Pub Date : 2011-06-26DOI: 10.1109/ICDL.2011.6015426
N. Rudranna, J. S. Rajan
Failure of transformers and reactors due to sulphur in transformer oil is reported in literature. The sulphur in oil by chemical reaction with copper produces copper sulphide which alters the electric field. One of the mitigation techniques followed by manufacturers is replacement of bare copper conductors with enameled copper conductors. In this study, an attempt is made to understand field distribution in transformer insulation due to enamel on the conductor. Finite Element Method (FEM) has been used to understand the electric field distribution in paper and oil with enamel on copper conductor.
{"title":"Effect of enamel covering of copper conductors in paper oil insulation of transformers","authors":"N. Rudranna, J. S. Rajan","doi":"10.1109/ICDL.2011.6015426","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015426","url":null,"abstract":"Failure of transformers and reactors due to sulphur in transformer oil is reported in literature. The sulphur in oil by chemical reaction with copper produces copper sulphide which alters the electric field. One of the mitigation techniques followed by manufacturers is replacement of bare copper conductors with enameled copper conductors. In this study, an attempt is made to understand field distribution in transformer insulation due to enamel on the conductor. Finite Element Method (FEM) has been used to understand the electric field distribution in paper and oil with enamel on copper conductor.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129966842","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015479
M. Hogg, I. Timoshkin, M. Given, M. Wilson, S. Macgregor, R. Fouracre, J. Lehr
The complexity of the impulse breakdown of liquid water is reflected by the dependency of pre-breakdown processes on the polarity, rise-time and wave-shape of the applied impulses as well as on physical properties, such as electrical conductivity of water itself. Further understanding of the mechanisms of formation and propagation of impulse discharges in water and water solutions is therefore required to enable the development of pulsed power and plasma technologies. The paper presents a study of the dielectric behaviour of water stressed with high voltage impulses in a point-plane electrode topology. Water with different conductivities including distilled water, tap water and a water based ionic solution was investigated. The volt-time breakdown characteristic of water is discussed and the pre-breakdown time and nominal breakdown velocity have been obtained for both positive and negative polarity impulses. Potential breakdown mechanisms which can explain the observed polarity effects in the transient pre-breakdown processes in liquid water stressed with high voltage impulses are discussed.
{"title":"Liquid water stressed with HV impulses: Effect of polarity on transient pre-breakdown processes","authors":"M. Hogg, I. Timoshkin, M. Given, M. Wilson, S. Macgregor, R. Fouracre, J. Lehr","doi":"10.1109/ICDL.2011.6015479","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015479","url":null,"abstract":"The complexity of the impulse breakdown of liquid water is reflected by the dependency of pre-breakdown processes on the polarity, rise-time and wave-shape of the applied impulses as well as on physical properties, such as electrical conductivity of water itself. Further understanding of the mechanisms of formation and propagation of impulse discharges in water and water solutions is therefore required to enable the development of pulsed power and plasma technologies. The paper presents a study of the dielectric behaviour of water stressed with high voltage impulses in a point-plane electrode topology. Water with different conductivities including distilled water, tap water and a water based ionic solution was investigated. The volt-time breakdown characteristic of water is discussed and the pre-breakdown time and nominal breakdown velocity have been obtained for both positive and negative polarity impulses. Potential breakdown mechanisms which can explain the observed polarity effects in the transient pre-breakdown processes in liquid water stressed with high voltage impulses are discussed.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128228896","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015467
P. A. Vázquez, A. Castellanos
The 3D Electrohydrodynamic convection between parallel plates immersed in a dielectric liquid is studied numerically in a cylindrical cell. The distribution of charge is computed with Particl-In-Cell, the electric field with finite elements and the velocity field with an imposed roll. Critical values of the stability parameter are obtained for different mobilities and are compared with the value from the linear stability analysis.
