Pub Date : 2019-06-01DOI: 10.1109/EIC43217.2019.9046608
Hasti Haghighi, I. Cotton
This paper describes the results derived from thermogravimetric analysis (TGA) work on poly (4,4‘-oxydiphenylene-pyromellitimide), or more commonly known as Kapton film. The test are completed under heating rates of 5, 10, 20, and 50 K/min and two distinct atmospheres, concentrations of 21 % and 3 % oxygen. The atmospheres chosen mimic the oxygen concentrations at ground-level and at a cruising altitude of 15 km, which are the two extremes of the environments the insulation is expected to operate in when being applied in commercial aircraft electrical systems. From the rate of TGA conversion data at various temperatures, kinetic parameters such as the activation energy (Ea) and pre-exponential factor (A) are found. This is then used to illustrate the relationship that can exist between oxygen concentrations and the ageing and degradation rates of polyimide insulation as expressed using the Arrhenius equation. From this, differences between the ageing mechanisms and relative lifetimes of insulation systems in an aerospace application compared to those operating in ground-based systems can be found.
{"title":"Analysis of the Degradation Kinetics of Kapton Film in an Aerospace Environment","authors":"Hasti Haghighi, I. Cotton","doi":"10.1109/EIC43217.2019.9046608","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046608","url":null,"abstract":"This paper describes the results derived from thermogravimetric analysis (TGA) work on poly (4,4‘-oxydiphenylene-pyromellitimide), or more commonly known as Kapton film. The test are completed under heating rates of 5, 10, 20, and 50 K/min and two distinct atmospheres, concentrations of 21 % and 3 % oxygen. The atmospheres chosen mimic the oxygen concentrations at ground-level and at a cruising altitude of 15 km, which are the two extremes of the environments the insulation is expected to operate in when being applied in commercial aircraft electrical systems. From the rate of TGA conversion data at various temperatures, kinetic parameters such as the activation energy (Ea) and pre-exponential factor (A) are found. This is then used to illustrate the relationship that can exist between oxygen concentrations and the ageing and degradation rates of polyimide insulation as expressed using the Arrhenius equation. From this, differences between the ageing mechanisms and relative lifetimes of insulation systems in an aerospace application compared to those operating in ground-based systems can be found.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134167691","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046565
Feipeng Wang, Muhammad Zeeshan Khan, Li He, Zhengyong Huang, Moon-Jae Yang
In this work, nano-alumina / epoxy resin nanocomposites with nano-alumina fraction of 1, 3 and 5 wt.% were prepared and subsequently fluorinated at 40°C in F2/N2 gas mixture (20/80 v/v) with pressure of 0.05 MPa. The nano-alumina was treated by the saline coupling agent of $gamma$-aminopropyltriethoxysilane (KH550) to restrict the aggregation. The chemical bonding was examined by Fourier transform infrared spectroscopy (FTIR) which has indicated the molecular-chain scission during the gas-phase fluorination. The trap density and trap level distribution in the nanocomposites before and after fluorination were investigated by thermally stimulated current (TSC). The results shown that fluorination introduces shallow traps on the surface which increases the surface conductivity. Hence depth of charge traps are considerably reduced after fluorination. The results shown that nanocomposites with 1 wt.% nano-alumina appeared with deeper traps and higher trap energy level comparing with the other samples. However with increased nano-alumina mass fraction, e.g. 3 and 5 wt.%, considerable over-lapping interaction zones appear, that results in the reduced trap energy level.
