It is noted that the temperature dependence of ILC (injection-limited current) is naturally described by thermally activated escape of the carriers from the Coulombic potential well. It is usually assumed and often observed that the activation energy of this process is a temperature-independent quantity. It is shown that the activation energy is, in general, a function of temperature; the shape of the function is determined by spatial distribution of the source current. The Arrhenius law appears as a consequence of expressing the weak gradient function characterizing the injecting contact by a delta function, which is physically unjustified and must be questioned.<>
{"title":"Temperature dependence of injection-limited currents in dielectrics","authors":"J. Godlewski, B. Strzelecka, J. Kalinowski","doi":"10.1109/ICSD.1989.69183","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69183","url":null,"abstract":"It is noted that the temperature dependence of ILC (injection-limited current) is naturally described by thermally activated escape of the carriers from the Coulombic potential well. It is usually assumed and often observed that the activation energy of this process is a temperature-independent quantity. It is shown that the activation energy is, in general, a function of temperature; the shape of the function is determined by spatial distribution of the source current. The Arrhenius law appears as a consequence of expressing the weak gradient function characterizing the injecting contact by a delta function, which is physically unjustified and must be questioned.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129780077","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}
The insulation performance of PE (polyethylene) under DC voltage was investigated using sheet samples and miniature cables. Pressed sheets of various kinds of PE, which differed in material density and polymerization process, were prepared, and their thermally stimulated current and breakdown strength were measured. To confirm that insulating properties obtained in the experiments using sheet samples can also be obtained in thicker samples, experiments were conducted using miniature cables with 3.5-mm insulation thickness and a conductor cross-sectional area of 60 mm/sup 2/ to evaluate breakdown strength and to measure the thermally stimulated current. Both sets of results showed that HDPE (high-density PE) has excellent insulating properties under DC voltage. The breakdown strength is high and the space charge accumulation is small. These properties of HDPE are considered to be due to its molecular structure, with its short lengths of molecular branches.<>
{"title":"DC characteristics of cable insulating materials","authors":"T. Suzuki, S. Katakai, M. Kanaoka, Y. Sekii","doi":"10.1109/ICSD.1989.69163","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69163","url":null,"abstract":"The insulation performance of PE (polyethylene) under DC voltage was investigated using sheet samples and miniature cables. Pressed sheets of various kinds of PE, which differed in material density and polymerization process, were prepared, and their thermally stimulated current and breakdown strength were measured. To confirm that insulating properties obtained in the experiments using sheet samples can also be obtained in thicker samples, experiments were conducted using miniature cables with 3.5-mm insulation thickness and a conductor cross-sectional area of 60 mm/sup 2/ to evaluate breakdown strength and to measure the thermally stimulated current. Both sets of results showed that HDPE (high-density PE) has excellent insulating properties under DC voltage. The breakdown strength is high and the space charge accumulation is small. These properties of HDPE are considered to be due to its molecular structure, with its short lengths of molecular branches.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122374282","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}
A novel method for the detection of high-field AC conduction loss current in polymeric insulating materials is developed. It uses the unbalanced operation of a current-comparator-type high-field tan- delta -capacitance bridge and the deconvolution technique for signal processing. Examples of the transfer function of this detection system for different amplifier gain levels are shown. Under certain conditions, the high-field AC conduction current of LDPE (low-density polyethylene) film evaluated with this method contains both an in-phase fundamental sine wave component which correlates with tan delta and harmonics caused by the nonlinear electric-field dependence of the conduction current. In epoxy resin, however, only the fundamental sinusoidal wave component of the dissipation current is detected.<>
