Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893112
I. Hosier, J. Gu, W. Chotchuangchutchavel, A. Vaughan
The effect of viscosity on AC breakdown strength was studied using aged sunflower oil. After ageing, the oil was darkened and the viscosity and water content increased. Whilst the electrical conductivity increased with ageing as anticipated, the AC breakdown strength showed an unexpected increase. In addition the effect of water on breakdown strength was probed using carefully treated olive oil. Whilst extended periods of drying did not change the electrical properties, adding water increased the electrical conductivity and reduced the breakdown strength. This indicates that increased viscosity is the cause of the observed unexpected increases in AC breakdown strength.
{"title":"Effect of viscosity and water content on the breakdown strength of vegetable oils","authors":"I. Hosier, J. Gu, W. Chotchuangchutchavel, A. Vaughan","doi":"10.1109/ICDL.2014.6893112","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893112","url":null,"abstract":"The effect of viscosity on AC breakdown strength was studied using aged sunflower oil. After ageing, the oil was darkened and the viscosity and water content increased. Whilst the electrical conductivity increased with ageing as anticipated, the AC breakdown strength showed an unexpected increase. In addition the effect of water on breakdown strength was probed using carefully treated olive oil. Whilst extended periods of drying did not change the electrical properties, adding water increased the electrical conductivity and reduced the breakdown strength. This indicates that increased viscosity is the cause of the observed unexpected increases in AC breakdown strength.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"50 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88183663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893137
A. Akshatha, Kumar A. Ravi, J. S. Rajan, K. Murthy, G. Viswanath, H. Ramachandra
This study was taken up to understand the variations in concentrations of metal passivators like Irgamet 39 and BTA which are added to mitigate the effects of corrosive sulphur in mineral oil. The study has shown that both BTA and Irgamet 39 are effective in arresting the formation of copper sulphide on conductors. The effect of thermal ageing of oil in presence of reactive species like MBT and DBDS on the concentrations of passivators has been studied and discussed in this paper.
{"title":"Assessment of passivated mineral oil in mitigating the formation of copper sulphide in transformers","authors":"A. Akshatha, Kumar A. Ravi, J. S. Rajan, K. Murthy, G. Viswanath, H. Ramachandra","doi":"10.1109/ICDL.2014.6893137","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893137","url":null,"abstract":"This study was taken up to understand the variations in concentrations of metal passivators like Irgamet 39 and BTA which are added to mitigate the effects of corrosive sulphur in mineral oil. The study has shown that both BTA and Irgamet 39 are effective in arresting the formation of copper sulphide on conductors. The effect of thermal ageing of oil in presence of reactive species like MBT and DBDS on the concentrations of passivators has been studied and discussed in this paper.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"17 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87410499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893094
P. Traoré, Jian Wu, C. Louste, P. Vázquez, A. Pérez
In this paper, the interaction between a plane Poiseuille channel flow and an electroconvective movement induced by the electric field is investigated. A flow is generated by an inlet parabolic profile in a rectangular duct. Space charges are injected in the flow through a metallic electrode placed on one of the channel walls and brought to a given potential. Transient numerical simulations have been carried out to investigate the structure of the flow. The entire set of the coupled Navier-Stokes and EHD equations are solved using an efficient finite volume technique. The behavior of the flow subjected to an applied voltage between the two electrodes is analyzed and time evolution of the charge density distributions is presented. The interaction between the convective movement induced by space charge injection and electric field and the mainstream flow, emphasizes the appearance of periodic transverse traveling waves convected in the channel. For a given Reynolds number it exists a threshold value of the instability parameters T over which the transverse traveling waves appear or not.
