Pub Date : 2018-06-01DOI: 10.1109/EIC.2018.8481019
A. Staubach, G. Schmidt, F. Pohlmann, H. Hirsch
An essential component of the insulation system of large electric machines is the corona protection system. One important parameter in particular of the outer corona protection (OCP) is the ohmic resistance together with service related current and potential distributions as well as locally generated power losses. These parameters can be calculated and analyzed using finite element method (FEM). In this study the influence of the OCP material parameters on the electric field distributions in the insulation system are investigated. Real wrapped insulation system structures are modeled with a high level of detail by consideration of anisotropic material characteristics. A new approach to assess the ideal anisotropic OCP material properties is introduced with the process of the swarm optimization algorithm. The results of these examinations are used for the development of an ideal OCP system with the aim to minimize the electric and thermal field stresses in the insulation system. The results for one particular machine type are evaluated by analyzing the solution data to characterize the overall general OCP system behavior.
{"title":"Investigation of Ideal Anisotropic Material Properties for Outer Corona Protection Systems in Large Rotating Machines","authors":"A. Staubach, G. Schmidt, F. Pohlmann, H. Hirsch","doi":"10.1109/EIC.2018.8481019","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481019","url":null,"abstract":"An essential component of the insulation system of large electric machines is the corona protection system. One important parameter in particular of the outer corona protection (OCP) is the ohmic resistance together with service related current and potential distributions as well as locally generated power losses. These parameters can be calculated and analyzed using finite element method (FEM). In this study the influence of the OCP material parameters on the electric field distributions in the insulation system are investigated. Real wrapped insulation system structures are modeled with a high level of detail by consideration of anisotropic material characteristics. A new approach to assess the ideal anisotropic OCP material properties is introduced with the process of the swarm optimization algorithm. The results of these examinations are used for the development of an ideal OCP system with the aim to minimize the electric and thermal field stresses in the insulation system. The results for one particular machine type are evaluated by analyzing the solution data to characterize the overall general OCP system behavior.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129519370","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481093
R. Foster, Volney Naranjo, Daniel Carreño
High voltage circuit breakers have traditionally been tested with at least one side of the contacts disconnected from ground. This has mainly been due to the challenges that arise when trying to test a circuit breaker with both sides grounded. Although this has been the accepted practice for many years, it has always put the test engineers or technicians at an increased safety risk. In order to perform circuit breaker timing under safer conditions, different methods of testing with both sides grounded have been developed using various technologies. This paper will explore Dynamic Capacitance Measurements (DCM) as a method for timing circuit breakers. DCM uses a variable high frequency source to find the path of least impedance within a parallel circuit of the circuit breaker and ground, as well as establishing resonant points that change depending on whether or not the circuit breaker is open or closed. If these resonance points are monitored while the circuit breaker is operated, accurate contact open and close times can be measured safely and efficiently. The basic functionality of dynamic capacitance measurements and how they can be applied to both air insulated and gas insulated switchgear will be explored along with case studies and comparisons to traditional testing.
{"title":"Testing High Voltage Circuit Breakers with Both Sides Grounded Using Dynamic Capacitance (DCM) Technology","authors":"R. Foster, Volney Naranjo, Daniel Carreño","doi":"10.1109/EIC.2018.8481093","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481093","url":null,"abstract":"High voltage circuit breakers have traditionally been tested with at least one side of the contacts disconnected from ground. This has mainly been due to the challenges that arise when trying to test a circuit breaker with both sides grounded. Although this has been the accepted practice for many years, it has always put the test engineers or technicians at an increased safety risk. In order to perform circuit breaker timing under safer conditions, different methods of testing with both sides grounded have been developed using various technologies. This paper will explore Dynamic Capacitance Measurements (DCM) as a method for timing circuit breakers. DCM uses a variable high frequency source to find the path of least impedance within a parallel circuit of the circuit breaker and ground, as well as establishing resonant points that change depending on whether or not the circuit breaker is open or closed. If these resonance points are monitored while the circuit breaker is operated, accurate contact open and close times can be measured safely and efficiently. The basic functionality of dynamic capacitance measurements and how they can be applied to both air insulated and gas insulated switchgear will be explored along with case studies and comparisons to traditional testing.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130877437","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481118
G. Montanari, P. Seri, A. Contin
There are two thought trends concerning partial discharge, PD, measurements and diagnostics in electrical insulation systems. One is make it simple and refer to PD amplitude and repetition rate. The other is try to identify the typologies of discharges and focus on each type of source generating PD for diagnostic and maintenance decisions. In this paper, an approach towards the determination of a health index for rotating machines is presented. It is based on the harmfulness of typical defects able to generate PD and, hence, on the capability of the detection system (sensor, filters, PD detector, software) to provide efficient noise rejection and/or noise and PD source identification. The output, that is, the global health index, is thought to be helpful to support maintenance manager decisions about the actions which may be needed to keep reliability of a rotating machine at the desired level, and also to evaluate in terms of cost/effectiveness the potential maintenance actions.