{"title":"Detection of high field AC conduction loss current in polymeric insulating materials","authors":"T. Tokoro, M. Nagao, M. Kosaki","doi":"10.1109/ICSD.1989.69198","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69198","url":null,"abstract":"A novel method for the detection of high-field AC conduction loss current in polymeric insulating materials is developed. It uses the unbalanced operation of a current-comparator-type high-field tan- delta -capacitance bridge and the deconvolution technique for signal processing. Examples of the transfer function of this detection system for different amplifier gain levels are shown. Under certain conditions, the high-field AC conduction current of LDPE (low-density polyethylene) film evaluated with this method contains both an in-phase fundamental sine wave component which correlates with tan delta and harmonics caused by the nonlinear electric-field dependence of the conduction current. In epoxy resin, however, only the fundamental sinusoidal wave component of the dissipation current is detected.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"154 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132372206","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}
R. Fouracre, H. M. Banford, X. Cao, H. Wang, D. Tedford
A research program has been undertaken in which material is exposed to irradiation up to dose levels of 2 MGy. This represents the exposure anticipated over the lifetime of the material. Samples of epoxy resins and polyimide film were exposed to gamma rays from a Co source. Measurements of thermally stimulated discharge currents (TSDC) were made on all samples both before and after irradiation. The results for the epoxy resins may be explained in terms of the creation of mobile ions and the cross-linking of either unreacted hardener or resin during irradiation. Results for polyimide are consistent with space-charge-limited conduction.<>
{"title":"Radiation effects in polymers","authors":"R. Fouracre, H. M. Banford, X. Cao, H. Wang, D. Tedford","doi":"10.1109/ICSD.1989.69243","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69243","url":null,"abstract":"A research program has been undertaken in which material is exposed to irradiation up to dose levels of 2 MGy. This represents the exposure anticipated over the lifetime of the material. Samples of epoxy resins and polyimide film were exposed to gamma rays from a Co source. Measurements of thermally stimulated discharge currents (TSDC) were made on all samples both before and after irradiation. The results for the epoxy resins may be explained in terms of the creation of mobile ions and the cross-linking of either unreacted hardener or resin during irradiation. Results for polyimide are consistent with space-charge-limited conduction.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125584818","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}
B. Fruth, G. Lipták, L. Ullrich, T. Dunz, L. Niemeyer
The long-term ageing of insulator models until breakdown was investigated with repetitive diagnostic measurements. The physical mechanisms in models with isolated defects were examined, and improved diagnostic tools were developed on the basis of the ageing experiments. Experimental results on the properties of a mica paper, glass fiber, and epoxy resin composite are presented. The authors discuss the effect of temperature on ageing and especially on defect induction by thermomechanical forces.<>
{"title":"Ageing of rotating machines insulation-mechanisms, measurement techniques","authors":"B. Fruth, G. Lipták, L. Ullrich, T. Dunz, L. Niemeyer","doi":"10.1109/ICSD.1989.69266","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69266","url":null,"abstract":"The long-term ageing of insulator models until breakdown was investigated with repetitive diagnostic measurements. The physical mechanisms in models with isolated defects were examined, and improved diagnostic tools were developed on the basis of the ageing experiments. Experimental results on the properties of a mica paper, glass fiber, and epoxy resin composite are presented. The authors discuss the effect of temperature on ageing and especially on defect induction by thermomechanical forces.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115844846","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}
G. Matey, F. Nicoulaz, J. Filippini, Y. Poggi, Ramdane Bouzerara
The authors discuss complementary studies on the effect of temperature on water tree growth, conducted at two different laboratories, using the same LDPE (low-density polyethylene) reference product at 23 degrees C and 65 degrees C, in a point-to-plane geometry. These very similar tests yielded totally contradictory conclusions on the effect of temperature on water tree growth. In one test the water trees propagated more favourably at 23 degrees C than at 65 degrees C. In the other test the water trees grew larger at 65 degrees C than at 23 degrees C. The latter result has been observed exclusively in the case of a wet grounding environment. As this was the only fundamental difference between the tests, the authors hypothesize that the enhanced water tree growth at 65 degrees C is to be due to an enrichment in water at the tip of the growing water tree resulting from water diffusion by dielectrophoresis followed by water condensation under the effect of the electric field.<>
