Pub Date : 2018-09-01DOI: 10.1109/CMD.2018.8535600
Ying Du, Qingzhu Shao, Yadong Liu, G. Sheng, X. Jiang
Fault feature extraction is critical for fault line detection, but difficult to be effective and robust. Unbalanced characteristics of the fault signal sample will make feature extraction more difficult. A novel method using Choi- Williams time-frequency distribution based convolutional neural network and task decomposition framework was proposed. Choi- Williams time-frequency analysis was applied to generate time-frequency distribution image of fault signal. Then, convolutional neural network (CNN) was trained by a lot of time-frequency distribution images generated under different fault conditions. CNN can extract features of the time-frequency distribution image adaptively and select the fault line. The task decomposition framework was first proposed to solve the problem of unbalanced fault signal sample for better feature extraction. A resonant grounding distribution system is simulated to verify this method under different fault conditions and the results showed the detection of the single line-to-ground fault is more accurate.
{"title":"Detection of Single Line-to-Ground Fault Using Convolutional Neural Network and Task Decomposition Framework in Distribution Systems","authors":"Ying Du, Qingzhu Shao, Yadong Liu, G. Sheng, X. Jiang","doi":"10.1109/CMD.2018.8535600","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535600","url":null,"abstract":"Fault feature extraction is critical for fault line detection, but difficult to be effective and robust. Unbalanced characteristics of the fault signal sample will make feature extraction more difficult. A novel method using Choi- Williams time-frequency distribution based convolutional neural network and task decomposition framework was proposed. Choi- Williams time-frequency analysis was applied to generate time-frequency distribution image of fault signal. Then, convolutional neural network (CNN) was trained by a lot of time-frequency distribution images generated under different fault conditions. CNN can extract features of the time-frequency distribution image adaptively and select the fault line. The task decomposition framework was first proposed to solve the problem of unbalanced fault signal sample for better feature extraction. A resonant grounding distribution system is simulated to verify this method under different fault conditions and the results showed the detection of the single line-to-ground fault is more accurate.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"22 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91545141","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535607
Tianxin Zhuang, Shujing Yang, M. Ren, B. Song
Partial discharge measurement plays an important role in the assessment of insulation status and fault diagnosis of power equipment. Presently, the most commonly used industrial applications of PD detections are based on the broadband measurement systems that count amplified PD pulses. The limitations of these traditional measurements are that the system requires a relatively high sampling rate and calculation capability, and is very sensitive to the ambient noise. To eliminate noise interference and save the cost of PD detection system, a technique measurement of excess currents, which measures the dielectric response currents through test object before and after PD activities to capture the activities of PD, has been reported in some recent studies. This work aims to explore the parameters that characterize the PD activities via excess current technology and to seek new ideas for PD detection. In this work, a measurement setup for measurement of PD excess currents averaged from 300 periods is applied and three typical insulation defect models were tested under 50Hz voltages. Excess currents for each case are measured. Then the corresponding dielectric loss factors and circuit impedances are obtained by comparing them to the synchronous voltages. The results show that the loss factors increase after PD while the circuit impedances decrease. Meanwhile, the loss factors continue to increase and the circuit impedances continue to decrease as the voltages turn up where the rate of the change shows more rapid in the needle-plate model. Moreover, the loss factors and circuit impedances in the dielectric barrier model and air void model are respectively higher and lower than the values before PD when the voltages drop below the PD extinction voltages, which does not appear in the needle-plate model. These characteristics provide a new idea for PD detection by monitoring the loss factors or circuit impedances via excess current detection.
