maximum Value ◽  
Plastic Hardening ◽  
Load Displacement ◽  
The Difference

AbstractWe have investigated radiation hardening in alumina (A1203), stoichiometric and nonstoichiometric spinel (MgO·nA1203: n= 1, 2.4) crystals at 300 K irradiated with 100 keV He+ ions by using a ultra-microhardness technique. Al203 shows a remarkable radiation hardening (35% increase in hardness) at a fluence of 5×1019 He+/m2 and saturates at 60 % of the maximum value at fluences higher than 8×1019 He+/m2. In spinel crystals, hardness increases monotonically with fluence, reaching to a saturation at a fluence of 1×1020He+/m2. Analyses of load- displacement curves indicate that both plastic and elastic hardening are responsible for the radiation hardening in A1203, and that plastic hardening is the main cause in MgO'nAl2O3. Microstructure observations and lattice constant measurements showed that point defects are mainly responsible for the radiation hardening in both A1203 and MgO·nAl2O3. The difference in the radiation hardening response is discussed in terms of the difference in recombination rate of point defects among the MgO-A1203 system ceramics.

Investigation on Voltage Breakdown of Natural Ester Oils Based-On Zno Nanofluids

2015 ◽  
Vol 1119 ◽  
pp. 175-178 ◽  
Author(s):  
Wittawat Saenkhumwong ◽  
Amnart Suksri
Keyword(s):  
Power System ◽  
Breakdown Voltage ◽  
Palm Oil ◽  
Breakdown Strength ◽  
Mineral Oil ◽  
Transformer Oil ◽  
Slow Process ◽  
Zno Nanofluids ◽  
Voltage Breakdown ◽  
Natural Ester

Transformer is one of the major component, which is the most important device in power system. Their lifetime depends upon liquid insulation that help transfer the heat out of its winding inside of transformer. Transformer oil uses mineral oil that is the most commonly used has very slow process on decomposition and non-biodegrade. This paper presents the investigation on breakdown voltage of two types of natural ester oils, including palm oil and soy bean based-on ZnO nanofluids. Nanofluids that use nanoparticles modified by use of surfactant that are suspended by process of sonication. Different fraction of nanoparticles were investigated from 0.1% - 0.5% by weight. The breakdown voltage were measured according to ASTM D877. The voltage breakdown strength increased significantly when nanoparticles were added in oils. The obtained results will enable transformer industry to develop liquid insulation dielectric for use in transformer in the future.

scholarly journals Effect Of Phenol Addition To Transformer Oil Breakdown Voltage

2020 ◽  
Vol 8 (2) ◽  
pp. 77-81
Author(s):  
Amelya Indah Pratiwi
Keyword(s):  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Transformer Oil ◽  
Insulating Oil ◽  
Transformer Insulation ◽  
Is Failure ◽  
Insulation Oil

The failure of transformer insulation often occurs due to various kinds of things, one of which is failure in the oil isolation caused by the condition of oil that has been dirty or has been contaminated with other particles in the transformer. Phenol is a chemical that can purify or cleanse particles or impurities that are in used transformer oil, so that it can increase the breakdown stress on used insulation oil. Phenol contains acid which can attract particles and impurities in the transformer oil which results in a decrease in the breakdown strength of the insulating oil. The results of testing of used isolation oil by adding phenol as much as 10, 15 and 20 ml showed an increase in the value of breakdown voltage with a distance of 2.5 mm ball inlet electrode. Translucent stresses that meet the SPLN standard 49-1: 1982, that is ≥ 30 kV at intervals of 2.5 mm were obtained by adding 20 ml of phenol to the volume of used 400 ml transformer oil

scholarly journals Method of calculating the electric strength of oil channels of the main insulation of power transformers

Vestnik IGEU ◽  
2020 ◽  
pp. 48-55
Author(s):  
O.S. Melnikova ◽  
V.S. Kuznetsov
Keyword(s):  
Breakdown Voltage ◽  
High Voltage ◽  
Breakdown Strength ◽  
Dielectric Strength ◽  
Transformer Oil ◽  
Electric Strength ◽  
Power Transformers ◽  
Statistical Characteristics ◽  
Voltage Distribution ◽  
Design Features

