12 results on '"Gao, Chunjia"'
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2. The influence of surface charge accumulation on flashover voltage of GIS/GIL basin insulator under various voltage stresses
- Author
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Qi, Bo, Gao, Chunjia, Li, Chengrong, and Xiong, Jun
- Published
- 2019
- Full Text
- View/download PDF
3. The flashover of epoxy initiated by micron metal particles under DC voltage: phenomenon and mechanism.
- Author
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Qi, Bo, Yang, Zhuodong, Yang, Xiao, Huang, Meng, Gao, Chunjia, Zhang, Yi, Luo, Yuan, Lu, Licheng, and Li, Chengrong
- Subjects
HIGH-voltage direct current transmission ,FLASHOVER ,VAN der Waals forces - Abstract
Epoxy post-insulator is one of the key parts in SF
6 gas-insulated DC wall bushing, which is irreplaceable in high voltage direct current transmission projects. Flashovers occur on post-insulators frequently, where a great number of tiny metal particles exist. The micron metal particles attached to the epoxy will change the insulation state of the surface. However, this relation between microstructure of material and macroscopic electrical properties on flashover would still arouse controversy. In order to study the effect of particles on the flashover characteristics, the particles generated from wear of spring in DC wall bushing were selected, the surface potential decay along surface and the DC flashover voltage of epoxy attached with particles were measured. The results show that the discrete particles could increase surface trap level by 0.025 eV under the effect of Van der Waals force. Furthermore, the deeper traps could capture the charge during the streamer development and inhibit the flashover, when the particle amount less than 500 per mm2 . If the particles are more enough to form the continuous paths, these conductive paths could promote the streamer to propagate, which shortens the insulation distance, increases the electric field, and decreases the flashover voltage by 50% finally. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
4. The flashover of epoxy initiated by micron metal particles under DC voltage: phenomenon and mechanism.
- Author
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Qi, Bo, Yang, Zhuodong, Yang, Xiao, Huang, Meng, Gao, Chunjia, Zhang, Yi, Luo, Yuan, Lu, Licheng, and Li, Chengrong
- Subjects
HIGH-voltage direct current transmission ,FLASHOVER ,VAN der Waals forces - Abstract
Epoxy post-insulator is one of the key parts in SF
6 gas-insulated DC wall bushing, which is irreplaceable in high voltage direct current transmission projects. Flashovers occur on post-insulators frequently, where a great number of tiny metal particles exist. The micron metal particles attached to the epoxy will change the insulation state of the surface. However, this relation between microstructure of material and macroscopic electrical properties on flashover would still arouse controversy. In order to study the effect of particles on the flashover characteristics, the particles generated from wear of spring in DC wall bushing were selected, the surface potential decay along surface and the DC flashover voltage of epoxy attached with particles were measured. The results show that the discrete particles could increase surface trap level by 0.025 eV under the effect of Van der Waals force. Furthermore, the deeper traps could capture the charge during the streamer development and inhibit the flashover, when the particle amount less than 500 per mm2 . If the particles are more enough to form the continuous paths, these conductive paths could promote the streamer to propagate, which shortens the insulation distance, increases the electric field, and decreases the flashover voltage by 50% finally. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
5. Insulation degradation affected by micron metal particles attached on epoxy surface: charge accumulation and flashover voltage.
- Author
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Yang, Zhuodong, Qi, Bo, Yang, Xiao, Gao, Chunjia, Zhang, Yi, Luo, Yuan, Sun, Caixin, and Li, Chengrong
- Subjects
SURFACE charging ,VOLTAGE ,EPOXY resins ,HIGH voltages ,METALS ,FLASHOVER ,SURFACE charges - Abstract
The micron metal particles are inevitably produced in long-term operation condition of high voltage direct current SF
6 insulated apparatus, which could frequently cause the surface discharge. Degradation of long-term surface discharge will be a severe threat to the insulation strength. Aiming at this problem, the surface charge accumulation and flashover voltage of epoxy itself before and after discharge degradation by particles were compared in this paper. The composition after degradation was measured by EDS and FTIR. The microstructure was observed by SEM. The roughness was measured as well. The trap distribution was measured by SPD. The mechanism of degradation and its effect on insulation characteristics were analyzed. The results show that the surface charge accumulation increase three times after degradation. Additionally, flashover voltage decreases 19% after degradation. The smoothly surface after degradation decrease the trap energy level for 14%, which might be the change reason of surface charge accumulation and flashover voltage. This paper can offer as a reference for the effect of micron metal particles on insulation degradation in SF6 gas insulated equipment. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
