Pub Date : 2002-04-07DOI: 10.1109/ELINSL.2002.995953
L. Centurioni, F. Guastavino, E. Torello
The adoption, in electrical drives, of power supplies equipped with fast electronic devices lead to new "life" problems (e.g. degradation due to partial discharges) which impact on the design of the relevant electric machines insulation systems. Hereby are reported some results of an investigation about the behaviour of thin PET and PI films (polymers adopted in the above insulation systems) after exposure to the action of surface partial discharges (PD) due to PWM-like voltages. The relevant damage after suitable aging (different humidity (RH%) and different PD exposure times) has been examined through of a procedure based on charge decay measurements on the aged films surface. After corona (both positive and negative) charging the films, the surface charge distribution was obtained at different times, so to get the charge decay profiles. The relevant results, depending on films, ambient PD aging conditions, and corona polarity, showed different degrees of correlation between the films surface degradation, the surface charge distribution and the measured charge decay profiles. The latter profiles analysis suggests that this approach can offer complementary information to investigate the PD degradation phenomena that would impact on the insulation systems performance.
{"title":"An investigation about the PD degradation of thin polymer films and its correlation with surface charge decay measurements","authors":"L. Centurioni, F. Guastavino, E. Torello","doi":"10.1109/ELINSL.2002.995953","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995953","url":null,"abstract":"The adoption, in electrical drives, of power supplies equipped with fast electronic devices lead to new \"life\" problems (e.g. degradation due to partial discharges) which impact on the design of the relevant electric machines insulation systems. Hereby are reported some results of an investigation about the behaviour of thin PET and PI films (polymers adopted in the above insulation systems) after exposure to the action of surface partial discharges (PD) due to PWM-like voltages. The relevant damage after suitable aging (different humidity (RH%) and different PD exposure times) has been examined through of a procedure based on charge decay measurements on the aged films surface. After corona (both positive and negative) charging the films, the surface charge distribution was obtained at different times, so to get the charge decay profiles. The relevant results, depending on films, ambient PD aging conditions, and corona polarity, showed different degrees of correlation between the films surface degradation, the surface charge distribution and the measured charge decay profiles. The latter profiles analysis suggests that this approach can offer complementary information to investigate the PD degradation phenomena that would impact on the insulation systems performance.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"64 1","pages":"371-374"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75201038","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995951
M. Pompili, C. Mazzetti
The electrical characteristics of two mineral oils of different viscosity, suitable for use in transformers and switchgears, are compared. It is found that, whereas the higher viscosity oil exhibits greater dielectric losses at more elevated temperatures, it has lower AC and impulse breakdown strength and is characterized by a lower partial discharge inception voltage.
{"title":"Effect of reduced viscosity on the electrical characteristics of transformer and switchgear oils","authors":"M. Pompili, C. Mazzetti","doi":"10.1109/ELINSL.2002.995951","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995951","url":null,"abstract":"The electrical characteristics of two mineral oils of different viscosity, suitable for use in transformers and switchgears, are compared. It is found that, whereas the higher viscosity oil exhibits greater dielectric losses at more elevated temperatures, it has lower AC and impulse breakdown strength and is characterized by a lower partial discharge inception voltage.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"115 1","pages":"363-366"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77040597","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995932
B. Almgren, B. Jacobson, Dong Wu
Since the Pacific HVDC Intertie was commissioned in 1970, measures have been taken to prevent pollution flashovers of the outdoor insulators at the Sylmar West Converter Station. In April 1991, a research program was started with a view to finding the optimum type and layer thickness for different insulator coatings available at the time. Various types and thicknesses of insulator coatings and one type of massive silicone rubber plate were installed, together with bare porcelain plates as references, on test racks at the station. Annual inspections were performed the first three years and the last one after 10 years of exposure. The following conclusions may be drawn from the research program. Most plates coated with silicone grease of three different types and in three different layer thicknesses were still water repellent after 10 years of exposure. The massive silicone rubber plate and one out of three RTV coatings also showed good performance, while the other two types of silicone rubber coating had become wetter. Silicone greases performed better than other coatings in this test. A thin layer of coating, e.g. 0.5-1 mm, is sufficient for good long-term performance.
