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34 results on '"Wu, Jingfeng"'

9. Research on Field Electromagnetic Compatibility Test Method of System Level for Electronic Transformers

Author

Guo Anxiang, Wu Zihao, Haodong Xu, Wang Chenxi, Lin Cheng, Cheng Zhang, Wu Jingfeng, Wei Haokun, and Jiangping Lu

Subjects
Electromagnetic field, Secondary side, Computer science, business.industry, law, Electrical engineering, Electromagnetic compatibility, System level, Type test, Test method, business, Transformer, law.invention
Abstract

The existing current standards for electronic transformers are formulated based on the equivalent of traditional electromagnetic transformers and secondary side protection equipments. In this situation, Although these products have can passed the type test, but there are still a large number of electromagnetic compatibility (EMC) problems still appeared in actual operation. In this paper, based on the actual field application, the interference mechanism of the AIS isolating switch and the electromagnetic transient process on the electronic transformers is simulated. The interference model of the transient electromagnetic field to the secondary side of the electronic transformers and the transmission cables are obtained. Then, a field system-level EMC test method of electronic transformers is proposed. This method is based on the actual equipment and wiring conditions in substations, and the anti-strong electromagnetic disturbance ability of the electronic transformers is evaluated under the condition of “conventional” or “unconventional” operations. Finally, Finally, the field application of system-level electromagnetic compatibility test was carried out in the 330kV Xinsheng Substation, and the fault electronic transformer was tested, which proved the effectiveness of the method.

Published
2018

13. Interface Charge Barrier between Oil and Oil Immersed Paper.

Author

Cheng, Chuanhui, Wu, Kai, Fu, Mingli, Hao, YanPeng, Ren, Shuangzan, Wu, Jingfeng, and Wu, Hao

Subjects
ELECTRIC double layer, PETROLEUM, ZETA potential
Abstract

This paper presents an investigation of the underlying mechanism behind the interface charge barrier between oil and oil immersed paper. Two types of oils and two types of cellulose papers are selected in the study. The interface charges of the samples are measured by the pulsed electro-acoustic (PEA) method and the zeta potentials of different oil-paper combinations are also measured. The results show that the amount of interface charge changes with the type of oils and papers, and is much larger than the Maxwell-Wagner-Sillars (MWS) polarization charge. The difference in the amount of interface charges cannot be attributed to the difference in the conductivity and permittivity of the materials. It is suggested that the barrier for charge transport across the interface, which is formed due to the electric double layer, should be taken into consideration to explain the interface charge behavior in oil-paper insulation. [ABSTRACT FROM AUTHOR]

Published
2021
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14. Distinction between the Contributions of Ionized and Injected Charges in Oil Immersed Paper.

Author

Wu, Yang, Wu, Kai, Cheng, Chuanhui, Su, Rui, Lv, Zepeng, Ren, Shuangzan, Wu, Jingfeng, and Wu, Hao

Subjects
PETROLEUM, IONIC mobility, ELECTRIC fields, SPACE charge, CHARGE measurement
Abstract

This paper proposes a method of distinguishing the contributions of ionized and injected charges to the charge transport in oil immersed paper in triple-layer and double-layer samples. With the double-layer sample, the apparent mobility including the ions contribution is obtained by the calculation according to the speed of accumulated charge density at the interface. The contribution of ions is excluded by subtracting the accumulated charge density in the triple-layer sample from that in the double-layer sample. It is found that the interface charge mainly comes from the ionization charges under a low field, and the contribution of injected charge takes a more important part at higher electric field. [ABSTRACT FROM AUTHOR]

Published
2021
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17. Dynamic condition vector assessment method for electric power equipment of overall process: Novel and necessary technical approach of condition-based-assessment

Author

Liu, Yang, primary, Qi, Weidong, additional, Wu, Jingfeng, additional, Pu, Lu, additional, Wang, Sen, additional, Han, Yanhua, additional, Yang, Chuankai, additional, Cheng, Lin, additional, Liu, Wei, additional, Li, Xu, additional, Li, Liangshu, additional, and Shi, Yiqing, additional

Published
2017
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18. Drawing method of frequency division fault maps for GIS partial discharge based on ultra-high frequency signals

Author

Jing Wang, Wu Jingfeng, Xiao-Lan Zhang, Weidong Qi, Guo-Qiang Huang, and Bo Niu

Subjects
Engineering, business.industry, Fault (power engineering), Interference (wave propagation), Time–frequency analysis, Frequency divider, Ultra high frequency, Physics::Plasma Physics, Partial discharge, Electronic engineering, Point (geometry), business, Algorithm, Effective frequency
Abstract

This paper proposes a drawing method of frequency division fault maps for GIS partial discharge based on Ultra-high Frequency signals. By extracting Ultra-high Frequency partial discharge signals and filtering adaptively, interference signals are filtered out real-timely, and the effective frequency sequence is obtained adaptively. The characteristic quantity of each effective frequency point is calculated, and then dynamic fault map varying with effective frequency points, characteristics trend map for frequency division discharge and quantity trend map for effective frequency points are drawn. Compared with current fault maps for GIS partial discharge, test results show that the discharge law for different frequency points is drawn by contacting effective frequency points with partial discharge law proposed in this paper, which is helpful for research on discharge law with the frequency.

Published
2016

31. Influence of Axial Magnetic Field on Cathode Plasma Jets in High-Current Vaccum Arc.

Author

Yang, Dingge, Jia, Shenli, Qi, Weidong, Wu, Jingfeng, Wang, Sen, Han, Yanhua, Ding, Bin, Zhang, Heng, and Li, Wenhui

Subjects
PLASMA jets, MAGNETIC fields, PLASMA arcs, ELECTROCHEMICAL electrodes, PLASMA stability
Abstract

The cathode plasma jets in vacuum arc and the effect of magnetic field on them have been studied for several years and these studies are helpful to understand the arc characteristics and improve the controlling effect of magnetic field on arc plasma. In this paper, the experiments of the cup-shaped axial magnetic field (AMF) contacts were conducted in which a Helmholtz coil was introduced to generate different external imposed AMFs. It was found that the appearance of arc plasma was changed by variation of the external imposed AMF. If the composite AMF in arc column increased gradually, the obvious individual cathode plasma jets were detected, the arc constriction decreased, and the arc stability increased. Meanwhile, the inclination of cathode plasma jets was observed and the inclination direction was found to be consistent with the magnetic field vector direction which is closely related to the composite AMF. By variation of the external imposed AMF and its direction, the inclination direction of cathode plasma jets also changed. The criterion to detect obvious cathode jets in arc column is obtained that at the contact peripheral where R> 80.5% R0 (R0 is the contact radius), the AMF strength is no less than 4.5 mT/kA. It was also found that if the composite AMF in interelectrode gap points to different directions at a certain moment, it may lead to the transfer of arc column from the center to the edge of the interelectrode region and the arc instability until when the composite AMF in the interelectrode gap points to the same direction. It can be concluded that the appearance of individual cathode plasma jets can be manipulated by the variation of AMF, which is helpful to study the interaction between arc plasma and electrodes, especially the anode, and improve the interruption performance at higher current. [ABSTRACT FROM PUBLISHER]

Published
2017
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