6. Effect of Different DC Prestressed Time on Flashover Characteristics of Epoxy Resin Under Polarity Reversal Voltage.
- Author
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Qi, Bo, Yang, Zhuodong, Yang, Xiao, Gao, Chunjia, Lu, Licheng, Zhang, Yi, Li, Li, Sun, Caixin, and Li, Chengrong
- Subjects
ELECTRIC charge ,ELECTRIC field strength ,FLASHOVER ,EPOXY resins ,BUSHINGS ,SURFACE charges ,CHARGE measurement ,VOLTAGE - Abstract
DC wall bushing is one of the key equipment in high-voltage direct current (HVDC) transmission project. At present, post insulators based on epoxy composites are widely used for supporting insulation in SF6-insulated apparatus. However, the flashover faults caused by surface charge accumulation can be a severe threat to the long-term operation of the post insulators under dc field. Therefore, the issue of charge accumulation on epoxy post insulators in HVDC wall bushing and its effect on flashover has been widely concerned. Aiming at this problem, the flashover characteristics of epoxy samples in SF6 gas under polarity reversal conditions with dc voltage prestressed for 10–600 min were measured in this article. The flashover process is analyzed through surface charge distribution measurement and electric field computation. The results show that with the increase of prestressed time, the accumulated negative charge density could reach $-14.8\,\,\mu \text{C}/\text{m}^{{2}}$ , which led to a 12% increase in maximum field strength. As a result, the polarity reversal flashover voltage could decrease by 12% and the flashover time delay could decrease by 84.6%. This article can offer as a reference for the effect of surface charge accumulation on flashover in SF6 gas-insulated equipment. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. Effect of DC electric field on moisture migration characteristics in oil‐pressboard.
- Author
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Yuan, Qing, Qi, Bo, Zhao, Jianshe, Gao, Chunjia, Yang, Xiao, Zhang, Shuqi, and Li, Chengrong
- Published
- 2021
- Full Text
- View/download PDF
8. Influence of moisture on the interface charge of oil–pressboard composite insulation under DC voltage
- Author
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Yanqiu Jiao, Xiaolin Zhao, Li Chengrong, Zhang Shuqi, Gao Chunjia, and Qi Bo
- Subjects
Materials science ,surface charge accumulation ,Transformer oil ,composite insulating materials ,surface charge density ,020209 energy ,power transformer insulation ,lcsh:QC501-721 ,Energy Engineering and Power Technology ,02 engineering and technology ,interfacial charge density ,01 natural sciences ,oil-pressboard composite insulation ,oil resistivity ,law.invention ,Kerr electro-optic effect ,negative charges ,law ,Electric field ,0103 physical sciences ,lcsh:Electricity ,0202 electrical engineering, electronic engineering, information engineering ,interface charge ,Surface charge ,pressboard resistivity ,Electrical and Electronic Engineering ,Composite material ,Transformer ,moisture content ,010302 applied physics ,Pressboard ,transformer oil ,Moisture ,Charge density ,electric field strengths ,surface charging ,Maxwell-Wagner theory ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,DC voltage ,lcsh:TK1-9971 ,Voltage - Abstract
The distortion of the electric field in the oil–pressboard composite insulation caused by the accumulation of the interface charge is detrimental to both the insulation design and operation of converter transformers. The influence of moisture content on the surface charge accumulation of oil–pressboard insulation under DC voltage was studied in this study. In accordance with the Kerr electro-optic effect, the electric field strengths in transformer oil and the surface charge density were acquired after applying the positive and negative DC voltages in three oil–pressboard insulation models with different moisture content, respectively. The resistivities of the oil and pressboard in three models, namely Model 1# with 3.8–4.2 ppm moisture in oil and 0.35–0.37% moisture in pressboard, Model 2# with 7.6–7.9 ppm moisture in oil and 0.79–0.82% moisture in pressboard and Model 3# with 14.9–15.4 ppm moisture in oil and 1.39–1.42% moisture in pressboard, was also measured. The results indicate that: (i) as negative charges in oil accumulated on the pressboard surface in a much greater speed than the positive ones, the electric field in transformer oil under negative DC voltage decreases more rapidly with time than that under positive DC voltage; (ii) the increase of the moisture content in both oil and pressboard, under either positive or negative DC voltage, leads to the decrease of both the electric field strength in transformer oil and the charge density with time; and (iii) the increase of moisture content could not only decrease the resistivity of both oil and pressboard, but also the ratio of the resistivity between the pressboard and the oil. On the basis of the Maxwell–Wagner theory, the decrease of the ratio between the pressboard and oil could lead to the decrease of the interfacial charge density, leading to the slow transient process of the electric field in transformer oil under DC voltage.