{"title":"Long term evaluation of insulator coatings at one of the Pacific Intertie HVDC converter stations","authors":"B. Almgren, B. Jacobson, Dong Wu","doi":"10.1109/ELINSL.2002.995932","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995932","url":null,"abstract":"Since the Pacific HVDC Intertie was commissioned in 1970, measures have been taken to prevent pollution flashovers of the outdoor insulators at the Sylmar West Converter Station. In April 1991, a research program was started with a view to finding the optimum type and layer thickness for different insulator coatings available at the time. Various types and thicknesses of insulator coatings and one type of massive silicone rubber plate were installed, together with bare porcelain plates as references, on test racks at the station. Annual inspections were performed the first three years and the last one after 10 years of exposure. The following conclusions may be drawn from the research program. Most plates coated with silicone grease of three different types and in three different layer thicknesses were still water repellent after 10 years of exposure. The massive silicone rubber plate and one out of three RTV coatings also showed good performance, while the other two types of silicone rubber coating had become wetter. Silicone greases performed better than other coatings in this test. A thin layer of coating, e.g. 0.5-1 mm, is sufficient for good long-term performance.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"9 1","pages":"285-289"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77134117","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995956
Han-Goo Cho, U. Lee, Seok-Su Kim, Young-Don Park
In this paper, the temperature distribution and thermal stress analysis of 50 kVA pole cast resin transformer for power distribution are investigated by FEM program. The temperature change according to load rates of transformer and thermal stress have also been investigated.
{"title":"The temperature distribution and thermal stress analysis of pole cast resin transformer for power distribution","authors":"Han-Goo Cho, U. Lee, Seok-Su Kim, Young-Don Park","doi":"10.1109/ELINSL.2002.995956","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995956","url":null,"abstract":"In this paper, the temperature distribution and thermal stress analysis of 50 kVA pole cast resin transformer for power distribution are investigated by FEM program. The temperature change according to load rates of transformer and thermal stress have also been investigated.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"11 1","pages":"384-386"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84967661","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995945
S. Finke, D. Koenig
This paper presents the results of tests to evaluate the effects of high current fault arcs occurring in electrical switchgear compartments stressing insulating walls made of different materials. These partitions are stressed mechanically and thermally. Additionally, a new effect is found which is described in this paper.
{"title":"Recent investigations on high current internal arcs in low voltage switchgear","authors":"S. Finke, D. Koenig","doi":"10.1109/ELINSL.2002.995945","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995945","url":null,"abstract":"This paper presents the results of tests to evaluate the effects of high current fault arcs occurring in electrical switchgear compartments stressing insulating walls made of different materials. These partitions are stressed mechanically and thermally. Additionally, a new effect is found which is described in this paper.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"66 1","pages":"336-340"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83107889","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995875
G. Coletti, F. Guastavino, E. Torello
The present work is part of a research program aimed at studying the long-term performance of electric motor insulation systems which are part of modern drives (equipped with fast inverters/converters). In particular the degradation effects of partial discharges (PD) were here experimentally studied. Different (purposely selected and generated) PWM-like waveform voltages have been applied to twisted pairs (polyimide-imide enamelled wires) specimens. The tests have been carried out at 100/spl deg/C. The relevant PD output (patterns) has been recorded by means of a digital system and the times-to-breakdown of the specimens have been recorded. The various PD patterns appeared consistent with the recorded lifetimes and the planned study has produced both an innovative line of approach and interesting results.
