The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fa...The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fault arc and pantograph-catenary arc.In this work,an experimental platform for the DC arc on the arcing horn was built,and mechanisms of the arc column short circuit and arc root movement were studied.This work further analyzes the characteristics and mechanisms of the arc motion when wind speed and direction,magnetic field and the expansion angle of the electrode are varied.Arc root movement is more likely to occur at the upper electrode.There is a competitive relationship between arc expansion and the transferring effect.The effect of wind on the arc column is greater than the effect on the arc root.The magnetic field has a significant driving effect on both the arc column and the arc root.The research results provide a comprehensive experimental basis for forther probing the method of DC arc suppression,and the improvement of the arcing horn.展开更多
After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission(QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing proce...After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission(QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing process and trend of ground temperature around tower foundations are crucial for the stability of QTPT. We analyzed the change characteristics and tendencies of the ground temperature based on field monitoring data from 2010 to 2014. The results reveal that soil around the tower foundations froze and connected with the artificial permafrost induced during the construction of footings after the first freezing period, and the soil below the original permafrost table kept freezing in subsequent thawing periods. The ground temperature lowered to that of natural fields, fast or slowly for tower foundations with thermosyphons,while for tower foundations without thermosyphons, the increase in ground temperature resulted in higher temperature than that of natural fields. Also, the permafrost temperature and ice content are significant factors that influence the ground temperature around tower foundations. Specifically, the ground temperature around tower foundations in warm and ice-rich permafrost regions decreased slowly, while that in cold and ice poor permafrost regions cooled faster. Moreover, foundations types impacted the ground temperature, which consisted of different technical processes during construction and variant of tower footing structures. The revealed changing process and trend of the ground temperature is beneficial for evaluating the thermal regime evolution around tower foundations in the context of climate change.展开更多
Delineation of the grounding line(GL) is necessary for calculating the mass balance of Antarctica, but GL measurements for most of the continent remain at a relatively coarse level. We used Sentinel-1 constellation da...Delineation of the grounding line(GL) is necessary for calculating the mass balance of Antarctica, but GL measurements for most of the continent remain at a relatively coarse level. We used Sentinel-1 constellation data to map the GL of the Amery Ice Shelf(AIS) using double-differential synthetic aperture radar interferometry. The ice thickness anomaly deduced from hydrostatic equilibrium and existing Antarctic GL products is compared with our result. With this new and very accurate GL, we detected new ice rises in the north of the AIS. Our new measurement shows no major change of the AIS GL, particularly in the southernmost part.展开更多
In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line select...In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line selection always existed in existing methods. According to the characteristics that transient current was different between the fault feeder and other faultless feeders, wavelet transformation was performed on data of the transient current within a power frequency cycle after the fault occurred. Based on different fault angles, wavelet energy in corresponding frequency band was chosen to compare. The result was that wavelet energy in fault feeder was the largest of all, and it was larger than sum of those in other faultless feeders, when the bus broke down, the disparity between each wavelet energy was not significant. Fault line could be selected out by the criterion above. The results of MATLAB/simulink simulation experiment indicated that this method had anti-interference capacity and was feasible.展开更多
The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR ground...The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm.If the fault disappears before LR is put into the system,it is judged as an instantaneous fault;while the fault does not disappear after LR is put into the system,it is judged as a permanent fault;the single-phase grounding fault(SLG)protection criterion based on zerosequence power variation is proposed to identify the instantaneous-permanent fault.Firstly,the distribution characteristic of zero-sequence voltage(ZSV)and zero-sequence current(ZSC)are analyzed after SLGfault occurs in multi-mode grounding.Then,according to the characteristics that zero-sequence power variation of non-fault collector line is small,while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance,the protection criterion based on zero-sequence power variation is constructed.The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information,which has high reliability.展开更多
Based on the monitoring data of cloud-to-ground( CG) lightning positioning network and Doppler weather radar as well as MICAPS1°× 1° objective analysis field,a squall line process outside of the subtrop...Based on the monitoring data of cloud-to-ground( CG) lightning positioning network and Doppler weather radar as well as MICAPS1°× 1° objective analysis field,a squall line process outside of the subtropical high in low-latitude plateau on May 7,2010 was analyzed. The results showed that wind direction shear between low and high levels and low-level convergence zones provided favorable circulation background for the strong thunderstorm process,while high energy and high humidity,strong thermal instability and ascending motion at low and middle levels offered beneficial environmental conditions for the formation of the thunderstorm. 9 620 return strokes of cloud-to-ground lightning were monitored by the lightning positioning network,and cloud-to-ground lightning was distributed like bands between 584 and 586 hP a. The occurrence of cloud-to-ground lightning was mainly related to echo top and echo intensity at-10 ℃ stratification height,and it mainly appeared in zones where echo top height was larger than 13 km and echo intensity at-10 ℃ stratification height was 35-40 dB Z. Wind convergence and maintaining of high radial velocity were favorable for the development of convective echoes and occurrence of cloud-to-ground lightning.展开更多