{"title":"Water treeing: interaction between test temperature and other test parameters","authors":"G. Matey, F. Nicoulaz, J. Filippini, Y. Poggi, Ramdane Bouzerara","doi":"10.1109/ICSD.1989.69249","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69249","url":null,"abstract":"The authors discuss complementary studies on the effect of temperature on water tree growth, conducted at two different laboratories, using the same LDPE (low-density polyethylene) reference product at 23 degrees C and 65 degrees C, in a point-to-plane geometry. These very similar tests yielded totally contradictory conclusions on the effect of temperature on water tree growth. In one test the water trees propagated more favourably at 23 degrees C than at 65 degrees C. In the other test the water trees grew larger at 65 degrees C than at 23 degrees C. The latter result has been observed exclusively in the case of a wet grounding environment. As this was the only fundamental difference between the tests, the authors hypothesize that the enhanced water tree growth at 65 degrees C is to be due to an enrichment in water at the tip of the growing water tree resulting from water diffusion by dielectrophoresis followed by water condensation under the effect of the electric field.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116578440","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}
IR spectroscopy, microscopic observations, and breakdown voltage measurements were used to study the influence of additives on physicochemical changes of polypropylene (PP) produced by a corona discharge treatment in air. The untreated film contained a high-temperature antioxidant. The film was treated to remove the antioxidant and then impregnated with an epoxide solution, DGEBA (diglycidylether ether of biphenol A) in cyclohexane. As previously reported, it appears that the changes in the characteristics of corona-treated films occur not only in a surface layer but also at appreciable depths in the polymer. Unsaturation and cross-linking were found together in treated films. The effect of the DGEBA additive is attributed to an increase in the PP reticulation.<>
{"title":"Influence of additives on the ageing of PP films caused by partial discharges","authors":"S. Said, B. Gosse, J. Gosse","doi":"10.1109/ICSD.1989.69241","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69241","url":null,"abstract":"IR spectroscopy, microscopic observations, and breakdown voltage measurements were used to study the influence of additives on physicochemical changes of polypropylene (PP) produced by a corona discharge treatment in air. The untreated film contained a high-temperature antioxidant. The film was treated to remove the antioxidant and then impregnated with an epoxide solution, DGEBA (diglycidylether ether of biphenol A) in cyclohexane. As previously reported, it appears that the changes in the characteristics of corona-treated films occur not only in a surface layer but also at appreciable depths in the polymer. Unsaturation and cross-linking were found together in treated films. The effect of the DGEBA additive is attributed to an increase in the PP reticulation.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"263 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133452101","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}
The authors presents two novel approaches to the assessment of the electrical condition of the HV (high-voltage) insulation in large rotating machines. The first considers the overall condition on the basis of the conduction index, which makes use of the ionic contribution to the electrical conductivity of the HV insulation. The second is concerned with the local aspect defined in terms of a parameter V/sub BF/, which is associated with the concentration of rapid ions at mica/resin or microvoid/resin interfaces. Both are based on an analysis of the physical mechanisms responsible for the slow electrical polarization of the HV insulation and the processes leading up to dielectric breakdown.<>
{"title":"Contribution to the overall and local characterization of the condition of electric ageing of HV insulation in large rotation machines","authors":"J. Dacier, R. Goffaux","doi":"10.1109/ICSD.1989.69267","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69267","url":null,"abstract":"The authors presents two novel approaches to the assessment of the electrical condition of the HV (high-voltage) insulation in large rotating machines. The first considers the overall condition on the basis of the conduction index, which makes use of the ionic contribution to the electrical conductivity of the HV insulation. The second is concerned with the local aspect defined in terms of a parameter V/sub BF/, which is associated with the concentration of rapid ions at mica/resin or microvoid/resin interfaces. Both are based on an analysis of the physical mechanisms responsible for the slow electrical polarization of the HV insulation and the processes leading up to dielectric breakdown.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133052171","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}