{"title":"Influence of different square voltage waveforms on the partial discharges behaviour during tests on twisted pair specimens","authors":"G. Coletti, F. Guastavino, E. Torello","doi":"10.1109/ELINSL.2002.995875","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995875","url":null,"abstract":"The present work is part of a research program aimed at studying the long-term performance of electric motor insulation systems which are part of modern drives (equipped with fast inverters/converters). In particular the degradation effects of partial discharges (PD) were here experimentally studied. Different (purposely selected and generated) PWM-like waveform voltages have been applied to twisted pairs (polyimide-imide enamelled wires) specimens. The tests have been carried out at 100/spl deg/C. The relevant PD output (patterns) has been recorded by means of a digital system and the times-to-breakdown of the specimens have been recorded. The various PD patterns appeared consistent with the recorded lifetimes and the planned study has produced both an innovative line of approach and interesting results.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"8 1","pages":"36-39"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86700014","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995966
F. Wang, Q. Zhang, Y. Qiu, E. Kuffel
The phenomena of surface charging are investigated using the capacitive probe method. In order to decrease the charge leakage a new type probe with high resolution is designed. The influence of voltage amplitude, duration, polarity and surrounding humidity on the surface charging are studied. The accumulation competition between positive charges and negative charges is observed. The experimental results show that at different places on the insulator surface the surface charging has different saturation time constants.
{"title":"Insulator surface charge accumulation under DC voltage","authors":"F. Wang, Q. Zhang, Y. Qiu, E. Kuffel","doi":"10.1109/ELINSL.2002.995966","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995966","url":null,"abstract":"The phenomena of surface charging are investigated using the capacitive probe method. In order to decrease the charge leakage a new type probe with high resolution is designed. The influence of voltage amplitude, duration, polarity and surrounding humidity on the surface charging are studied. The accumulation competition between positive charges and negative charges is observed. The experimental results show that at different places on the insulator surface the surface charging has different saturation time constants.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"11 1","pages":"426-429"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74499536","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995915
A. El-Hag, S. Jayaram, E. Cherney
This paper presents the results of using the low frequency harmonics of leakage current as a measure of dry band arcing in salt-fog. Sleeved high temperature vulcanized (HTV) silicone rubber rods were tested under 0.25, 0.40 and 0.60 kV/cm in salt-fog at two different salinities, i.e. 1000 and 2500 /spl mu/S/cm. The leakage current was measured and analyzed using fast Fourier transform (FFT). The results show that as the electric field increases, the fundamental component of the leakage current decreases and both the third and fifth harmonic components increase. Also, increasing the salinity of the fog increases both the third and fifth harmonic components with no significant change in the fundamental component. In general, harmonic components increased only when arcing occurred; thus providing a signature for the dry band arcing activities.
{"title":"Use of low frequency harmonic components as a signature to detect arcing on HTV silicone rubber in salt-fog","authors":"A. El-Hag, S. Jayaram, E. Cherney","doi":"10.1109/ELINSL.2002.995915","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995915","url":null,"abstract":"This paper presents the results of using the low frequency harmonics of leakage current as a measure of dry band arcing in salt-fog. Sleeved high temperature vulcanized (HTV) silicone rubber rods were tested under 0.25, 0.40 and 0.60 kV/cm in salt-fog at two different salinities, i.e. 1000 and 2500 /spl mu/S/cm. The leakage current was measured and analyzed using fast Fourier transform (FFT). The results show that as the electric field increases, the fundamental component of the leakage current decreases and both the third and fifth harmonic components increase. Also, increasing the salinity of the fog increases both the third and fifth harmonic components with no significant change in the fundamental component. In general, harmonic components increased only when arcing occurred; thus providing a signature for the dry band arcing activities.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"35 1","pages":"212-215"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76134994","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995982
R. Mills, C. Payne, K. Younsi
Epoxy resins and micaceous insulation systems are used to insulate high voltage large rotating machine components. Composite insulation systems undergo marked changes in dielectric response as the cure of the system progresses. It is possible to exploit these changes to monitor and optimize the curing process. This paper presents the first of some work done on the global insulation cure monitoring of large AC motor stator windings processed through global vacuum pressure impregnation (VPI). Changes in the measured permittivity and dissipation factor in the range of 1 Hz to 10 kHz for laboratory samples, as well as capacitance test results on full size stators at 100 Hz, are reported. It is shown that permittivity (capacitance) appears to be ideal for cure monitoring purposes. It is also shown that the best frequencies for monitoring of this type are in the 100 Hz to 500 Hz range. Changes in the slope of the natural logarithm of permittivity (capacitance) with time (d[Ln(/spl epsi/')]/dt) are shown to be promising as an indicator of the level of cure. By terminating the curing when d[Ln(/spl epsi/')]/dt reaches a certain terminal value, it is believed that a high level of reproducibility in the level of cure of the resulting insulation system can be achieved. Discussion is given on analyses of d[Ln(/spl epsi/')]/dt, both in the laboratory and in the factory. The level of cure should also be correlated to other relevant physical properties such as the glass transition temperature or other global mechanical properties. It is shown how dielectric properties monitoring optimizes global VPI processing by producing a more reliable level of cure and reducing cure time.