{"title":"Dielectric Loss Factor and Circuit Impedance Under Partial Discharge Via Excess Current Detection","authors":"Tianxin Zhuang, Shujing Yang, M. Ren, B. Song","doi":"10.1109/CMD.2018.8535607","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535607","url":null,"abstract":"Partial discharge measurement plays an important role in the assessment of insulation status and fault diagnosis of power equipment. Presently, the most commonly used industrial applications of PD detections are based on the broadband measurement systems that count amplified PD pulses. The limitations of these traditional measurements are that the system requires a relatively high sampling rate and calculation capability, and is very sensitive to the ambient noise. To eliminate noise interference and save the cost of PD detection system, a technique measurement of excess currents, which measures the dielectric response currents through test object before and after PD activities to capture the activities of PD, has been reported in some recent studies. This work aims to explore the parameters that characterize the PD activities via excess current technology and to seek new ideas for PD detection. In this work, a measurement setup for measurement of PD excess currents averaged from 300 periods is applied and three typical insulation defect models were tested under 50Hz voltages. Excess currents for each case are measured. Then the corresponding dielectric loss factors and circuit impedances are obtained by comparing them to the synchronous voltages. The results show that the loss factors increase after PD while the circuit impedances decrease. Meanwhile, the loss factors continue to increase and the circuit impedances continue to decrease as the voltages turn up where the rate of the change shows more rapid in the needle-plate model. Moreover, the loss factors and circuit impedances in the dielectric barrier model and air void model are respectively higher and lower than the values before PD when the voltages drop below the PD extinction voltages, which does not appear in the needle-plate model. These characteristics provide a new idea for PD detection by monitoring the loss factors or circuit impedances via excess current detection.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"54 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87018054","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535707
Lei Zhang, Chuan Yu, Le Zhang, Wenfeng Liu, Kangning Wu, Shengtao Li, Jianying Li
Grain size and its spatial distribution are the crucial issues in the study of advanced materials with a grain-grain boundary structure. It not only implies the grain growth mechanism of those materials, but also determines most of their macroscopic properties, such as mechanical strength, current conduction, ageing and so on. Therefore, it is of importance to clarify the grain size distribution (GSD) in ZnO-based varistor ceramics, a key protection element against overvoltage. In the present paper, a new approach based on the log-normal distribution was proposed to analyze the variation of GSD along the thickness direction of two commercial ZnO varistors. It is found that GSD follows log-normal distribution rather than commonly used normal distribution. In addition, with the proposed grain size, i.e., averaged log-normal grain size (dLN) and most probable grain size ($d_{max}$), the variation of GSD along the thickness direction was clearly revealed, which exhibited quite different behavior depending on the samples. With the probability plot, the microscopic uniformity is carefully analyzed and discussed. It is proposed that probability plots can be divided into three regions, representing large grains, grains whose sizes follow the lognormal rule and small grains, respectively. With the proposed method, it is possible to obtain more quantitative information, which is of significance for the further development of ZnO-based varistor ceramics and other advanced materials.
{"title":"A Statistical Approach for Effectively Analyzing the Grain Size Distribution Along the Thickness Direction in Commercial ZnO-Based Varistor Ceramics","authors":"Lei Zhang, Chuan Yu, Le Zhang, Wenfeng Liu, Kangning Wu, Shengtao Li, Jianying Li","doi":"10.1109/CMD.2018.8535707","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535707","url":null,"abstract":"Grain size and its spatial distribution are the crucial issues in the study of advanced materials with a grain-grain boundary structure. It not only implies the grain growth mechanism of those materials, but also determines most of their macroscopic properties, such as mechanical strength, current conduction, ageing and so on. Therefore, it is of importance to clarify the grain size distribution (GSD) in ZnO-based varistor ceramics, a key protection element against overvoltage. In the present paper, a new approach based on the log-normal distribution was proposed to analyze the variation of GSD along the thickness direction of two commercial ZnO varistors. It is found that GSD follows log-normal distribution rather than commonly used normal distribution. In addition, with the proposed grain size, i.e., averaged log-normal grain size (dLN) and most probable grain size ($d_{max}$), the variation of GSD along the thickness direction was clearly revealed, which exhibited quite different behavior depending on the samples. With the probability plot, the microscopic uniformity is carefully analyzed and discussed. It is proposed that probability plots can be divided into three regions, representing large grains, grains whose sizes follow the lognormal rule and small grains, respectively. With the proposed method, it is possible to obtain more quantitative information, which is of significance for the further development of ZnO-based varistor ceramics and other advanced materials.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"29 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91231906","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535674
A. Banik, S. Nielsen, G. Nourbakhsh
The condition assessment of outdoor high voltage insulators is of prime importance to power utilities. There are numerous indicators used for inferring the surface condition of an insulator based on an analysis of measured leakage current. To date, the assumption by most researchers has been that the supply voltage subject on insulators is sinusoidal with little or no harmonic induced distortion. However, in real-life due to ever increasing trend of using power electronics devices in power network, significant amount of harmonic distortion is common and insulators in the power system are directly subjected to this distortion. Therefore, the effectiveness of all those present indices under purely sinusoidal voltage will become questionable in presence of distorted supply voltage. This work aims to investigate the effect of voltage harmonic contents on the measured leakage current of polluted insulators via a developed simulation model. In this paper, by considering the practical supply voltage distortion, authors have shown the major drawback of present indices based condition assessment techniques. Authors have also tried to provide an optimal solution by proposing a Crest Factor (CF) based distinctive index to overcome the problem, based on simulation results.
