Pub Date : 2019-10-01DOI: 10.23919/ARWtr.2019.8930186
Yiyi Zhang, Yi Li, Hanbo Zheng, Jiefeng Liu, Chaohai Zhang, Yang Li
The pyrolysis of cellobiose molecular model is simulated by using the molecular dynamics method based on reactive force field (ReaxFF). Studying the generation path of ethanol at the atomic level through a series of ReaxFF-MD simulations. Owing to the molecular systems have hydrogen bonding, fbMC is mixed into ReaxFF to save a lot of sampling waste. In order to ensure the reliability of simulation, the models composed of 40 cellobioses were respectively established for repeated simulation in the range of 500K-3000K. Simulation results show that insulating paper produced ethanol at high temperatures, and the intermediate product of vinyl alcohol is the key to the pyrolysis process. The simulation results are basically consistent with others' previous experiment results, which can provide an effective reference for the use of ethanol as an indicator to evaluate the aging condition of transformers.
{"title":"Molecular Dynamics Simulation on the Generation of Ethanol for Insulating Paper","authors":"Yiyi Zhang, Yi Li, Hanbo Zheng, Jiefeng Liu, Chaohai Zhang, Yang Li","doi":"10.23919/ARWtr.2019.8930186","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930186","url":null,"abstract":"The pyrolysis of cellobiose molecular model is simulated by using the molecular dynamics method based on reactive force field (ReaxFF). Studying the generation path of ethanol at the atomic level through a series of ReaxFF-MD simulations. Owing to the molecular systems have hydrogen bonding, fbMC is mixed into ReaxFF to save a lot of sampling waste. In order to ensure the reliability of simulation, the models composed of 40 cellobioses were respectively established for repeated simulation in the range of 500K-3000K. Simulation results show that insulating paper produced ethanol at high temperatures, and the intermediate product of vinyl alcohol is the key to the pyrolysis process. The simulation results are basically consistent with others' previous experiment results, which can provide an effective reference for the use of ethanol as an indicator to evaluate the aging condition of transformers.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126866848","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930174
M. Naïdjate, N. Bracikowski, M. Hecquet, M. Fratila, M. M. Duró, J. Ducreux
This paper deal with the modeling of large power and distribution transformers by means of reluctance network method. It's about a meshed approach that has the flexibility to fit different transformers topologies. The nonlinear behavior and the coupling with the electrical circuit have been considered. The proposed model has the smartness to estimate accurately the appropriate distributions of the MagnetoMotive Forces (MMF) and the ElectroMotive Forces (EMF) even in the case of eventual defects. The model is generated by MatLab and built automatically under EMTP, which is used as a solver. The obtained results are validated with finite element calculations and with measurements.
{"title":"An intelligent reluctance network model for the study of large power and distribution transformers","authors":"M. Naïdjate, N. Bracikowski, M. Hecquet, M. Fratila, M. M. Duró, J. Ducreux","doi":"10.23919/ARWtr.2019.8930174","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930174","url":null,"abstract":"This paper deal with the modeling of large power and distribution transformers by means of reluctance network method. It's about a meshed approach that has the flexibility to fit different transformers topologies. The nonlinear behavior and the coupling with the electrical circuit have been considered. The proposed model has the smartness to estimate accurately the appropriate distributions of the MagnetoMotive Forces (MMF) and the ElectroMotive Forces (EMF) even in the case of eventual defects. The model is generated by MatLab and built automatically under EMTP, which is used as a solver. The obtained results are validated with finite element calculations and with measurements.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"385 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134258685","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930182
Oasis Sancibrián, C. Vila, I. Fernández, C. Olmo, A. Ortiz
Ester insulating liquids have higher viscosities than mineral oils. This complicates the impregnation of cellulosic insulation and has slowed down the adoption of these dielectrics in high voltage power transformers. This paper studies the dependence of the impregnation characteristics of a mineral oil, a natural ester and a synthetic ester on temperature. For this purpose, impregnation experiments were carried out and the results were compared with an analytical model. The main factors governing the impregnation mechanism related to dielectric liquids are surface tension and viscosity. Results show that increasing the temperature effectively reduces the viscosities of esters, allowing the performance of the esters to approach that of mineral oil. In addition, an exponential model is proposed to predict the impregnation rates associated to a given temperature.