{"title":"Stability analysis of the 3D electroconvective charged flow between parallel plates using the Particle-In-Cell method","authors":"P. A. Vázquez, A. Castellanos","doi":"10.1109/ICDL.2011.6015467","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015467","url":null,"abstract":"The 3D Electrohydrodynamic convection between parallel plates immersed in a dielectric liquid is studied numerically in a cylindrical cell. The distribution of charge is computed with Particl-In-Cell, the electric field with finite elements and the velocity field with an imposed roll. Critical values of the stability parameter are obtained for different mobilities and are compared with the value from the linear stability analysis.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133544968","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015471
J. Raisin, P. Atten, J. Reboud
The basic process of coalescence of droplets in a flowing water-in-oil emulsion under the action of an electric field is considered. The coalescence probability depends on the ratio of time of close proximity of droplets and time of decrease of spacing down to drops contact. For two free drops aligned with the field, the dynamical problem consists in the deformation of the drops, their motion and the thinning of the oil film between the drops. For very small droplets, assuming a negligible interface deformation, a very small initial spacing and a high value of viscosity ratio leads to an order of magnitude estimate of the time required for the drops to achieve contact. Numerical simulations confirm that this time is roughly inversely proportional to the maximum initial electrostatic pressure pe0 at the facing interfaces and point up an influence of the electric Bond number defined as the ratio of electric and capillary forces.
{"title":"Field induced coalescence of two free water drops in a viscous dielectric fluid","authors":"J. Raisin, P. Atten, J. Reboud","doi":"10.1109/ICDL.2011.6015471","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015471","url":null,"abstract":"The basic process of coalescence of droplets in a flowing water-in-oil emulsion under the action of an electric field is considered. The coalescence probability depends on the ratio of time of close proximity of droplets and time of decrease of spacing down to drops contact. For two free drops aligned with the field, the dynamical problem consists in the deformation of the drops, their motion and the thinning of the oil film between the drops. For very small droplets, assuming a negligible interface deformation, a very small initial spacing and a high value of viscosity ratio leads to an order of magnitude estimate of the time required for the drops to achieve contact. Numerical simulations confirm that this time is roughly inversely proportional to the maximum initial electrostatic pressure pe0 at the facing interfaces and point up an influence of the electric Bond number defined as the ratio of electric and capillary forces.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132662697","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015454
D. Linhjell, S. Ingebrigtsen, L. Lundgaard, M. Unge
This is a study of the effect of the additives dimethylaniline (DMA) and trichloroethylene (TCE) on the pre-breakdown phenomena known as streamers, in a simple base liquid, cyclohexane. This has been done under a step-like impulse voltage in a long point-plane gap. The objective was mainly to find out which aspects of the chemistry of mineral transformer oils cause their good streamer-related dielectric properties, in particular the high voltage for the transition to a very fast mode of positive streamers, as pure cyclohexane does not have these good properties. It is found that DMA added indeed causes positive streamers to become very similar to positive streamers in mineral oil and has no effect on negative streamers. TCE causes the negative streamers to become more mineral-oil-like, and has only a little effect on positive streamers.
{"title":"Streamers in long point-plane gaps in cyclohexane with and without additives under step voltage","authors":"D. Linhjell, S. Ingebrigtsen, L. Lundgaard, M. Unge","doi":"10.1109/ICDL.2011.6015454","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015454","url":null,"abstract":"This is a study of the effect of the additives dimethylaniline (DMA) and trichloroethylene (TCE) on the pre-breakdown phenomena known as streamers, in a simple base liquid, cyclohexane. This has been done under a step-like impulse voltage in a long point-plane gap. The objective was mainly to find out which aspects of the chemistry of mineral transformer oils cause their good streamer-related dielectric properties, in particular the high voltage for the transition to a very fast mode of positive streamers, as pure cyclohexane does not have these good properties. It is found that DMA added indeed causes positive streamers to become very similar to positive streamers in mineral oil and has no effect on negative streamers. TCE causes the negative streamers to become more mineral-oil-like, and has only a little effect on positive streamers.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130567491","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015480
M. Wilson, I. Timoshkin, M. Given, S. Macgregor, M. Sinclair, K. Thomas, J. Lehr
Experimental data on the propagation of streamers in mineral oil is important for the design of high-voltage systems in the power and pulsed-power industries. In the present study, pre-breakdown delay times were measured for plane-parallel electrodes, and for two types of non-uniform electrode arrangement. For each geometry, the breakdown characteristics were determined for impulses of rise-time 100 ns, and also rise-time 1 µs. The maximum applied voltage magnitude was 400 kV, giving a maximum dV/dt of 4 kV/ns. For the non-uniform geometries with inter-electrode gap length of 8.5 mm, the time to breakdown was 2.5–3 times longer for impulses of rise-time 1 µs than for 100 ns rise-time. The time-to-breakdown data suggest that streamer propagation velocity increases with higher values of dV/dt. For example, the estimated propagation velocity for pin-plane geometry with a 1 µs rise-time is 10–12 km/s. At 100 ns rise-time for the same electrode geometry, the average propagation velocity exceeds 40 km/s. The results presented are intended to provide reference data for designers of oil-immersed high-voltage systems in both the power and pulsed-power industries.