{"title":"Effect of Gas-phase Fluorination on Trap Level of Nano-Alumina / Epoxy Resin Nanocomposites","authors":"Feipeng Wang, Muhammad Zeeshan Khan, Li He, Zhengyong Huang, Moon-Jae Yang","doi":"10.1109/EIC43217.2019.9046565","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046565","url":null,"abstract":"In this work, nano-alumina / epoxy resin nanocomposites with nano-alumina fraction of 1, 3 and 5 wt.% were prepared and subsequently fluorinated at 40°C in F2/N2 gas mixture (20/80 v/v) with pressure of 0.05 MPa. The nano-alumina was treated by the saline coupling agent of $gamma$-aminopropyltriethoxysilane (KH550) to restrict the aggregation. The chemical bonding was examined by Fourier transform infrared spectroscopy (FTIR) which has indicated the molecular-chain scission during the gas-phase fluorination. The trap density and trap level distribution in the nanocomposites before and after fluorination were investigated by thermally stimulated current (TSC). The results shown that fluorination introduces shallow traps on the surface which increases the surface conductivity. Hence depth of charge traps are considerably reduced after fluorination. The results shown that nanocomposites with 1 wt.% nano-alumina appeared with deeper traps and higher trap energy level comparing with the other samples. However with increased nano-alumina mass fraction, e.g. 3 and 5 wt.%, considerable over-lapping interaction zones appear, that results in the reduced trap energy level.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133085754","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046597
T. Hammarström
Speed drives fed by pulse width modulated (PWM) inverters allows a more efficient use of electric energy. The drawback is however that the stress imposed on motor winding insulation increases due to a higher frequency harmonic content compared to the classical 50 Hz sinusoidal voltages. High frequency contributions have been observed in high voltage DC (HVDC) applications as well. In particular, partial discharges (PDs) considered the major contributor to the reduction in the insulation life time. It has been shown that the usage of electrical filters decreases electrical stress imposed on the insulation. Another option is to use multi level inverters, which have been shown to reduce magnitude of the PDs. It however remains to explain how the size of these voltage steps as well as polarity influences the level of PDs. Here twisted pair test objects are exposed to PWM inverter waveform at various rise times. Both bipolar and unipolar waveforms as well as different step sizes and rise times of each voltage flank are employed to present a gradual change between bipolar PWM to a more constant DC voltage magnitude with superimposed voltage ripple. To compare the performances, measurements of both PD inception and extinction voltages were conducted for the different cases. Additionally, the total number of PDs, their average maximum amplitude per cycle and pulse repetitive PD pattern (PRPD) are presented. The decreased step size to resemble more HVDC waveform and the resulting change in PD characteristics is discussed. Important factors are the time until PDs are observed (time lag) together with observed polarity dependences.
{"title":"The Implications on the PD Characteristics of Unipolar versus Bipolar PWM waveforms","authors":"T. Hammarström","doi":"10.1109/EIC43217.2019.9046597","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046597","url":null,"abstract":"Speed drives fed by pulse width modulated (PWM) inverters allows a more efficient use of electric energy. The drawback is however that the stress imposed on motor winding insulation increases due to a higher frequency harmonic content compared to the classical 50 Hz sinusoidal voltages. High frequency contributions have been observed in high voltage DC (HVDC) applications as well. In particular, partial discharges (PDs) considered the major contributor to the reduction in the insulation life time. It has been shown that the usage of electrical filters decreases electrical stress imposed on the insulation. Another option is to use multi level inverters, which have been shown to reduce magnitude of the PDs. It however remains to explain how the size of these voltage steps as well as polarity influences the level of PDs. Here twisted pair test objects are exposed to PWM inverter waveform at various rise times. Both bipolar and unipolar waveforms as well as different step sizes and rise times of each voltage flank are employed to present a gradual change between bipolar PWM to a more constant DC voltage magnitude with superimposed voltage ripple. To compare the performances, measurements of both PD inception and extinction voltages were conducted for the different cases. Additionally, the total number of PDs, their average maximum amplitude per cycle and pulse repetitive PD pattern (PRPD) are presented. The decreased step size to resemble more HVDC waveform and the resulting change in PD characteristics is discussed. Important factors are the time until PDs are observed (time lag) together with observed polarity dependences.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131100568","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046564
Yuwei Wang, Qizheng Ye, Ziqing Guo
In this study, a method was developed for diagnosing the non-thermal equilibrium physical properties of a free burning arc in air using the chromaticity information from a visible image. After extracting RGB values from the image and using digital image processing, the following two comparisons are made: (1) the red-component rate of arc for different electrode materials; (2) the chromaticity distribution at different stages of the AC arc; Analyses are also conducted based on the space radiation characteristics of the arc, differences due to the electrode material. Experiments showed that the proposed method can distinguish experimental materials and arc stages. Furthermore, since the image method is used, the method does not need to assume that the arc is in the thermal equilibrium stage.