{"title":"Stability of a plane Poiseuille channel flow of a dielectric liquid subjected to unipolar injection","authors":"P. Traoré, Jian Wu, C. Louste, P. Vázquez, A. Pérez","doi":"10.1109/ICDL.2014.6893094","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893094","url":null,"abstract":"In this paper, the interaction between a plane Poiseuille channel flow and an electroconvective movement induced by the electric field is investigated. A flow is generated by an inlet parabolic profile in a rectangular duct. Space charges are injected in the flow through a metallic electrode placed on one of the channel walls and brought to a given potential. Transient numerical simulations have been carried out to investigate the structure of the flow. The entire set of the coupled Navier-Stokes and EHD equations are solved using an efficient finite volume technique. The behavior of the flow subjected to an applied voltage between the two electrodes is analyzed and time evolution of the charge density distributions is presented. The interaction between the convective movement induced by space charge injection and electric field and the mainstream flow, emphasizes the appearance of periodic transverse traveling waves convected in the channel. For a given Reynolds number it exists a threshold value of the instability parameters T over which the transverse traveling waves appear or not.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"58 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91136560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893071
N. V. Dung, D. Linhjell, L. Lundgaard, H. Hoidalen, M. Unge
Streamer propagation guided within PTFE tubes were investigated in an 8 cm point-plane gap in white oil. Both positive and negative polarities were studied with a near step voltage of 50-400 kV. Streamers in a free volume were compared with those in tubes. Within tubes, branching of streamers is suppressed, and interaction between streamers and tube wall may occur. For positive streamers, the guiding tube slightly accelerates streamers and reduces acceleration voltage. However, for negative streamers the tube significantly increases the velocity and drastically decreases the acceleration voltage. Possibly, streamer propagation is governed by the streamers tip-field. When the interaction between streamers and the tube wall appears, the electric field at the streamer tip is increased. This leads to an increase in streamer velocity. The mechanism of streamer propagation is discussed.
{"title":"Effects of spatial restriction on streamers in white oil","authors":"N. V. Dung, D. Linhjell, L. Lundgaard, H. Hoidalen, M. Unge","doi":"10.1109/ICDL.2014.6893071","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893071","url":null,"abstract":"Streamer propagation guided within PTFE tubes were investigated in an 8 cm point-plane gap in white oil. Both positive and negative polarities were studied with a near step voltage of 50-400 kV. Streamers in a free volume were compared with those in tubes. Within tubes, branching of streamers is suppressed, and interaction between streamers and tube wall may occur. For positive streamers, the guiding tube slightly accelerates streamers and reduces acceleration voltage. However, for negative streamers the tube significantly increases the velocity and drastically decreases the acceleration voltage. Possibly, streamer propagation is governed by the streamers tip-field. When the interaction between streamers and the tube wall appears, the electric field at the streamer tip is increased. This leads to an increase in streamer velocity. The mechanism of streamer propagation is discussed.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"18 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89663225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893158
W. Lu, X. Wang, Q. Liu
In insulating liquids, a breakdown event is the consequence of streamer initiation and propagation. A number of parameters such as stopping length, propagation velocity, and current and light pulses can be used to characterize the streamer phenomenon. In addition, it is recognized that the geometric patterns of streamers in insulating liquids are with a fractal nature and the shape complexity of streamer patterns can be analyzed by using fractal index, i.e. fractal dimension. This paper described the fractal features of streamer patterns in a synthetic ester insulating liquid under lightning impulse voltages. The fractal dimensions of streamer patterns at different propagation times and voltage levels were calculated by using box-counting method. Relationships between fractal index and other parameters such as stopping length and streamer area were finally presented. Results indicate that fractal dimension with propagation time and applied voltage follows the similar trend to streamer length and area. All of them generally increase with the increase of propagation time and applied voltage level.