{"title":"How to Deal with the Severity of Different Partial Discharge Sources in Rotating Machines: The Definition of a New Health Index","authors":"G. Montanari, P. Seri, A. Contin","doi":"10.1109/EIC.2018.8481118","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481118","url":null,"abstract":"There are two thought trends concerning partial discharge, PD, measurements and diagnostics in electrical insulation systems. One is make it simple and refer to PD amplitude and repetition rate. The other is try to identify the typologies of discharges and focus on each type of source generating PD for diagnostic and maintenance decisions. In this paper, an approach towards the determination of a health index for rotating machines is presented. It is based on the harmfulness of typical defects able to generate PD and, hence, on the capability of the detection system (sensor, filters, PD detector, software) to provide efficient noise rejection and/or noise and PD source identification. The output, that is, the global health index, is thought to be helpful to support maintenance manager decisions about the actions which may be needed to keep reliability of a rotating machine at the desired level, and also to evaluate in terms of cost/effectiveness the potential maintenance actions.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115261830","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481059
J. Borghetto, G. Pirovano, C. Tornelli, A. Contin
The experimental set-up and the first results of PD measurements performed to evaluate different types of MV cable-joints under electrical and thermal stresses, are discussed in the paper. Twelve cables equipped with different types of joints were connected together to form a ring in short-circuit. The ring was enegized at rated voltage and current. Cycles of temperature having a period of one day have been applied by controlling the current by means of external coils. PD were monitored during the heating and cooling of the cables. Problems related to calibration and signal interference between the different cables, have been examined. The PD inception and the evolution of PD patterns due to the formation of defects in some joints, are discussed.
{"title":"Test Set-Up and Preliminary Results of PD Measurements Performed During Thermal Cycles Applied to Different Types of MV Cable Joints","authors":"J. Borghetto, G. Pirovano, C. Tornelli, A. Contin","doi":"10.1109/EIC.2018.8481059","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481059","url":null,"abstract":"The experimental set-up and the first results of PD measurements performed to evaluate different types of MV cable-joints under electrical and thermal stresses, are discussed in the paper. Twelve cables equipped with different types of joints were connected together to form a ring in short-circuit. The ring was enegized at rated voltage and current. Cycles of temperature having a period of one day have been applied by controlling the current by means of external coils. PD were monitored during the heating and cooling of the cables. Problems related to calibration and signal interference between the different cables, have been examined. The PD inception and the evolution of PD patterns due to the formation of defects in some joints, are discussed.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123930597","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 : 2018-06-01DOI: 10.1109/EIC.2018.8480896
J. Lauletta, Jose Alexis De Abrue-Gaarcia, Y. Sozer, Awab A. Ali
Electric utilities and heavy industry are experiencing increased insulated cable failures in low-voltage networks and medium-voltage circuit applications with catastrophic results. Cables that have been operating more than 50-years in direct buried, conduit, and metal raceway schemes fail for a variety of reasons. Time and heat are the chief contributors to insulation failure. Cables are difficult and dangerous to test because most test techniques require that the cable be taken out of service, disconnected, and often evaluated with destructive test signals. Older cables that should be tested may be skipped as the disconnection and movement of the cable in preparation for invasive testing can cause insulation mechanical failure. A nondestructive, non -invasive test technology that is applied to operating cables in a variety of applications is reviewed. The direct-reading insulation condition assessment technology induces non-destructive signals in the operating conductor. The technology evaluates the condition of cable insulation, insulators that suspend or support non-insulated conductors, and is useful in locating separations of concentric neutrals in jacketed and non-jacketed cables. The technology is also helpful in identifying cable phasing. Unique attributes of the technology allow for the test of entire circuits or segments of circuits without altering the operating system. Field test scenarios and test results are presented along with a technology overview.