{"title":"Effect of electrode geometry and rate of voltage rise on streamer propagation in mineral oil","authors":"M. Wilson, I. Timoshkin, M. Given, S. Macgregor, M. Sinclair, K. Thomas, J. Lehr","doi":"10.1109/ICDL.2011.6015480","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015480","url":null,"abstract":"Experimental data on the propagation of streamers in mineral oil is important for the design of high-voltage systems in the power and pulsed-power industries. In the present study, pre-breakdown delay times were measured for plane-parallel electrodes, and for two types of non-uniform electrode arrangement. For each geometry, the breakdown characteristics were determined for impulses of rise-time 100 ns, and also rise-time 1 µs. The maximum applied voltage magnitude was 400 kV, giving a maximum dV/dt of 4 kV/ns. For the non-uniform geometries with inter-electrode gap length of 8.5 mm, the time to breakdown was 2.5–3 times longer for impulses of rise-time 1 µs than for 100 ns rise-time. The time-to-breakdown data suggest that streamer propagation velocity increases with higher values of dV/dt. For example, the estimated propagation velocity for pin-plane geometry with a 1 µs rise-time is 10–12 km/s. At 100 ns rise-time for the same electrode geometry, the average propagation velocity exceeds 40 km/s. The results presented are intended to provide reference data for designers of oil-immersed high-voltage systems in both the power and pulsed-power industries.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129593343","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015493
W. Schmidt, G. Bakale, A. Khrapak, K. Yoshino
Ionic and electronic charge carriers are usually injected into dielectric liquids either by ionization by high energy radiation or by photoelectric effect at an electrode. Here, we summarize and discuss data on the drift velocity as a function of applied electric field obtained with these methods. While the drift of ions can be described by Stokes' law of laminar motion up to the highest field strengths measured, the drift of electrons at higher electric field strengths is characterized by an increase of their energy above the thermal energy of the liquid, which enables them to initiate electronic reactions. The importance for the description of electric breakdown processes will be discussed.
{"title":"Drift velocity of ions and electrons in non-polar dielectric liquids at high electric field strengths","authors":"W. Schmidt, G. Bakale, A. Khrapak, K. Yoshino","doi":"10.1109/ICDL.2011.6015493","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015493","url":null,"abstract":"Ionic and electronic charge carriers are usually injected into dielectric liquids either by ionization by high energy radiation or by photoelectric effect at an electrode. Here, we summarize and discuss data on the drift velocity as a function of applied electric field obtained with these methods. While the drift of ions can be described by Stokes' law of laminar motion up to the highest field strengths measured, the drift of electrons at higher electric field strengths is characterized by an increase of their energy above the thermal energy of the liquid, which enables them to initiate electronic reactions. The importance for the description of electric breakdown processes will be discussed.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129777043","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015476
P. Lukeš, M. Člupek, V. Babický, P. Šunka
Electrical breakdown of water using porous ceramic-coated rod electrodes were investigated for two types of ceramics, oxide (corundum) and silicates (almandine). Properties of the ceramic layer and its interaction with the electrolyte, i.e., surface chemistry at the electrolyte/ceramic surface interface, were found as important factors in generating electrical discharges in water. The buildup of surface charge, which was determined by the polarity of the applied voltage, pH and chemical composition of aqueous solution, led to the formation of an electrical double layer at the ceramic surface. Under an externally applied electric field, this double layer becomes polarized, which affected the electric field distribution on the ceramic electrode and conditions needed for initiation of the discharge in water.