The author investigated features of the initiation of a discharge in a gaseous void of small volume, and the influence of a dielectric covering one of the surfaces enclosing a gaseous void on this phenomena. The solid dielectric specimens used were made of: (1) synthetic foil (polyethyleneterephtalate) with a thickness of 20 mu m and surface resistivity rho =10/sup 12/ Omega ; (2) transformer paper with a thickness of 100 mu m and rho =10/sup 10/ Omega ; and (3) transformer-oil-impregnated paper with a thickness of 100 mu m and rho =10/sup 8/ Omega . The use of the dielectric with the higher surface resistivity resulted in an increase of the time lag. A positive-polarity charge on the dielectric surfaces was found to considerably reduce the discharge time lag. The results show that the mechanism of discharge inception in small gas cavities is still not clear. The test results support the hypothesis that in this case the effect of a dielectric electrode coating on the discharge-inception mechanism is decisive. It is further evident that the void-enclosing surface is responsible for the emission intensity of the electrons in the rest time range from 1 to 100 s.<>
{"title":"The effect of a dielectric electrode coating on discharge inception in a gaseous void of small volume","authors":"S. Domaradzka","doi":"10.1109/ICSD.1989.69229","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69229","url":null,"abstract":"The author investigated features of the initiation of a discharge in a gaseous void of small volume, and the influence of a dielectric covering one of the surfaces enclosing a gaseous void on this phenomena. The solid dielectric specimens used were made of: (1) synthetic foil (polyethyleneterephtalate) with a thickness of 20 mu m and surface resistivity rho =10/sup 12/ Omega ; (2) transformer paper with a thickness of 100 mu m and rho =10/sup 10/ Omega ; and (3) transformer-oil-impregnated paper with a thickness of 100 mu m and rho =10/sup 8/ Omega . The use of the dielectric with the higher surface resistivity resulted in an increase of the time lag. A positive-polarity charge on the dielectric surfaces was found to considerably reduce the discharge time lag. The results show that the mechanism of discharge inception in small gas cavities is still not clear. The test results support the hypothesis that in this case the effect of a dielectric electrode coating on the discharge-inception mechanism is decisive. It is further evident that the void-enclosing surface is responsible for the emission intensity of the electrons in the rest time range from 1 to 100 s.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116715955","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}
A. Albini, G. Degli Esposti, F. Guastavino, D. Tommasini
The influence of additives and impurities on conduction and polarization mechanisms in thin films of polypropylene was investigated. It was assumed that the charging current is made up of three components: a polarization component produced by dipole orientation, a conduction current, and a fast transient. The cause of each component was identified by means of a special nonlinear iterative algorithm based on the least-squares method. The results of this investigation show an influence of the additive content and of the temperature on the charging current that can be ascribed to the bulk composition of the materials. It is noted that it is very important to fit the experimental data in order to obtain the correct values of the steady-state conduction currents, which are more significant than the currents obtained at a fixed time.<>
{"title":"Charging phenomena in polypropylene films","authors":"A. Albini, G. Degli Esposti, F. Guastavino, D. Tommasini","doi":"10.1109/ICSD.1989.69178","DOIUrl":"https://doi.org/10.1109/ICSD.1989.69178","url":null,"abstract":"The influence of additives and impurities on conduction and polarization mechanisms in thin films of polypropylene was investigated. It was assumed that the charging current is made up of three components: a polarization component produced by dipole orientation, a conduction current, and a fast transient. The cause of each component was identified by means of a special nonlinear iterative algorithm based on the least-squares method. The results of this investigation show an influence of the additive content and of the temperature on the charging current that can be ascribed to the bulk composition of the materials. It is noted that it is very important to fit the experimental data in order to obtain the correct values of the steady-state conduction currents, which are more significant than the currents obtained at a fixed time.<<ETX>>","PeriodicalId":184126,"journal":{"name":"Proceedings of the 3rd International Conference on Conduction and Breakdown in Solid Dielectrics","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117086502","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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