{"title":"Impact of Voltage Harmonics on Condition Assessment of Polluted Insulator through a Simulation Model","authors":"A. Banik, S. Nielsen, G. Nourbakhsh","doi":"10.1109/CMD.2018.8535674","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535674","url":null,"abstract":"The condition assessment of outdoor high voltage insulators is of prime importance to power utilities. There are numerous indicators used for inferring the surface condition of an insulator based on an analysis of measured leakage current. To date, the assumption by most researchers has been that the supply voltage subject on insulators is sinusoidal with little or no harmonic induced distortion. However, in real-life due to ever increasing trend of using power electronics devices in power network, significant amount of harmonic distortion is common and insulators in the power system are directly subjected to this distortion. Therefore, the effectiveness of all those present indices under purely sinusoidal voltage will become questionable in presence of distorted supply voltage. This work aims to investigate the effect of voltage harmonic contents on the measured leakage current of polluted insulators via a developed simulation model. In this paper, by considering the practical supply voltage distortion, authors have shown the major drawback of present indices based condition assessment techniques. Authors have also tried to provide an optimal solution by proposing a Crest Factor (CF) based distinctive index to overcome the problem, based on simulation results.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"234 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73507684","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535848
Hongmei Wang, Jiangrong Cheng, Dengwei Ding, Weidong Liu, Liang He
the paper proposes a new detection method for partial discharge in transformer. Different from conventional UHF method, which mainly detects electromagnetic wave motivated by discharge, the proposed method detects current pulse signal excited by discharge in UHF band from bushing tap grounding wire. An experiment is performed to study feasibility of the proposed method and to make a contrast with conventional UHF method. It is concluded that, though the sensitivity of proposed method is a little lower compared to internal antenna UHF method, it is still enough to detect partial discharge effectively, and the proposed method is easy to operate and out of problems such as seal which internal UHF method owns. The proposed method offers a relatively practical solution to on-site detection for partial discharge in transformer.