{"title":"Research on arc non-thermal equilibrium characteristics using chromaticity information from a visible digital image","authors":"Yuwei Wang, Qizheng Ye, Ziqing Guo","doi":"10.1109/EIC43217.2019.9046564","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046564","url":null,"abstract":"In this study, a method was developed for diagnosing the non-thermal equilibrium physical properties of a free burning arc in air using the chromaticity information from a visible image. After extracting RGB values from the image and using digital image processing, the following two comparisons are made: (1) the red-component rate of arc for different electrode materials; (2) the chromaticity distribution at different stages of the AC arc; Analyses are also conducted based on the space radiation characteristics of the arc, differences due to the electrode material. Experiments showed that the proposed method can distinguish experimental materials and arc stages. Furthermore, since the image method is used, the method does not need to assume that the arc is in the thermal equilibrium stage.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125998068","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046554
M. Partyka, G. Bridges, B. McDermid, T. Black, B. Kordi
Compared with other methods, there is limited research on the measurement of partial discharges (PD) in rotating machine windings using antenna-based UHF techniques. In this work, to investigate the value of measuring winding PD at higher frequencies, we designed and fabricated three patch antennas operating at 900, 1500, and 2450 MHz. The antennas are used to perform UHF PD measurements on single rotating machine bars rated at 13.8 kV. Measurements were performed in a laboratory with the specimens placed in grounded dummy stator slots. PD was produced by over-stressing the test specimens with a PD-free high voltage test set, and also by shorting out stress control region(s) using semi-conductive tape. The UHF PRPD patterns were compared to those from measurements on the same specimen with a VHF commercial instrument. It was clearly shown that PD can be measured with UHF patch antennas, despite some disagreement between UHF and VHF PRPD patterns.
{"title":"UHF Measurement of Partial Discharge on Stator Bars Using Patch Antennas","authors":"M. Partyka, G. Bridges, B. McDermid, T. Black, B. Kordi","doi":"10.1109/EIC43217.2019.9046554","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046554","url":null,"abstract":"Compared with other methods, there is limited research on the measurement of partial discharges (PD) in rotating machine windings using antenna-based UHF techniques. In this work, to investigate the value of measuring winding PD at higher frequencies, we designed and fabricated three patch antennas operating at 900, 1500, and 2450 MHz. The antennas are used to perform UHF PD measurements on single rotating machine bars rated at 13.8 kV. Measurements were performed in a laboratory with the specimens placed in grounded dummy stator slots. PD was produced by over-stressing the test specimens with a PD-free high voltage test set, and also by shorting out stress control region(s) using semi-conductive tape. The UHF PRPD patterns were compared to those from measurements on the same specimen with a VHF commercial instrument. It was clearly shown that PD can be measured with UHF patch antennas, despite some disagreement between UHF and VHF PRPD patterns.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130755442","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046619
S. Morsalin, A. Sahoo, B. Phung
Polymeric insulation, especially cross-linked polyethylene (XLPE) insulated power cables are widely used in practice to transport electrical energy. XLPE has excellent dielectric properties, but its degradation due to various factors while in service is unlikely to avoid. Moreover, electrical, mechanical or thermal stresses accelerate the ageing process and shorten the lifespan. In the era of smart grid, its safe and reliable operation is vital. Hence, condition monitoring of insulation through diagnostic testing has become critically important to the smart maintenance of electrical infrastructure. In this paper, the diagnostic behaviors of XLPE insulation are explained by using two popular diagnostic methods, partial discharge (PD) and dielectric response (DR) measurements. For PD diagnosis, a comparative study of surface discharge and their characteristics under conventional power frequency (50 Hz) and very low frequency (0.1 Hz) excitation are presented. Dielectric responses are investigated in the frequency domain by $mathrm{tan}delta$ measurement and in the time domain by pol/depolarization current measurement. It is shown that useful information for insulation diagnosis can be extracted from the measurement results.