{"title":"Analysis of the Impregnation Process of Cellulosic Materials by Ester-Based Insulating Liquids","authors":"Oasis Sancibrián, C. Vila, I. Fernández, C. Olmo, A. Ortiz","doi":"10.23919/ARWtr.2019.8930182","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930182","url":null,"abstract":"Ester insulating liquids have higher viscosities than mineral oils. This complicates the impregnation of cellulosic insulation and has slowed down the adoption of these dielectrics in high voltage power transformers. This paper studies the dependence of the impregnation characteristics of a mineral oil, a natural ester and a synthetic ester on temperature. For this purpose, impregnation experiments were carried out and the results were compared with an analytical model. The main factors governing the impregnation mechanism related to dielectric liquids are surface tension and viscosity. Results show that increasing the temperature effectively reduces the viscosities of esters, allowing the performance of the esters to approach that of mineral oil. In addition, an exponential model is proposed to predict the impregnation rates associated to a given temperature.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133249708","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930172
L. Rouco, J. Archilla, C. Gavilán
This paper investigates whether existing protection schemes would detect an open phase fault in the start-up power supply system of a 1092 MW Spanish nuclear power generating station. This investigation follows to the 2012 event at unit 2 of Byron station, Illinois, USA. Symmetrical components method is proposed to draw fundamental conclusions. The results of the symmetrical components analysis are validated using EMTP simulations.
{"title":"Open Phase Faults in the Start-up Power Supply System of a Nuclear Power Generating Station","authors":"L. Rouco, J. Archilla, C. Gavilán","doi":"10.23919/ARWtr.2019.8930172","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930172","url":null,"abstract":"This paper investigates whether existing protection schemes would detect an open phase fault in the start-up power supply system of a 1092 MW Spanish nuclear power generating station. This investigation follows to the 2012 event at unit 2 of Byron station, Illinois, USA. Symmetrical components method is proposed to draw fundamental conclusions. The results of the symmetrical components analysis are validated using EMTP simulations.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123749211","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930176
A. Al-Abadi, A. Gamil, F. Schatzl
In the current study, intensive measurements and finite element method (FEM) simulations to optimize the application of magnetic shunts in power transformers are performed. The investigation accounts the effective parameters influencing the magnetic shunts design for the objective of controlling the leakage flux to reduce the generated losses and noise in transformers. Eventually, design rules for the tank and yoke shunts are developed. The developed design tools are applied on case study transformers with different designs, ratings and short circuit impedances. Results show significant reductions in the generated losses and noise during load operation. The study gives the opportunity to optimize the final power transformer design with saving in materials, and therefore the total cost, while the design is still fulfilling the market requirements for both losses and noise.
{"title":"Optimum Shielding Design for Losses and Noise Reduction in Power Transformers","authors":"A. Al-Abadi, A. Gamil, F. Schatzl","doi":"10.23919/ARWtr.2019.8930176","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930176","url":null,"abstract":"In the current study, intensive measurements and finite element method (FEM) simulations to optimize the application of magnetic shunts in power transformers are performed. The investigation accounts the effective parameters influencing the magnetic shunts design for the objective of controlling the leakage flux to reduce the generated losses and noise in transformers. Eventually, design rules for the tank and yoke shunts are developed. The developed design tools are applied on case study transformers with different designs, ratings and short circuit impedances. Results show significant reductions in the generated losses and noise during load operation. The study gives the opportunity to optimize the final power transformer design with saving in materials, and therefore the total cost, while the design is still fulfilling the market requirements for both losses and noise.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"142 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120942016","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930181
C. Engelen, V. Lozano
As part of the energy transition and the associated development of renewable energies, the number of installed dry-type transformers is increasing on the medium-voltage power grid. Therefore, the paper at hand focuses on onsite condition assessment of dry-type power transformers which are often installed in wind turbine nacelles, industrial sites as well as in marine and civil applications. The assessment of the insulation condition is based on an induced voltage test in combination with a partial discharge measurement. In contrast to laboratory tests under controlled conditions, an increased level of interference from rotating machinery, power electronics and other consumers is to be expected on site. The approach of energizing transformers of power ratings up to 15 – 20 MVA with a portable, scalable single-phase voltage source is presented. Due to the single-phase injection the power intake is reduced, and an individual evaluation of each coil becomes possible. Practical examples show how partial discharge signals can be separated from these interferences using a synchronous multi-frequency PD measurement.