{"title":"A feasibility study on bushing tap UHF sensing method for partial discharge in transformer","authors":"Hongmei Wang, Jiangrong Cheng, Dengwei Ding, Weidong Liu, Liang He","doi":"10.1109/CMD.2018.8535848","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535848","url":null,"abstract":"the paper proposes a new detection method for partial discharge in transformer. Different from conventional UHF method, which mainly detects electromagnetic wave motivated by discharge, the proposed method detects current pulse signal excited by discharge in UHF band from bushing tap grounding wire. An experiment is performed to study feasibility of the proposed method and to make a contrast with conventional UHF method. It is concluded that, though the sensitivity of proposed method is a little lower compared to internal antenna UHF method, it is still enough to detect partial discharge effectively, and the proposed method is easy to operate and out of problems such as seal which internal UHF method owns. The proposed method offers a relatively practical solution to on-site detection for partial discharge in transformer.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"35 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73800344","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535789
K. Thungsook, P. Nimsanong, N. Marukatut, N. Pattanadech
This paper represents the polarization and depolarization current (PDC) measurement of 12/20(24) kV XLPE power cable with different cable lengths, cable dimensions, temperatures and test voltages. In experiment 1, the XLPE cable with 5 m long and cross section of 240 mm2 was prepared for (Case V1) investigation. Moreover, two of 2.5 m cables connected by the pre-molded joint (Case V2) was also prepared. In the experiment 1, the PDC experiment was investigated with different step DC test voltages i.e., 500V, 750V and 1,000V respectively. Besides, the dielectric response of underground cables with the length of 15 cm with cross section of 185 mm2 and the lengths of 2.5 m and 5 m with cross section of 240 mm2 including the length of 100 m with cross section of 70 mm2 were prepared for experiment 2. To investigate the effect of temperatures on dielectric response, the cable specimen with the length of 15 cm with cross section of 185 mm2 was set up under ambient temperatures of 30, 50, 70 and 90 degree Celsius for PDC measurement in experiment 3. PDC test results obtained from the experiments were compared. Then the dielectric parameters for PDC experiment such as charge difference analysis, capacitance ratio analysis, and polarization loss factor were analyzed and reported in this paper.
{"title":"Polarization and Depolarization Current Measurement of Underground Cable with Different Cable lengths, Temperatures and Test Voltages","authors":"K. Thungsook, P. Nimsanong, N. Marukatut, N. Pattanadech","doi":"10.1109/CMD.2018.8535789","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535789","url":null,"abstract":"This paper represents the polarization and depolarization current (PDC) measurement of 12/20(24) kV XLPE power cable with different cable lengths, cable dimensions, temperatures and test voltages. In experiment 1, the XLPE cable with 5 m long and cross section of 240 mm2 was prepared for (Case V1) investigation. Moreover, two of 2.5 m cables connected by the pre-molded joint (Case V2) was also prepared. In the experiment 1, the PDC experiment was investigated with different step DC test voltages i.e., 500V, 750V and 1,000V respectively. Besides, the dielectric response of underground cables with the length of 15 cm with cross section of 185 mm2 and the lengths of 2.5 m and 5 m with cross section of 240 mm2 including the length of 100 m with cross section of 70 mm2 were prepared for experiment 2. To investigate the effect of temperatures on dielectric response, the cable specimen with the length of 15 cm with cross section of 185 mm2 was set up under ambient temperatures of 30, 50, 70 and 90 degree Celsius for PDC measurement in experiment 3. PDC test results obtained from the experiments were compared. Then the dielectric parameters for PDC experiment such as charge difference analysis, capacitance ratio analysis, and polarization loss factor were analyzed and reported in this paper.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"13 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74375798","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535767
Song Wang, Shuang Wang, H. Qiu, Hanke Feng, Shuhong Wang, Ahmed Abu-Siuda
Power transformer is a key equipment in power system. Ensuring the safety operation of transformer is beneficial to decrease the economic loss and casualties. In this paper, twice short-circuit impulse tests are performed on a 10kV transformer. After each test, frequency response analysis (FRA) measurements based on two different terminal connection schemes, namely end to end voltage ratio (EE) and transfer voltage ratio (TF) ways, are conducted to record the FRA results. The impacts of short-circuit on transformer will be investigated by the change of FRA curves. In addition, a numerical index will be utilized to find out the more sensitive measurement connection way to the variation of the traces. The contributions of this paper can give a complement for the current interpretation of the FRA signatures.