{"title":"Diagnostic Testing of Power Cable Insulation For Reliable Smart Grid Operation","authors":"S. Morsalin, A. Sahoo, B. Phung","doi":"10.1109/EIC43217.2019.9046619","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046619","url":null,"abstract":"Polymeric insulation, especially cross-linked polyethylene (XLPE) insulated power cables are widely used in practice to transport electrical energy. XLPE has excellent dielectric properties, but its degradation due to various factors while in service is unlikely to avoid. Moreover, electrical, mechanical or thermal stresses accelerate the ageing process and shorten the lifespan. In the era of smart grid, its safe and reliable operation is vital. Hence, condition monitoring of insulation through diagnostic testing has become critically important to the smart maintenance of electrical infrastructure. In this paper, the diagnostic behaviors of XLPE insulation are explained by using two popular diagnostic methods, partial discharge (PD) and dielectric response (DR) measurements. For PD diagnosis, a comparative study of surface discharge and their characteristics under conventional power frequency (50 Hz) and very low frequency (0.1 Hz) excitation are presented. Dielectric responses are investigated in the frequency domain by $mathrm{tan}delta$ measurement and in the time domain by pol/depolarization current measurement. It is shown that useful information for insulation diagnosis can be extracted from the measurement results.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114069480","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046522
C. Staubach, S. Meissner, A. Cimino
In this paper test bars are mechanically aged by means of a cyclic bending test setup. At specific time intervals the dielectric response analysis is performed on these bars. This diagnostic technique consists of a combination of polarization and depolarization current (PDC) measurement in the time-domain and frequency-domain processing of the measurement results together with a frequency-domain spectroscopy (FDS). The aim of this work is to investigate the possibility to assess the degree of mechanical deterioration by means of this diagnostic technique. Ideally, a correlation between the mechanical lifetime consumption and the change in the measurement results can be derived.
{"title":"Dielectric response analysis as tool to assess the mechanical deterioration of VPI insulation","authors":"C. Staubach, S. Meissner, A. Cimino","doi":"10.1109/EIC43217.2019.9046522","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046522","url":null,"abstract":"In this paper test bars are mechanically aged by means of a cyclic bending test setup. At specific time intervals the dielectric response analysis is performed on these bars. This diagnostic technique consists of a combination of polarization and depolarization current (PDC) measurement in the time-domain and frequency-domain processing of the measurement results together with a frequency-domain spectroscopy (FDS). The aim of this work is to investigate the possibility to assess the degree of mechanical deterioration by means of this diagnostic technique. Ideally, a correlation between the mechanical lifetime consumption and the change in the measurement results can be derived.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116536873","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046615
Benard M. Makaa, G. Irungu, D. Murage
Mineral insulation oils have been used as a liquid insulation in electrical equipment for several decades. However, mineral oil is non-biodegradable and non-renewable. It has been predicted that they may run out in the near future. There is thus an urgent need to find their alternatives. Natural, plant based insulating oils are the solution. They are non-toxic, and possess higher fire points and excellent biodegradability characteristics. Therefore, to improve fire safety of transformers and to decrease the harmful environmental impact, there is an increasing demand for these insulating liquids as transformer insulating oils. Persea americana ester (PAE), a plant based oil has high biodegradability and is renewable. PAE has shown through experiments, a likelihood of being an alternative to mineral insulation oil (MIO) because of its good physico-chemical and electrical properties, so far investigated. Since insulating oil for transformers is used over several years, it is imperative to study the ageing characteristics of proposed new insulation oils. Accelerated ageing using open beaker method with copper catalyst was carried out to predict the reliability of Persea americana oil when in operation. The ageing test was based on accelerated thermal ageing to induce the ageing mechanisms within a short period (96 and 164 hours). Results obtained for Specific Resistivity at 27°C and 90°C, Dielectric dissipation factor, Total acidity and sludge for PAE; suggest that PAE could be a potential transformer insulating liquid. For comparison, the corresponding properties of mineral insulation oil (MIO) in the same experimental conditions were also measured. The results obtained as per the IEC and ASTM specifications gives hope for new natural liquid insulation oil.