- Published
- 2018
9. Key dielectric properties and performance evaluation of high-density pressboard for electrical purposes.
- Author
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Gao, Chunjia, Qi, Bo, Li, Chengrong, Lu, Licheng, and Zhang, Shuqi
- Subjects
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DIELECTRIC properties , *CARDBOARD , *PERMITTIVITY , *PERMITTIVITY measurement , *INSULATING materials , *PERFORMANCE evaluation - Abstract
A high-density electrical pressboard plays a significant role in maintaining the safe and stable operation of power equipment. In response to concerns about finding an evaluation method based on the dielectric performance of the pressboard, this study set up a measurement platform to capture data for three key dielectric properties, namely, relative permittivity, volume resistivity, and surface resistivity. Five kinds of pressboards obtained from representative insulating materials manufacturers were chosen as test samples, and the effects of temperature and moisture content of the pressboards on their dielectric properties were quantitatively investigated. The results indicated that (1) with increasing temperature and moisture content of the pressboards, there was an increase in the relative permittivity, with a maximum increase of 55.85%; (2) the higher the temperature and moisture content of the pressboards, the lower the volume and surface resistivity, and the maximum reduction was as much as 98.25%; (3) significant differences exist in the dielectric properties of different batches of pressboards from the same manufacturer; and (4) the results of tests of conventional physical and chemical properties of pressboards could help explain the differences in dielectric properties between different types of pressboards. Finally, based on the variation in dielectric properties for different test conditions, a method for evaluating the performance of pressboards is proposed. Using this method, the dielectric properties of different insulating pressboard products can be compared horizontally, which will provide data support and technical reference for the design of insulation structures and the selection of insulating materials for different applications. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
10. Kerr Electro-Optic Sensor for Electric Field in Large-Scale Oil–Pressboard Insulation Structure.
- Author
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Gao, Chunjia, Qi, Bo, Gao, Yuan, Zhu, Zongwang, and Li, Chengrong
- Subjects
- *
ELECTRIC fields , *KERR electro-optical effect , *ELECTRIC field strength , *OPTICAL elements , *POWER transformers - Abstract
The design of the oil–pressboard/paper insulation structure is the key to maintain the safe and reliable operation of power transformers, which mainly relies on simulation and verification test undertaken with simple or equivalent models, falling short of the physical entity verification undertaken in the large-scale structure. Based on the Kerr electro-optic effect and the optical fiber technology, a novel electric field measuring sensor was developed in this paper for the application test in the large-scale oil–pressboard structure. The sensor is contained of collimator, total reflection prism, coupler, and customized optical elements, whose appearance is a miniature capsule-shaped configuration. The key technical performance parameters of sensor were obtained, for instance, and the effect of imported sensor on the electric field under measurement is an average 1.17% reduction in intensity; the sensitivity of designed system is 162.84 V/mm under ac voltage and 40.43 V/mm under dc voltage. Under dc voltage, the measuring accuracy of the designed system is greater than 97.42%, while in the context of ac voltage, it could reach 97.14%. The application test was conducted to capture the dynamic process of the electric field in oil in the large-scale outlet device model, which has three uniformly spaced oil spacings divided by pressboards, under ac voltage, dc voltage, and polarity reversal voltage. The experimental results verify that the developed electric field sensor could be effectively and reliably applied in the large-scale oil–pressboard insulation, and it could be confidently inferred that the larger the scale of insulation structure, the better is the performance of sensor. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