{"title":"Frequency Response Analysis of the Transformer Subjected to Twice Short-circuit Impulse Tests Under Two Different Connection Schemes","authors":"Song Wang, Shuang Wang, H. Qiu, Hanke Feng, Shuhong Wang, Ahmed Abu-Siuda","doi":"10.1109/CMD.2018.8535767","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535767","url":null,"abstract":"Power transformer is a key equipment in power system. Ensuring the safety operation of transformer is beneficial to decrease the economic loss and casualties. In this paper, twice short-circuit impulse tests are performed on a 10kV transformer. After each test, frequency response analysis (FRA) measurements based on two different terminal connection schemes, namely end to end voltage ratio (EE) and transfer voltage ratio (TF) ways, are conducted to record the FRA results. The impacts of short-circuit on transformer will be investigated by the change of FRA curves. In addition, a numerical index will be utilized to find out the more sensitive measurement connection way to the variation of the traces. The contributions of this paper can give a complement for the current interpretation of the FRA signatures.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"148 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77363552","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535883
Shuang Wang, Song Wang, Shuhong Wang, H. Qiu, Hanke Feng, Ting Zhu
The safe operation of power transformers is of great significance to the stability of the power system. Radial stability of windings is an important issue for transformer design and maintenance. This paper presents an effective method to analyze the radial stability of windings. The electromagnetic characteristics of a 110 kV two-winding power transformer is calculated and analyzed by finite element method. The mathematical model of radial stability of the power transformer windings under short circuit condition is established. The radial stability analysis of the low winding is performed. The relationship between critical buckling load and its influence factors, including winding material characteristics and winding structure parameters, are obtained based on the buckling analysis. The research results can provide reference for the transformer design, manufacture, operation and maintenance.
{"title":"Research on Radial Stability and Its Influence Factors of Transformer Windings under Short Circuit Fault","authors":"Shuang Wang, Song Wang, Shuhong Wang, H. Qiu, Hanke Feng, Ting Zhu","doi":"10.1109/CMD.2018.8535883","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535883","url":null,"abstract":"The safe operation of power transformers is of great significance to the stability of the power system. Radial stability of windings is an important issue for transformer design and maintenance. This paper presents an effective method to analyze the radial stability of windings. The electromagnetic characteristics of a 110 kV two-winding power transformer is calculated and analyzed by finite element method. The mathematical model of radial stability of the power transformer windings under short circuit condition is established. The radial stability analysis of the low winding is performed. The relationship between critical buckling load and its influence factors, including winding material characteristics and winding structure parameters, are obtained based on the buckling analysis. The research results can provide reference for the transformer design, manufacture, operation and maintenance.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"27 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79156687","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535704
H. Morooka, A. Yamagishi, K. Kawamura, H. Kojima, N. Hayakawa
The surface chemical properties of aged pressboards (PBs) were evaluated to investigate the mechanism behind the increasing tendency of electrostatic charges for diagnosing power transformers. The PBs were taken from several aged transformers, and their surface elemental composition and chemical structures were measured by X-ray photoelectron spectroscopy. The PBs properties were measured after being washed by an organic solvent to remove impregnated mineral oil. Carbon (C) and oxygen (O) atoms were mostly observed on virgin PBs surfaces; these are the atoms that compose cellulose polymer, the main component of kraft pulp. In contrast, sulfur (S) and calcium (Ca) atoms were observed on the surfaces of aged PBs in addition to the C and O atoms. Moreover, the surface densities of the Ca atoms had a good correlation with those of the S atoms. While we detected no S atoms inside the aged PBs, we observed almost the same amount of Ca atoms as in the virgin PBs. Mineral oils mainly consist of hydrocarbons, with very small amounts of components such as sulfur compounds derived from crude oil. Heat stress degrades these sulfur compounds. On the other hand, PBs made of kraft pulp contain a very small amount of metal ions, such as Ca ions. We conclude that S atoms observed on aged PB surfaces are a part of the aged sulfur compounds adsorbed from the mineral oil. The adsorption of aged sulfur compounds induced the migration of Ca ions from the inside of the PBs to the surface, which caused the surface density of the Ca ions to increase. This suggests that the accumulation of Ca ions along with the sulfur compounds led to the increasing tendency of electrostatic charges in aged PBs.