The most damage-sensitive unit of power transformers is the main insulation of the oil barrier type. The breakdown of such insulation occurs as a result of the breakdown of the oil channel near the high voltage winding. In accordance with traditional methods of calculating the dielectric strength of insulation, the value of the breakdown strength is determined by empirical formulas depending on the selected width of the oil channel. The existing methods do not consider the influence of the oil channel volume, of the electric strength the statistical characteristics of the oil, the design features of the insulation of power transformers, and do not contain recommendations for creating design models. Thus, to improve the calculation accuracy, it is relevant to develop the evaluation method of dielectric strength of the main insulation of power transformers taking into account the volume and parameters of the breakdown voltage distribution of transformer oil, design features. The research results of the breakdown tension in oil channels with different volumes of transformer oil were used. To improve the accuracy of the calculation and taking into account the design features, the model of the main insulation of power transformers was made in the ANSYS program. Boundary data and assumption of linear stress distribution of transformer coils were considered. A method for calculating the dielectric strength of oil channels of the main insulation of power transformers, considering the volume and parameters of the breakdown voltage distribution of transformer oil was proposed. Unlike the existing methods, when calculating the minimum breakdown strength in the model of the main insulation, the design features of power transformers are taken into account and assumptions are justified to improve the accuracy of the calculation. In accordance with the methodology, the parameters of the dielectric strength of the transformer oil in the oil channel of the high voltage winding of the transformer were calculated. It was concluded that with increase of relative value of breakdown tension, dielectric strength of oil channel is decreasing, and it corresponds to physical sense of breakdown. The method for calculating the dielectric strength of transformer oil can be used when choosing the main insulation of power transformers in design.

The impulse breakdown voltage and time-lag characteristics of long gaps in air II. The negative discharge

1964 ◽  
Vol 256 (1069) ◽  
pp. 213-234 ◽  
Keyword(s):  
Wave Front ◽  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Time Lag ◽  
Time Lags ◽  
Impulse Wave ◽  
Time Resolved ◽  
Wide Range ◽  
Negative Impulse ◽  
Long Time

Oscillographic measurement and time-resolved photographic recording have been used to examine the breakdown of rod/rod, rod/sphere and rod/plane gaps with long-duration negative impulse potentials of up to 1 MV crest. As in the positive discharge, the breakdown process is found often to cease for considerable periods on the impulse wave tail. Breakdown then occurs after a long time lag for gaps composed of rod cathodes and rod or small sphere anodes. Where the anode is large, no long time lags are observed. Measurement of the variation of breakdown strength with time during the impulse duration has been made by the superimposition of a second impulse upon the first, following a controllable delay. The results show a minimum probability of breakdown initiation after 15 μs of the applied impulse, and a subsequent slow recovery. It is suggested that this confirms the effect of the initial corona phase in causing space charge fouling of the gap. The breakdown voltage of rod/rod gaps is shown to decrease by up to 30 % when the impulse wave front is reduced from 0.50 to 0.06 μs. The breakdown strength with negative impulses is thus less than with positive impulses for wave fronts faster than 0.20 μs. For the wave form 0.50/2000 μs, the breakdown voltage is found to depend more critically upon the dimensions of the earthed electrode than is the case with positive impulses. The breakdown voltage for a rod/25 cm sphere gap is 73 % greater than for a rod/rod gap, yet also 15 % greater than for a rod/plane gap. For gap lengths between 25 and 65 cm, the breakdown voltage of the rod/plane gap is found to increase with decreasing wave front duration. The variation of the negative impulse corona with rate of potential rise and with crest voltage is examined photographically. Many of the observed variations of breakdown voltage and time-lag characteristics can be accounted for in terms of the impulse corona phase. The time-resolved photography of the negative discharge over a wide range of conditions suggests that in the range of gap lengths investigated the formation of the positive leader rather than the negative leader is the necessary forerunner of sparkover.

scholarly journals The Modification Mechanism of Nano-Liquids on Streamer Morphology and Breakdown Strength under Microsecond Pulse

2020 ◽  
Vol 10 (20) ◽  
pp. 7376
Author(s):  
Diangeng Li ◽  
Zicheng Zhang ◽  
Shifei Liu ◽  
Song Li
Keyword(s):  
Breakdown Voltage ◽  
Volume Fraction ◽  
Breakdown Strength ◽  
Transformer Oil ◽  
Nano Particles ◽  
Trapped Electrons ◽  
Scientific Consensus ◽  
Breakdown Process ◽  
Microsecond Pulse