{"title":"On-Site Dry-type Power Transformer Condition Assessment based on Partial Discharge Activity","authors":"C. Engelen, V. Lozano","doi":"10.23919/ARWtr.2019.8930181","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930181","url":null,"abstract":"As part of the energy transition and the associated development of renewable energies, the number of installed dry-type transformers is increasing on the medium-voltage power grid. Therefore, the paper at hand focuses on onsite condition assessment of dry-type power transformers which are often installed in wind turbine nacelles, industrial sites as well as in marine and civil applications. The assessment of the insulation condition is based on an induced voltage test in combination with a partial discharge measurement. In contrast to laboratory tests under controlled conditions, an increased level of interference from rotating machinery, power electronics and other consumers is to be expected on site. The approach of energizing transformers of power ratings up to 15 – 20 MVA with a portable, scalable single-phase voltage source is presented. Due to the single-phase injection the power intake is reduced, and an individual evaluation of each coil becomes possible. Practical examples show how partial discharge signals can be separated from these interferences using a synchronous multi-frequency PD measurement.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131585279","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930183
J. M. Rodríguez-Serna, Ricardo Albarracín‐Sánchez, F. Garnacho, F. Álvarez, J. Ortego
Power transformers are key electrical assets in power networks. Their lifetimes are estimated to be around 40 years if they are properly maintained. However, thermal, electrical and mechanical stresses can cause the apparition of partial discharge (PD) activity in the insulation system that can lead to its degradation. Thus, the presence of PD activity can be considered as indicator of failure. Conventional PD acquisitions can be done in accordance with IEC-60270 and IEC-60076-3 standards. In the last decades, unconventional methods, depicted in the IEC-TS-62478 standard, based on acoustic and electromagnetic measurements are being combined with the conventional ones for monitoring power transformers identifying and localizing PD sources. In this paper, the necessity of PD monitoring in power transformers is highlighted and a review of different methods for measuring PD is featured. Besides, some technological trends are depicted. Finally, PD modelling is presented as a promising compliment for PD diagnosis.
{"title":"Partial Discharges Measurements for Condition Monitoring and Diagnosis of Power Transformers: A Review","authors":"J. M. Rodríguez-Serna, Ricardo Albarracín‐Sánchez, F. Garnacho, F. Álvarez, J. Ortego","doi":"10.23919/ARWtr.2019.8930183","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930183","url":null,"abstract":"Power transformers are key electrical assets in power networks. Their lifetimes are estimated to be around 40 years if they are properly maintained. However, thermal, electrical and mechanical stresses can cause the apparition of partial discharge (PD) activity in the insulation system that can lead to its degradation. Thus, the presence of PD activity can be considered as indicator of failure. Conventional PD acquisitions can be done in accordance with IEC-60270 and IEC-60076-3 standards. In the last decades, unconventional methods, depicted in the IEC-TS-62478 standard, based on acoustic and electromagnetic measurements are being combined with the conventional ones for monitoring power transformers identifying and localizing PD sources. In this paper, the necessity of PD monitoring in power transformers is highlighted and a review of different methods for measuring PD is featured. Besides, some technological trends are depicted. Finally, PD modelling is presented as a promising compliment for PD diagnosis.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130310835","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930192
A. Blaszczyk, N. Boulet, M. Buffoni, B. Galletti, C. Pethrick, Wei Wu
This paper presents the coupling of a network model for transformer temperature rise calculation and a CFD model representing the cooling devices consisting of radiator and tank cover. The coupling requires exchange of input data and results between both models, including thermal quantities like temperature and power as well as hydraulic parameters like pressure and mass flow rates. The corresponding interfaces, which allow permanent data exchange during the iterative procedure, are explained and the convergence behavior is analyzed. The results are discussed with respect to differences between models with individual and uniform oil flow in radiator panels as well as models calculated with and without coupling.