{"title":"The Direct Condition Assessment of Operating Low-Voltage Insulated Cables","authors":"J. Lauletta, Jose Alexis De Abrue-Gaarcia, Y. Sozer, Awab A. Ali","doi":"10.1109/EIC.2018.8480896","DOIUrl":"https://doi.org/10.1109/EIC.2018.8480896","url":null,"abstract":"Electric utilities and heavy industry are experiencing increased insulated cable failures in low-voltage networks and medium-voltage circuit applications with catastrophic results. Cables that have been operating more than 50-years in direct buried, conduit, and metal raceway schemes fail for a variety of reasons. Time and heat are the chief contributors to insulation failure. Cables are difficult and dangerous to test because most test techniques require that the cable be taken out of service, disconnected, and often evaluated with destructive test signals. Older cables that should be tested may be skipped as the disconnection and movement of the cable in preparation for invasive testing can cause insulation mechanical failure. A nondestructive, non -invasive test technology that is applied to operating cables in a variety of applications is reviewed. The direct-reading insulation condition assessment technology induces non-destructive signals in the operating conductor. The technology evaluates the condition of cable insulation, insulators that suspend or support non-insulated conductors, and is useful in locating separations of concentric neutrals in jacketed and non-jacketed cables. The technology is also helpful in identifying cable phasing. Unique attributes of the technology allow for the test of entire circuits or segments of circuits without altering the operating system. Field test scenarios and test results are presented along with a technology overview.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131631942","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481102
Ricarda Wagner, J. Bauer, Bastian Plochmann, Steffen Lang, D. Schönauer-Kamin, R. Moos
Antimony doped tin oxide, a known gas sensing material, is investigated as a possible substitute for carbon black as filler for outer corona protection systems. Therefore it is necessary to prove the stability of electrical resistance and reversibility during exposure to discharge products like UV-radiation, ozone and NO2. Furthermore, the location of air-cooled generators can vary and with it the surrounding atmosphere, for example humidity. Samples of particle filled resin films are prepared and the resistance is measured while exposed to different diluted gases (varying O2, H2, humidity and NO2in the gas atmosphere at 100 °C). The resistance changes with varying O2 (%-range) and NO2(ppm-range) concentrations. These effects are enhanced by UV-radiation (365 nm). All measured resistance changes are reversible but there is a long relaxation time. Besides, both the matrix material and the particle geometry of the Sb-doped SnO2were changed. It was found that the resistance stability depends on the combination of matrix material and particle geometry. We found a link between resistance change and surface roughness, whereby a smoother surface seems to be more stable. The influence of ozone on the film resistance was also measured: Small amounts of ozone (< 1 ppm) do not change the resistance of a compound film during ten days at room temperature. Hence, it is concluded that antimony-doped-SrrOa-compound-Illms are stable against different gas species and UV-light. However, it is important to choose a proper particle-resin combination for a smooth surface resulting in improved resistance stability.
{"title":"Effect of Ambient Conditions on the Resistance of Metal Oxides as a Novel Material for Outer Corona Protection Systems","authors":"Ricarda Wagner, J. Bauer, Bastian Plochmann, Steffen Lang, D. Schönauer-Kamin, R. Moos","doi":"10.1109/EIC.2018.8481102","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481102","url":null,"abstract":"Antimony doped tin oxide, a known gas sensing material, is investigated as a possible substitute for carbon black as filler for outer corona protection systems. Therefore it is necessary to prove the stability of electrical resistance and reversibility during exposure to discharge products like UV-radiation, ozone and NO2. Furthermore, the location of air-cooled generators can vary and with it the surrounding atmosphere, for example humidity. Samples of particle filled resin films are prepared and the resistance is measured while exposed to different diluted gases (varying O2, H2, humidity and NO2in the gas atmosphere at 100 °C). The resistance changes with varying O2 (%-range) and NO2(ppm-range) concentrations. These effects are enhanced by UV-radiation (365 nm). All measured resistance changes are reversible but there is a long relaxation time. Besides, both the matrix material and the particle geometry of the Sb-doped SnO2were changed. It was found that the resistance stability depends on the combination of matrix material and particle geometry. We found a link between resistance change and surface roughness, whereby a smoother surface seems to be more stable. The influence of ozone on the film resistance was also measured: Small amounts of ozone (< 1 ppm) do not change the resistance of a compound film during ten days at room temperature. Hence, it is concluded that antimony-doped-SrrOa-compound-Illms are stable against different gas species and UV-light. However, it is important to choose a proper particle-resin combination for a smooth surface resulting in improved resistance stability.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134054847","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481120
W. Thansiphraserth, P. Lewin
Partial Discharge (PD) measurements are an important tool for assessment of the condition of the insulation systems of power equipment such as high voltage transformers. One of the most dangerous failure modes in a large autotransformer is due to surface discharge along the interphase barrier board. Previous work has shown the measurement of Phase Resolved Partial Discharge, PRPD, patterns of surface tracking using either a local PD source only or for a local PD source in the presence of an additional single phase electric field. More recently, results obtained for a barrier board with 9% moisture content in the presence of a two phase applied field as well as a PD source have been reported. In this paper, experiments are described using two phase applied fields for samples with different moisture content of 3% and 6%. The experimental results and discussion highlight the effect of different moisture content within pressboards under the effect of two phase energization, on surface charge behavior. The results should assist in determining the effect of moisture content on PRPD patterns and will help to improve diagnostics of field data captured in real-time. The experiments have been undertaken at the Tony Davies High Voltage Laboratory, University of Southampton.