In liquid mediums, whether the breakdown strength can be greatly improved after introducing the nano-particles has been widely investigated, however, there has been no scientific consensus on the modification mechanism of this anomalous phenomenon. In this paper, we first experimentally measured the streamer morphology and breakdown strength in pure transformer oil, TiO2 nano-liquids and Al2O3 nano-liquids under microsecond pulse. The results demonstrated that there are significant differences in streamer morphology between pure transformer oil and nano-liquids, as the streamers in pure transformer oil exhibit thick bush-like qualities, while in nano-liquids they exhibit tree-like qualities. Moreover, the breakdown voltage results show that the breakdown strength of transformer oil is improved after nano-modification, and the TiO2 nano-liquids and Al2O3 nano-liquids have nearly the same optimal volume fraction. The results of the analysis indicate that the modification mechanism of nano-particles is significantly linked to the trapped electrons process. Specifically, the addition of nano-particles can affect the electrons’ density and thus affect the breakdown process and streamer morphology.

scholarly journals Study of the effect of cellulose fibers on the electrical strength of transformer oil

Vestnik IGEU ◽  
2020 ◽  
pp. 23-33
Author(s):  
O.S. Melnikova ◽  
M.V. Prusakov ◽  
A.A. Zholobov
Keyword(s):  
Electric Field ◽  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Dielectric Strength ◽  
Cellulose Fibers ◽  
Electrode System ◽  
Transformer Oil ◽  
Electrical Strength ◽  
Abrupt Decrease ◽  
Transformer Insulation

The electrical strength of transformer oil is the first parameter in transformer insulation tests. Such tests are carried out in a standard discharger according to the values of breakdown voltage. An abrupt decrease in electrical strength occurs when oil is contaminated with mechanical impurities. The greatest influence on the electric field is exerted by highly conductive cellulose fibers. The field between the electrodes may be severely distorted bya «bridge» of such fibers. At the same time, the influence of such particles is not taken into account in the tests. The problem is to experimentally determine the effect of such impurities on the breakdown strength. Thereby, this research poses and solves the problem of determining the dielectric strength of transformer oil in a standard discharger in the presence of cellulose fibers.To simulate electric field strengths, the ANSYS software package has been used. The basis of the 3D model was a standard measuring cell for determining breakdown voltage, which takes into account the boundary conditions in the form of a cube in which the electrode system is located, and the values of the electric field strength in the center of the electrode system.The electric field tension between the electrodes has been calculated, taking into account the influence of increased conductivity of cellulose fibers. It has been found that the electrical strength of oil gaps of moistened fibers with a length of more than 200 μm is significantly reduced, which is not taken into account when testing transformer oil for breakdown in a standard cell. This leads to inaccuracy in determining the electric strength of transformer oil in existing equipment.The results of the study can be used by operational services to improve the assessment of the quality of transformer oil used in power transformers as insulation. The results also can be used to study the mechanisms of electrophysical processes occurring in liquid dielectrics in the presence of fibers.

Comparative Study of Size, Total Protein, Fibrinogen and 5-HT Content of Human and Canine Platelet Density Subpopulations

1986 ◽  
Vol 56 (03) ◽  
pp. 288-292 ◽  
Author(s):  
Diego Mezzano ◽  
Eduardo Aranda ◽  
Arnaldo Foradori
Keyword(s):  
Comparative Study ◽  
Protein Content ◽  
Cell Density ◽  
Total Protein ◽  
Unit Volume ◽  
Low Density ◽  
Dense Bodies ◽  
Artifactual Changes ◽  
Platelet Release ◽  
The Difference

SummaryThe size, total protein, fibrinogen and 5-HT content were evaluated in density subpopulations of human and canine platelets fractionated in linear arabinogalactan gradients. The methodology was assessed to ascertain that platelet separation was by density and to discard artifactual changes and platelet release during the procedure. EDTA or PGEi increased the size of human PRP-platelets, but not of dog platelets. In humans, high density (HD) platelets were 1.26 times larger and contained 1.88 times more fibrinogen, 2.23 times more 5-HT and 1.37 times more protein than low density (LD) platelets; in dogs, these density cohorts did not differ in protein content, but LD platelets were 1.29 times larger and had 1.33 times more fibrinogen and 5-HT than HD platelets. These findings suggest that cell density is mostly dependent on the protein content per unit volume of platelets (and not on dense bodies). The differences in fibrinogen and 5-HT content between HD and LD cohorts in humans and dogs may be related to platelet age. The difference in volume between HD and LD platelets in dogs is of uncertain interpretation.

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