{"title":"Study on the Ageing Characteristics of Persea Americana Oil as an Alternative Transformer Insulation oil","authors":"Benard M. Makaa, G. Irungu, D. Murage","doi":"10.1109/EIC43217.2019.9046615","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046615","url":null,"abstract":"Mineral insulation oils have been used as a liquid insulation in electrical equipment for several decades. However, mineral oil is non-biodegradable and non-renewable. It has been predicted that they may run out in the near future. There is thus an urgent need to find their alternatives. Natural, plant based insulating oils are the solution. They are non-toxic, and possess higher fire points and excellent biodegradability characteristics. Therefore, to improve fire safety of transformers and to decrease the harmful environmental impact, there is an increasing demand for these insulating liquids as transformer insulating oils. Persea americana ester (PAE), a plant based oil has high biodegradability and is renewable. PAE has shown through experiments, a likelihood of being an alternative to mineral insulation oil (MIO) because of its good physico-chemical and electrical properties, so far investigated. Since insulating oil for transformers is used over several years, it is imperative to study the ageing characteristics of proposed new insulation oils. Accelerated ageing using open beaker method with copper catalyst was carried out to predict the reliability of Persea americana oil when in operation. The ageing test was based on accelerated thermal ageing to induce the ageing mechanisms within a short period (96 and 164 hours). Results obtained for Specific Resistivity at 27°C and 90°C, Dielectric dissipation factor, Total acidity and sludge for PAE; suggest that PAE could be a potential transformer insulating liquid. For comparison, the corresponding properties of mineral insulation oil (MIO) in the same experimental conditions were also measured. The results obtained as per the IEC and ASTM specifications gives hope for new natural liquid insulation oil.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"248 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114551641","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046591
Tianxin Zhuang, Xuze Gao, M. Ren, Siyun Wang, Junkai Huang
Insulation of power electronic devices and converter station equipment is often under superimposed AC-DC voltage. The understanding of PD characteristics under AC-DC combined excitation plays an important role in designing the insulation of power electronic device. Previous researches focused on the stochastic features and mechanism under AC or DC voltages, while little attention was paid to the PD-induced charge movements under superimposed AC-DC field. The charge movements include the transient behavior of PD and the slow movement, which can be characterized by the transient PD current and the excess current respectively. In this paper, a composite AC-DC voltage is applied to a pair of rod-plane electrodes sandwiching epoxy film. And a sensitive high-frequency Rogowski coil and a capacitor-resistor shunt impedance are used to simultaneously measure the transient PD current and the excess current during PD. The excess current can be measured by cancelling the capacitive current from the total current. In the measurement, first set the AC voltage at 1.5 times the AC PDIV, then gradually raise the DC voltage up. The results show that, as the DC bias increases, the phase distributions of PD events are expanded, but the average PD currents and excess currents are lower than that under the pure AC electric field. Moreover, only few PD events are observed when the DC voltage rises close to the peak of AC voltage, and the surface flashover starts once the DC voltage rises above the peak of AC voltage. It is proved that the additional DC voltage suppress the corona discharge excited by the AC voltage to a certain extent, but it may also result in surface flashover if the DC bias exceeds the AC amplitude.