{"title":"Electrical breakdown of water using porous ceramic-coated electrode","authors":"P. Lukeš, M. Člupek, V. Babický, P. Šunka","doi":"10.1109/ICDL.2011.6015476","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015476","url":null,"abstract":"Electrical breakdown of water using porous ceramic-coated rod electrodes were investigated for two types of ceramics, oxide (corundum) and silicates (almandine). Properties of the ceramic layer and its interaction with the electrolyte, i.e., surface chemistry at the electrolyte/ceramic surface interface, were found as important factors in generating electrical discharges in water. The buildup of surface charge, which was determined by the polarity of the applied voltage, pH and chemical composition of aqueous solution, led to the formation of an electrical double layer at the ceramic surface. Under an externally applied electric field, this double layer becomes polarized, which affected the electric field distribution on the ceramic electrode and conditions needed for initiation of the discharge in water.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129577433","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015457
M. Jovalekic, D. Vuković, S. Tenbohlen
Dissolved gas in oil analysis (DGA) has been used for many years successfully for diagnosis and condition monitoring of mineral oil filled transformers. In future the diagnostic methods have to be transferred to new fluids. This contribution presents results of the gassing behavior of different insulating liquids from experiments, which represent electrical and thermal faults. Also the suitability of existing mineral oil interpretation methods for DGA is considered. The main investigated fluid is Envirotemp® FR3™. Where possible the amount and relation of the gases are compared to mineral oil and other synthetic esters gassing behaviour.
{"title":"Dissolved gas analysis of alternative dielectric fluids under thermal and electrical stress","authors":"M. Jovalekic, D. Vuković, S. Tenbohlen","doi":"10.1109/ICDL.2011.6015457","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015457","url":null,"abstract":"Dissolved gas in oil analysis (DGA) has been used for many years successfully for diagnosis and condition monitoring of mineral oil filled transformers. In future the diagnostic methods have to be transferred to new fluids. This contribution presents results of the gassing behavior of different insulating liquids from experiments, which represent electrical and thermal faults. Also the suitability of existing mineral oil interpretation methods for DGA is considered. The main investigated fluid is Envirotemp® FR3™. Where possible the amount and relation of the gases are compared to mineral oil and other synthetic esters gassing behaviour.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128720970","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 : 2011-06-26DOI: 10.1109/ICDL.2011.6015478
J. Viertel, K. Ohlsson, S. Singha
This work reports on an experimental study of the aging behavior of thin films of different classes of natural ester dielectric liquids. Thin film samples of three different natural ester liquids were prepared for the investigations and the aging experiments were performed in a medium of dry air at different temperatures (23°C and 65°C) and durations (up to around 100 days). The degradation of the samples was then evaluated in terms of changes in the dynamic viscosity of the liquid. Further analyses were also performed on the aged liquids through visual inspection, Infrared (IR) spectroscopy analysis and Oxidative Induction Time (OIT) measurements. Results show that the aging behaviors of natural ester dielectric liquids may greatly vary depending on the base chemistry of the liquid. Based on these results, it is suggested that natural ester dielectric liquids be classified into different categories considering their oleic acid content.
{"title":"Thermal aging and degradation of thin films of natural ester dielectric liquids","authors":"J. Viertel, K. Ohlsson, S. Singha","doi":"10.1109/ICDL.2011.6015478","DOIUrl":"https://doi.org/10.1109/ICDL.2011.6015478","url":null,"abstract":"This work reports on an experimental study of the aging behavior of thin films of different classes of natural ester dielectric liquids. Thin film samples of three different natural ester liquids were prepared for the investigations and the aging experiments were performed in a medium of dry air at different temperatures (23°C and 65°C) and durations (up to around 100 days). The degradation of the samples was then evaluated in terms of changes in the dynamic viscosity of the liquid. Further analyses were also performed on the aged liquids through visual inspection, Infrared (IR) spectroscopy analysis and Oxidative Induction Time (OIT) measurements. Results show that the aging behaviors of natural ester dielectric liquids may greatly vary depending on the base chemistry of the liquid. Based on these results, it is suggested that natural ester dielectric liquids be classified into different categories considering their oleic acid content.","PeriodicalId":364451,"journal":{"name":"2011 IEEE International Conference on Dielectric Liquids","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115838860","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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