{"title":"Fractal index of streamer patterns in insulating liquids under lightning impulse voltages","authors":"W. Lu, X. Wang, Q. Liu","doi":"10.1109/ICDL.2014.6893158","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893158","url":null,"abstract":"In insulating liquids, a breakdown event is the consequence of streamer initiation and propagation. A number of parameters such as stopping length, propagation velocity, and current and light pulses can be used to characterize the streamer phenomenon. In addition, it is recognized that the geometric patterns of streamers in insulating liquids are with a fractal nature and the shape complexity of streamer patterns can be analyzed by using fractal index, i.e. fractal dimension. This paper described the fractal features of streamer patterns in a synthetic ester insulating liquid under lightning impulse voltages. The fractal dimensions of streamer patterns at different propagation times and voltage levels were calculated by using box-counting method. Relationships between fractal index and other parameters such as stopping length and streamer area were finally presented. Results indicate that fractal dimension with propagation time and applied voltage follows the similar trend to streamer length and area. All of them generally increase with the increase of propagation time and applied voltage level.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":" 11","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91415867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893144
Yuan Zhou, M. Hao, George Chen, P. Jarman, G. Wilson
Polarization and depolarization current measurement is a non-destructive testing method to study the dielectric properties of insulating materials. Two kinds of mineral oils with different aging time have been measured and compared. When the charge carriers drift to the electrodes, they may be blocked and accumulated in the vicinity of the electrode to form the charge layers. When the oil is discharged, the charge carriers in these charge layers will start to move backwards to the bulk and result in a depolarization current. The depolarization process can be affected by both diffusion and electric drift. In this paper, the diffusion theory has been used to study the depolarization in mineral oil and the experimental results have been fitted using exponential equations. It seems the depolarization current is mainly contributed by the diffusion of the charge carriers in the mineral oil. The assumption that there are two kinds of charge carriers in the mineral oil that made in frequency domain measurement has been verified in this paper.
{"title":"Study of the depolarization current in mineral oils","authors":"Yuan Zhou, M. Hao, George Chen, P. Jarman, G. Wilson","doi":"10.1109/ICDL.2014.6893144","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893144","url":null,"abstract":"Polarization and depolarization current measurement is a non-destructive testing method to study the dielectric properties of insulating materials. Two kinds of mineral oils with different aging time have been measured and compared. When the charge carriers drift to the electrodes, they may be blocked and accumulated in the vicinity of the electrode to form the charge layers. When the oil is discharged, the charge carriers in these charge layers will start to move backwards to the bulk and result in a depolarization current. The depolarization process can be affected by both diffusion and electric drift. In this paper, the diffusion theory has been used to study the depolarization in mineral oil and the experimental results have been fitted using exponential equations. It seems the depolarization current is mainly contributed by the diffusion of the charge carriers in the mineral oil. The assumption that there are two kinds of charge carriers in the mineral oil that made in frequency domain measurement has been verified in this paper.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"157 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79907500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893164
O. Lesaint, A. Denat, F. Mccluskey
The objective of this study is to document the relationship existing between liquid composition and streamer propagation in large gaps. Measurements are carried out in a series of hydrocarbon liquids of various chemical natures (aliphatic, aromatic, polyaromatic), both in short point-plane gap (6 mm distance, 1 μm tip radius), and in larger gaps up to 20 cm. These measurements are based on fast imaging techniques (2D and streak photographs), coupled to transient current and light recording. A correlation is established between the threshold propagation voltage of filamentary streamers, the tendency to form branches, and the behaviour at very high voltage.
{"title":"Positive streamers in short and large gaps in hydrocarbons of various chemical natures","authors":"O. Lesaint, A. Denat, F. Mccluskey","doi":"10.1109/ICDL.2014.6893164","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893164","url":null,"abstract":"The objective of this study is to document the relationship existing between liquid composition and streamer propagation in large gaps. Measurements are carried out in a series of hydrocarbon liquids of various chemical natures (aliphatic, aromatic, polyaromatic), both in short point-plane gap (6 mm distance, 1 μm tip radius), and in larger gaps up to 20 cm. These measurements are based on fast imaging techniques (2D and streak photographs), coupled to transient current and light recording. A correlation is established between the threshold propagation voltage of filamentary streamers, the tendency to form branches, and the behaviour at very high voltage.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"17 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83659627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893149
D. Karpov, A. L. Kupershtokh
The method of molecular dynamics (MD) was applied to study the processes in liquid and dense gas under the action of an extremely high electric field. Two following model for a dielectric was used. A substance consisted of the molecules with a constant electrical dipole moment. The parallel code was specially developed using the CUDA technology in order to produce the computations of large ensembles of the molecules with the MD method using the high-performance graphic cards. The correlation function of the orientation of the dipole molecules was calculated for various densities of the substance. The density dependence was studied of the radius of the region in which the ion influences on the molecules with the constant dipole moment. The density dependency of the electric potential well depth near the ion placed in a polar dielectric was obtained. The formation of vapour channels in a liquid dielectric under the action of extremely high electric field (anisotropic spinodal decomposition) was also simulated. It was shown that channels are formed approximately along the electric force lines and the process looks like the formation of cracks in solid body due to mechanical stresses. The results obtained are important for understanding the microprocesses preceding a streamer formation during the process of discharge development in dielectric liquids.