{"title":"Characteristics of the Partial Discharge-induced Current along Epoxy resin film under Superimposed AC- DC Voltage","authors":"Tianxin Zhuang, Xuze Gao, M. Ren, Siyun Wang, Junkai Huang","doi":"10.1109/EIC43217.2019.9046591","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046591","url":null,"abstract":"Insulation of power electronic devices and converter station equipment is often under superimposed AC-DC voltage. The understanding of PD characteristics under AC-DC combined excitation plays an important role in designing the insulation of power electronic device. Previous researches focused on the stochastic features and mechanism under AC or DC voltages, while little attention was paid to the PD-induced charge movements under superimposed AC-DC field. The charge movements include the transient behavior of PD and the slow movement, which can be characterized by the transient PD current and the excess current respectively. In this paper, a composite AC-DC voltage is applied to a pair of rod-plane electrodes sandwiching epoxy film. And a sensitive high-frequency Rogowski coil and a capacitor-resistor shunt impedance are used to simultaneously measure the transient PD current and the excess current during PD. The excess current can be measured by cancelling the capacitive current from the total current. In the measurement, first set the AC voltage at 1.5 times the AC PDIV, then gradually raise the DC voltage up. The results show that, as the DC bias increases, the phase distributions of PD events are expanded, but the average PD currents and excess currents are lower than that under the pure AC electric field. Moreover, only few PD events are observed when the DC voltage rises close to the peak of AC voltage, and the surface flashover starts once the DC voltage rises above the peak of AC voltage. It is proved that the additional DC voltage suppress the corona discharge excited by the AC voltage to a certain extent, but it may also result in surface flashover if the DC bias exceeds the AC amplitude.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115434016","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 : 2019-06-01DOI: 10.1109/EIC43217.2019.9046515
V. Grau, R. D. De Doncker
Next generation silicon carbide (SiC) and gallium nitride (GaN) semiconductors offer much faster switching characteristics in power electronic devices. The faster switching speed allows higher switching frequencies in combination with lower losses, which leads to smaller components and thus, a higher power density. However, the high voltage slopes associated with fast switching cause exceeding stress on the insulation systems, especially of coil windings. This increased stress results in accelerated aging and thus, premature failure of the insulation system. This paper focuses on the design and execution of experiments to quantify the detrimental effects of fast switching on the insulation system of coil windings. To investigate these effects, a dv/dt- generator is developed to excite various specimens with steep voltage slopes. Commercial products are not suitable for this purpose as they are either not available on the market or do not fully exploit the potential of the next generation semiconductors. A SiC-based inverter with an H-bridge topology is selected. The dielectric strength of twisted pair enameled wires are tested using a standardized insulation tester and the proposed dv/dt-generator. While the specimen withstands the standardized insulation test, partial discharges occur during excitation with high dv/dt, which leads to a premature breakdown after short time, even though the dv/dt test voltage is less than a sixth of the standardized test. It is experimentally observed that the steepness of the voltage slope has a major impact on the insulation system.
{"title":"The Effects of Steep Voltage Slopes on Insulation Systems of Coil Windings caused by Next Generation Power Semiconductor Devices","authors":"V. Grau, R. D. De Doncker","doi":"10.1109/EIC43217.2019.9046515","DOIUrl":"https://doi.org/10.1109/EIC43217.2019.9046515","url":null,"abstract":"Next generation silicon carbide (SiC) and gallium nitride (GaN) semiconductors offer much faster switching characteristics in power electronic devices. The faster switching speed allows higher switching frequencies in combination with lower losses, which leads to smaller components and thus, a higher power density. However, the high voltage slopes associated with fast switching cause exceeding stress on the insulation systems, especially of coil windings. This increased stress results in accelerated aging and thus, premature failure of the insulation system. This paper focuses on the design and execution of experiments to quantify the detrimental effects of fast switching on the insulation system of coil windings. To investigate these effects, a dv/dt- generator is developed to excite various specimens with steep voltage slopes. Commercial products are not suitable for this purpose as they are either not available on the market or do not fully exploit the potential of the next generation semiconductors. A SiC-based inverter with an H-bridge topology is selected. The dielectric strength of twisted pair enameled wires are tested using a standardized insulation tester and the proposed dv/dt-generator. While the specimen withstands the standardized insulation test, partial discharges occur during excitation with high dv/dt, which leads to a premature breakdown after short time, even though the dv/dt test voltage is less than a sixth of the standardized test. It is experimentally observed that the steepness of the voltage slope has a major impact on the insulation system.","PeriodicalId":340602,"journal":{"name":"2019 IEEE Electrical Insulation Conference (EIC)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124739757","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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