{"title":"Surface Tracking Along the Interphase Barrier of a Large Transformer: Effect of Moisture within Barrier Board","authors":"W. Thansiphraserth, P. Lewin","doi":"10.1109/EIC.2018.8481120","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481120","url":null,"abstract":"Partial Discharge (PD) measurements are an important tool for assessment of the condition of the insulation systems of power equipment such as high voltage transformers. One of the most dangerous failure modes in a large autotransformer is due to surface discharge along the interphase barrier board. Previous work has shown the measurement of Phase Resolved Partial Discharge, PRPD, patterns of surface tracking using either a local PD source only or for a local PD source in the presence of an additional single phase electric field. More recently, results obtained for a barrier board with 9% moisture content in the presence of a two phase applied field as well as a PD source have been reported. In this paper, experiments are described using two phase applied fields for samples with different moisture content of 3% and 6%. The experimental results and discussion highlight the effect of different moisture content within pressboards under the effect of two phase energization, on surface charge behavior. The results should assist in determining the effect of moisture content on PRPD patterns and will help to improve diagnostics of field data captured in real-time. The experiments have been undertaken at the Tony Davies High Voltage Laboratory, University of Southampton.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132961011","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 : 2018-06-01DOI: 10.1109/EIC.2018.8480884
Jens-Michael Löwe, V. Hinrichsen, C. Tropea
Sessile water droplets on insulating surfaces influence the ageing behavior of the insulating material, especially for composite insulators, which are covered by silicone rubber. The hydrophobic silicone surface causes the formation of high contact angles of sessile droplets, which leads to local enhancement of the electric field directly at the contact line. The enhanced electric field can cause partial discharges, which deteriorate the surface properties and enhance ageing of the surface. During operation, beside the constant stress by AC or DC voltage, composite insulators are exposed to different transient electrical stresses like switching or lightning impulse voltages. In this paper the impact of switching and lightning impulse voltage on multiple droplets is investigated to improve the understanding of the interaction between the droplets and the electric field, especially during operation. The behavior of multiple droplets is investigated in dependence on droplet-droplet distance, droplet volume as well as the applied voltage amplitude. Depending on the boundary conditions, three different regimes for multiple droplet interaction are identified: coalescence of droplets, vibration or movement of the individual droplets without coalescence and no interaction. Thereby, the investigation improves the understanding of the behavior of sessile droplets as well as the interaction of several droplets exposed to transient electric fields, and thus the understanding of ageing mechanisms of composite insulators.