{"title":"Insulation cure monitoring on global VPI large AC motors","authors":"R. Mills, C. Payne, K. Younsi","doi":"10.1109/ELINSL.2002.995982","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995982","url":null,"abstract":"Epoxy resins and micaceous insulation systems are used to insulate high voltage large rotating machine components. Composite insulation systems undergo marked changes in dielectric response as the cure of the system progresses. It is possible to exploit these changes to monitor and optimize the curing process. This paper presents the first of some work done on the global insulation cure monitoring of large AC motor stator windings processed through global vacuum pressure impregnation (VPI). Changes in the measured permittivity and dissipation factor in the range of 1 Hz to 10 kHz for laboratory samples, as well as capacitance test results on full size stators at 100 Hz, are reported. It is shown that permittivity (capacitance) appears to be ideal for cure monitoring purposes. It is also shown that the best frequencies for monitoring of this type are in the 100 Hz to 500 Hz range. Changes in the slope of the natural logarithm of permittivity (capacitance) with time (d[Ln(/spl epsi/')]/dt) are shown to be promising as an indicator of the level of cure. By terminating the curing when d[Ln(/spl epsi/')]/dt reaches a certain terminal value, it is believed that a high level of reproducibility in the level of cure of the resulting insulation system can be achieved. Discussion is given on analyses of d[Ln(/spl epsi/')]/dt, both in the laboratory and in the factory. The level of cure should also be correlated to other relevant physical properties such as the glass transition temperature or other global mechanical properties. It is shown how dielectric properties monitoring optimizes global VPI processing by producing a more reliable level of cure and reducing cure time.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"62 1","pages":"492-496"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73488923","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 : 2002-04-07DOI: 10.1109/ELINSL.2002.995986
A. Cavallini, M. Conti, G. Montanari, A. Contin
This paper presents results of tests having the purpose to derive indexes, from PD measurements, which can enable the recognition of PD generated from different sources, such as internal voids, surface and corona discharges. Moreover, recognition of the location and shape of cavities can be achieved. PD measurements are performed by a digital instrument which allows PD-pulse amplitude, phase and shape to be recorded. Such results can be employed to improve recognition efficiency of PD-based diagnostic tools used for on field applications.
{"title":"Indexes for the recognition of insulation system defects derived from partial discharge measurements","authors":"A. Cavallini, M. Conti, G. Montanari, A. Contin","doi":"10.1109/ELINSL.2002.995986","DOIUrl":"https://doi.org/10.1109/ELINSL.2002.995986","url":null,"abstract":"This paper presents results of tests having the purpose to derive indexes, from PD measurements, which can enable the recognition of PD generated from different sources, such as internal voids, surface and corona discharges. Moreover, recognition of the location and shape of cavities can be achieved. PD measurements are performed by a digital instrument which allows PD-pulse amplitude, phase and shape to be recorded. Such results can be employed to improve recognition efficiency of PD-based diagnostic tools used for on field applications.","PeriodicalId":10532,"journal":{"name":"Conference Record of the the 2002 IEEE International Symposium on Electrical Insulation (Cat. No.02CH37316)","volume":"28 1","pages":"511-515"},"PeriodicalIF":0.0,"publicationDate":"2002-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89552836","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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