{"title":"Mechanism behind Increasing Electrostatic Charging Tendency in Aged Mineral-Oil-Immersed Pressboards","authors":"H. Morooka, A. Yamagishi, K. Kawamura, H. Kojima, N. Hayakawa","doi":"10.1109/CMD.2018.8535704","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535704","url":null,"abstract":"The surface chemical properties of aged pressboards (PBs) were evaluated to investigate the mechanism behind the increasing tendency of electrostatic charges for diagnosing power transformers. The PBs were taken from several aged transformers, and their surface elemental composition and chemical structures were measured by X-ray photoelectron spectroscopy. The PBs properties were measured after being washed by an organic solvent to remove impregnated mineral oil. Carbon (C) and oxygen (O) atoms were mostly observed on virgin PBs surfaces; these are the atoms that compose cellulose polymer, the main component of kraft pulp. In contrast, sulfur (S) and calcium (Ca) atoms were observed on the surfaces of aged PBs in addition to the C and O atoms. Moreover, the surface densities of the Ca atoms had a good correlation with those of the S atoms. While we detected no S atoms inside the aged PBs, we observed almost the same amount of Ca atoms as in the virgin PBs. Mineral oils mainly consist of hydrocarbons, with very small amounts of components such as sulfur compounds derived from crude oil. Heat stress degrades these sulfur compounds. On the other hand, PBs made of kraft pulp contain a very small amount of metal ions, such as Ca ions. We conclude that S atoms observed on aged PB surfaces are a part of the aged sulfur compounds adsorbed from the mineral oil. The adsorption of aged sulfur compounds induced the migration of Ca ions from the inside of the PBs to the surface, which caused the surface density of the Ca ions to increase. This suggests that the accumulation of Ca ions along with the sulfur compounds led to the increasing tendency of electrostatic charges in aged PBs.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"1 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91225617","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 : 2018-09-01DOI: 10.1109/CMD.2018.8535818
Xiao Li, Yang Xu, Jiangrong Cheng, Weidong Liu, Wensheng Gao
The micro cracks resulted from the defective manufacturing technology are common to see in GIS insulators, and many researches have already been done on it. However, most of these studies are based on the simulative defects made in laboratories, rather than on the defects on real made insulators, and thus the equivalence between the experimental condition and the practical situation in real substations cannot been guaranteed. In this paper, partial discharge (PD) experiments are carried out on a real made GIS post insulator with micro crack inside. It is found that the ultra-high frequency (UHF) method is not sensitive to the PD of this type based on the investigation on the PD characteristics, and the mechanism of the PD process is analyzed to explain why it cannot be detected by the UHF method. According to the special PD characteristics the defect displayed, suggestions on the adjustment of the PD frequency band is made in order to find the micro cracks in GIS insulators on-site.
{"title":"The Characteristics and Detection of the Partial Discharge Induced by the Micro Cracks in GIS Insulators","authors":"Xiao Li, Yang Xu, Jiangrong Cheng, Weidong Liu, Wensheng Gao","doi":"10.1109/CMD.2018.8535818","DOIUrl":"https://doi.org/10.1109/CMD.2018.8535818","url":null,"abstract":"The micro cracks resulted from the defective manufacturing technology are common to see in GIS insulators, and many researches have already been done on it. However, most of these studies are based on the simulative defects made in laboratories, rather than on the defects on real made insulators, and thus the equivalence between the experimental condition and the practical situation in real substations cannot been guaranteed. In this paper, partial discharge (PD) experiments are carried out on a real made GIS post insulator with micro crack inside. It is found that the ultra-high frequency (UHF) method is not sensitive to the PD of this type based on the investigation on the PD characteristics, and the mechanism of the PD process is analyzed to explain why it cannot be detected by the UHF method. According to the special PD characteristics the defect displayed, suggestions on the adjustment of the PD frequency band is made in order to find the micro cracks in GIS insulators on-site.","PeriodicalId":6529,"journal":{"name":"2018 Condition Monitoring and Diagnosis (CMD)","volume":"58 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78406554","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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