{"title":"Coupled CFD-Network Simulations for Cooling of Transformers","authors":"A. Blaszczyk, N. Boulet, M. Buffoni, B. Galletti, C. Pethrick, Wei Wu","doi":"10.23919/ARWtr.2019.8930192","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930192","url":null,"abstract":"This paper presents the coupling of a network model for transformer temperature rise calculation and a CFD model representing the cooling devices consisting of radiator and tank cover. The coupling requires exchange of input data and results between both models, including thermal quantities like temperature and power as well as hydraulic parameters like pressure and mass flow rates. The corresponding interfaces, which allow permanent data exchange during the iterative procedure, are explained and the convergence behavior is analyzed. The results are discussed with respect to differences between models with individual and uniform oil flow in radiator panels as well as models calculated with and without coupling.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133495408","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930187
M. Martinez, J. Pleite
The aim of this document is to present how the interpretation of the RVM (Recovery Voltage Measurement) test can be improved through the use of a Debye equivalent circuit. As it is described in the literature the interpretation of the RVM test requires expertise and if the transformer presents a high interfacial polarization it is not possible to diagnose it in detail. The use of an equivalent Debye circuit modelling the RVM test response allows splitting the different branches which represent different polarization mechanisms. Finally, several case studies are presented, in which it is correlated a dielectric oil treatment carried out and the equivalent circuit changes.
{"title":"Improvement of RVM Test Interpretation Using a Debye Equivalent Circuit","authors":"M. Martinez, J. Pleite","doi":"10.23919/ARWtr.2019.8930187","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930187","url":null,"abstract":"The aim of this document is to present how the interpretation of the RVM (Recovery Voltage Measurement) test can be improved through the use of a Debye equivalent circuit. As it is described in the literature the interpretation of the RVM test requires expertise and if the transformer presents a high interfacial polarization it is not possible to diagnose it in detail. The use of an equivalent Debye circuit modelling the RVM test response allows splitting the different branches which represent different polarization mechanisms. Finally, several case studies are presented, in which it is correlated a dielectric oil treatment carried out and the equivalent circuit changes.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122623840","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 : 2019-10-01DOI: 10.23919/ARWtr.2019.8930189
B. Galletti, A. Blaszczyk, Wei Wu
Based on computational fluid dynamics (CFD) the cooling performance of a typical radiator bank of a liquid-immersed power transformer has been analyzed. The inefficiencies of the original (standard) design have been identified in relation to the unfavorable characteristics of the air flowing through the radiator. Several design changes have been assessed numerically by computing their impact on the cooling capacity of the radiator. This article presents the cooling performance of some of these design solutions, including changes in the radiator panel heights and the addition of a chimney at the top of the radiator. Details of the CFD model are presented along with the air flow patterns and cooling capacities of the enhanced designs compared to the original one.
{"title":"CFD Based Sensitivity Study of Cooling Performance of Transformer Radiators","authors":"B. Galletti, A. Blaszczyk, Wei Wu","doi":"10.23919/ARWtr.2019.8930189","DOIUrl":"https://doi.org/10.23919/ARWtr.2019.8930189","url":null,"abstract":"Based on computational fluid dynamics (CFD) the cooling performance of a typical radiator bank of a liquid-immersed power transformer has been analyzed. The inefficiencies of the original (standard) design have been identified in relation to the unfavorable characteristics of the air flowing through the radiator. Several design changes have been assessed numerically by computing their impact on the cooling capacity of the radiator. This article presents the cooling performance of some of these design solutions, including changes in the radiator panel heights and the addition of a chimney at the top of the radiator. Details of the CFD model are presented along with the air flow patterns and cooling capacities of the enhanced designs compared to the original one.","PeriodicalId":117389,"journal":{"name":"2019 6th International Advanced Research Workshop on Transformers (ARWtr)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122041862","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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