{"title":"Study of microstructure of dielectric liquid in high electric field","authors":"D. Karpov, A. L. Kupershtokh","doi":"10.1109/ICDL.2014.6893149","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893149","url":null,"abstract":"The method of molecular dynamics (MD) was applied to study the processes in liquid and dense gas under the action of an extremely high electric field. Two following model for a dielectric was used. A substance consisted of the molecules with a constant electrical dipole moment. The parallel code was specially developed using the CUDA technology in order to produce the computations of large ensembles of the molecules with the MD method using the high-performance graphic cards. The correlation function of the orientation of the dipole molecules was calculated for various densities of the substance. The density dependence was studied of the radius of the region in which the ion influences on the molecules with the constant dipole moment. The density dependency of the electric potential well depth near the ion placed in a polar dielectric was obtained. The formation of vapour channels in a liquid dielectric under the action of extremely high electric field (anisotropic spinodal decomposition) was also simulated. It was shown that channels are formed approximately along the electric force lines and the process looks like the formation of cracks in solid body due to mechanical stresses. The results obtained are important for understanding the microprocesses preceding a streamer formation during the process of discharge development in dielectric liquids.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"55 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80289054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893136
S. Flora, M.Kanya Kumari, J.Sundara Rajan
This study presents the FEM (Finite Element Method) results of electric stress analysis of copper sulphide contaminated paper insulation of transformers. This analysis is based on conductivity and permittivity changes that occur due to penetration of copper sulphide into paper. The differences in the two models based on conductivity and permittivity and their effect on electric stress distribution are discussed. Results show more variation in the maximum electric stress across the paper layers in the conductivity model than in the permittivity model.
{"title":"Study of modification of electric field distribution in paper-oil insulation of transformer in the presence of copper sulphide","authors":"S. Flora, M.Kanya Kumari, J.Sundara Rajan","doi":"10.1109/ICDL.2014.6893136","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893136","url":null,"abstract":"This study presents the FEM (Finite Element Method) results of electric stress analysis of copper sulphide contaminated paper insulation of transformers. This analysis is based on conductivity and permittivity changes that occur due to penetration of copper sulphide into paper. The differences in the two models based on conductivity and permittivity and their effect on electric stress distribution are discussed. Results show more variation in the maximum electric stress across the paper layers in the conductivity model than in the permittivity model.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"24 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81532927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-08DOI: 10.1109/ICDL.2014.6893099
K. Yoshino, W. Schmidt
Silicone oils are possible replacements for mineral oils in transformers. Many investigations on their electrical and thermo-physical properties have been carried out. Few reports on the measurements of the mobilities of positive and negative ions in these liquids exist in the literature. The present contribution summarizes data published and discusses the modes of charge transport in these liquids.
{"title":"Ion Mobilities in poly-dimethylsiloxane silicone oils","authors":"K. Yoshino, W. Schmidt","doi":"10.1109/ICDL.2014.6893099","DOIUrl":"https://doi.org/10.1109/ICDL.2014.6893099","url":null,"abstract":"Silicone oils are possible replacements for mineral oils in transformers. Many investigations on their electrical and thermo-physical properties have been carried out. Few reports on the measurements of the mobilities of positive and negative ions in these liquids exist in the literature. The present contribution summarizes data published and discusses the modes of charge transport in these liquids.","PeriodicalId":6523,"journal":{"name":"2014 IEEE 18th International Conference on Dielectric Liquids (ICDL)","volume":"11 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2014-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75981369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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