{"title":"Droplet Behavior Under the Impact of Lightning and Switching Impulse Voltage","authors":"Jens-Michael Löwe, V. Hinrichsen, C. Tropea","doi":"10.1109/EIC.2018.8480884","DOIUrl":"https://doi.org/10.1109/EIC.2018.8480884","url":null,"abstract":"Sessile water droplets on insulating surfaces influence the ageing behavior of the insulating material, especially for composite insulators, which are covered by silicone rubber. The hydrophobic silicone surface causes the formation of high contact angles of sessile droplets, which leads to local enhancement of the electric field directly at the contact line. The enhanced electric field can cause partial discharges, which deteriorate the surface properties and enhance ageing of the surface. During operation, beside the constant stress by AC or DC voltage, composite insulators are exposed to different transient electrical stresses like switching or lightning impulse voltages. In this paper the impact of switching and lightning impulse voltage on multiple droplets is investigated to improve the understanding of the interaction between the droplets and the electric field, especially during operation. The behavior of multiple droplets is investigated in dependence on droplet-droplet distance, droplet volume as well as the applied voltage amplitude. Depending on the boundary conditions, three different regimes for multiple droplet interaction are identified: coalescence of droplets, vibration or movement of the individual droplets without coalescence and no interaction. Thereby, the investigation improves the understanding of the behavior of sessile droplets as well as the interaction of several droplets exposed to transient electric fields, and thus the understanding of ageing mechanisms of composite insulators.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134456801","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481063
A. Sbravati, M. H. Oka, Jair Anísio Maso, Jeff Valmus
The limited loadability of mineral oil filled transformers leads the users to select the transformer size necessary to meet the required peak demand; this causes the nominal rating to be higher than necessary for the typical demand resulting in transformers that have low annual average loading. The association of a transformer using high temperature insulation system, having both the solid (thermally upgraded Kraft paper) and liquid insulation (natural ester dielectric liquid) thermal classes higher than conventional, with the strategy of defining the nominal rating based on the conventional temperature rise limits lead to transformers holding a “reserve capacity”. This significant additional capacity without accelerated life consumption of the paper and no oil degradation enhances the loadability of the transformers and can be used to handle yearly peak demand by means of a smaller transformer. Brazilian utility CELESC adopted this concept for twelve natural ester filled transformers, which were installed and monitored in service for a period of one year. The reduction of the no-load losses of the smaller transformer resulted in 22.7% reduction of total dissipated energy in the period. Detailed results are presented in this study. Besides the advantage of improving system efficiency, the reduction of the nominal rating of the transformers also brings savings in transformer purchasing, and reduces environmental impact, mitigates the risk of fire, which are important issues for the utility.
{"title":"Enhancing Transformers Loadability for Optimizing Assets Utilization and Efficiency","authors":"A. Sbravati, M. H. Oka, Jair Anísio Maso, Jeff Valmus","doi":"10.1109/EIC.2018.8481063","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481063","url":null,"abstract":"The limited loadability of mineral oil filled transformers leads the users to select the transformer size necessary to meet the required peak demand; this causes the nominal rating to be higher than necessary for the typical demand resulting in transformers that have low annual average loading. The association of a transformer using high temperature insulation system, having both the solid (thermally upgraded Kraft paper) and liquid insulation (natural ester dielectric liquid) thermal classes higher than conventional, with the strategy of defining the nominal rating based on the conventional temperature rise limits lead to transformers holding a “reserve capacity”. This significant additional capacity without accelerated life consumption of the paper and no oil degradation enhances the loadability of the transformers and can be used to handle yearly peak demand by means of a smaller transformer. Brazilian utility CELESC adopted this concept for twelve natural ester filled transformers, which were installed and monitored in service for a period of one year. The reduction of the no-load losses of the smaller transformer resulted in 22.7% reduction of total dissipated energy in the period. Detailed results are presented in this study. Besides the advantage of improving system efficiency, the reduction of the nominal rating of the transformers also brings savings in transformer purchasing, and reduces environmental impact, mitigates the risk of fire, which are important issues for the utility.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133900910","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 : 2018-06-01DOI: 10.1109/EIC.2018.8481047
A. Esfahani, S. Shahabi, G. Stone, B. Kordi
The rapid growth of electric apparatus in the more electric aircraft (MEA) causes the necessity to step up the electrical power. This, in turn, requires to a higher voltage which increases the electrical stress on insulation system. This can cause partial discharge (PD) in aircraft insulation system. Also, the aircraft generator provides electrical power with variable frequency. The insulation system of aircraft generator experiences different range of air pressure levels under variable voltage frequency. There is an interest on partial discharge detection under this condition. This paper presents the experimental tests that have been conducted to study the impact of voltage frequency and air pressure on corona PD pulse characteristics.
{"title":"Investigation of Corona Partial Discharge Characteristics Under Variable Frequency and Air Pressure","authors":"A. Esfahani, S. Shahabi, G. Stone, B. Kordi","doi":"10.1109/EIC.2018.8481047","DOIUrl":"https://doi.org/10.1109/EIC.2018.8481047","url":null,"abstract":"The rapid growth of electric apparatus in the more electric aircraft (MEA) causes the necessity to step up the electrical power. This, in turn, requires to a higher voltage which increases the electrical stress on insulation system. This can cause partial discharge (PD) in aircraft insulation system. Also, the aircraft generator provides electrical power with variable frequency. The insulation system of aircraft generator experiences different range of air pressure levels under variable voltage frequency. There is an interest on partial discharge detection under this condition. This paper presents the experimental tests that have been conducted to study the impact of voltage frequency and air pressure on corona PD pulse characteristics.","PeriodicalId":184139,"journal":{"name":"2018 IEEE Electrical Insulation Conference (EIC)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132864949","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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