11. Surface charge distribution on GIS insulator under DC/AC voltage.
- Author
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Qi, Bo, Gao, Chunjia, ShunLiu, Zhao, Linjie, and Li, Chengrong
- Subjects
- *
GAS insulation in electric switchgears , *ELECTRIC switchgear insulation , *ELECTRICAL insulation gases , *SURFACE charges , *SURFACE charging - Abstract
The Gas Insulated Switchgear (GIS) equipment observes surface charge accumulation under DC or AC voltage in real operation, which could distort the electric field and incur flashover eventually. With a 3D high-resolution surface charge measurement system established on actual 220 kV GIS basin insulator, the present research captured the surface charge distribution characteristics of the insulator under DC and AC voltage through high-precision probe scanning on the insulator surface. The test results show that: 1) Surface charge demonstrates obvious polarity effect under DC voltage. Under positive DC voltage, there accumulated mainly positive surface charges. Under negative DC voltage, the polarity of accumulated surface charges is all negative. Regardless of charge polarities, the surface charge density increases as the voltage amplitudes mounts and the voltage application duration prolongs. 2) Surface charge accumulation also takes place under AC voltage application. All charges are negative and distribute in a uniformed manner but in smaller density comparing to the DC scenario. As the voltage amplitudes increase, the surface charge density first increases, then decreases and finally reaches a near saturation state. As voltage application goes on, the surface charge accumulation becomes more obvious. Above all, the insulation issues in relation to surface charge accumulation require due attention in the application and maintenance of GIS equipment, and the present research attempts to provide useful reference for the optimal design of GIS/GIL insulators. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
12. Interface charge polarity effect based analysis model for electric field in oil-pressboard insulation under DC voltage.
- Author
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Qi, Bo, Gao, Chunjia, Zhao, Xiaolin, Li, Chengrong, and Wu, Hao
- Subjects
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ELECTRIC field strength , *KERR electro-optical effect , *ELECTRIC insulators & insulation , *POLARITY (Chemistry) , *ELECTRIC current converters , *ELECTRIC potential measurement - Abstract
The Resistive-Capacitive (RC) model has been widely adopted for analysis of the electric field in oil-pressboard insulation under DC voltage. However, studies in this regard have indicated that the charge polarity effect in oil-pressboard insulation, namely the stronger adsorption of negative charges by pressboard, could not be adequately captured by the RC model. In order to analyze the electric field with due consideration of charge polarity effect, the present paper adopted the Kerr electro-optic techniques to have measured the electric field in the oil spacing under DC voltage for two experiments models with Model I having two oil spacing divided by a pressboard at the spacing ratio of 1:1, and the Model II at the spacing ratio of 1:2. As Model I is concerned, the strength of electric field in the upper oil spacing reached 1.61 times of the initial one under positive voltage and 1.60 times under negative voltage, while the field in the lower oil spacing registered as one eighth of the initial one under both positive and negative voltages. For Model II, the electric field strength in the upper oil spacing reached 2.3 times of the initial field under positive voltage and one fourth of that under negative voltage, showing much stronger charge polarity effect compared to that in Model I. In order to analyze the effect of interface charge on electric field, an electric field analysis model based on interface charge, named Interface Charge Polarity Effect (ICPE) Model, is proposed in this paper. Referring to the different adhesive abilities of positive and negative charges on pressboard, the influence of interface charge on electric field can be analyzed by the proposed model, which could make the contribution to the insulating design and proofread for the converter transformer. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
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