A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in this paper.A special d...A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in this paper.A special diagnostic signal current is injected into the fault distribution system,and then it is detected at the outlet terminals to identify the fault line and at the sectionalizing or branching point along the fault line to locate the fault section.The method has been put into application in actual distribution network and field experience shows that it can identify the fault line and locate the fault section correctly and effectively.展开更多
By means of improved ligand-field theory, the 'pure electronic' presure-induced shifts (PS's) and the PS's due to electron-phonon interaction (EPI) of the R1, R2, B1, B2, B3, and R'3 lines and the ...By means of improved ligand-field theory, the 'pure electronic' presure-induced shifts (PS's) and the PS's due to electron-phonon interaction (EPI) of the R1, R2, B1, B2, B3, and R'3 lines and the ground-state zero-field-splitting of ruby have been uniformly calculated. The calculation results are in very good agreement with all the experimental data. At normal pressure, ruby is a crystal with very strong crystal field. Thus, the admixture of |t22 (3T1)e4T2> and |t3 2 2 E> bases in the wavefunction of R1 level of ruby is small at normal pressure, and it gradually decreases with increasing pressure, which causes the R1-line PS of ruby to monotonously red shift with approximate linearity. The combined effect of the pure electronic PS of R1 line and the PS of R1 line due to EPI gives rise to the total PS of R1 line. The analyses and comparisons among the features of R1-line PS's of three laser crystals (ruby, GSGG:Cr3+ and GGG:Cr3+ ) have been made, and the origin of their difference has been revealed.展开更多
隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only ...隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only Look Once version 5)目标检测模型,结合数据集目标特征,提出一种检测衬砌空洞的算法,引入特征融合模块提高网络感受野,并采用K-means聚类算法提高检测准确率。通过现场检测,本文的检测方法准确率达到了97.7%,准确可靠,可在工程中进行应用。展开更多
基金National Natural Science Foundation of China(No.51907168)funded by Sichuan Science and Technology Program(Outstanding Youth Science and Technology Talents)(No.2020JDJQ0039)。
文摘The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fault arc and pantograph-catenary arc.In this work,an experimental platform for the DC arc on the arcing horn was built,and mechanisms of the arc column short circuit and arc root movement were studied.This work further analyzes the characteristics and mechanisms of the arc motion when wind speed and direction,magnetic field and the expansion angle of the electrode are varied.Arc root movement is more likely to occur at the upper electrode.There is a competitive relationship between arc expansion and the transferring effect.The effect of wind on the arc column is greater than the effect on the arc root.The magnetic field has a significant driving effect on both the arc column and the arc root.The research results provide a comprehensive experimental basis for forther probing the method of DC arc suppression,and the improvement of the arcing horn.
基金supported by National Natural Science Fund of China (Grant No. 41401088)State Grid Qinghai Electric Power Research Institute (SGQHDKYOSBJS201600077, SGQHDKYOSBJS 1700068)Funds of State Key Laboratory of Frozen Soil Engineering (Nos. SKLFSE-ZY-17, SKLFSEZT-32)
文摘After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission(QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing process and trend of ground temperature around tower foundations are crucial for the stability of QTPT. We analyzed the change characteristics and tendencies of the ground temperature based on field monitoring data from 2010 to 2014. The results reveal that soil around the tower foundations froze and connected with the artificial permafrost induced during the construction of footings after the first freezing period, and the soil below the original permafrost table kept freezing in subsequent thawing periods. The ground temperature lowered to that of natural fields, fast or slowly for tower foundations with thermosyphons,while for tower foundations without thermosyphons, the increase in ground temperature resulted in higher temperature than that of natural fields. Also, the permafrost temperature and ice content are significant factors that influence the ground temperature around tower foundations. Specifically, the ground temperature around tower foundations in warm and ice-rich permafrost regions decreased slowly, while that in cold and ice poor permafrost regions cooled faster. Moreover, foundations types impacted the ground temperature, which consisted of different technical processes during construction and variant of tower footing structures. The revealed changing process and trend of the ground temperature is beneficial for evaluating the thermal regime evolution around tower foundations in the context of climate change.
基金supported by National Program on Key Basic Research Project (Program 973, Grant no. 2013CBA01804)National Natural Science Foundation of China (Grant nos. 41531069 and 41376187)Chinese Polar Environment Comprehensive Investigation & Assessment Program (Grant no. CHINARE2016-02-04)
文摘Delineation of the grounding line(GL) is necessary for calculating the mass balance of Antarctica, but GL measurements for most of the continent remain at a relatively coarse level. We used Sentinel-1 constellation data to map the GL of the Amery Ice Shelf(AIS) using double-differential synthetic aperture radar interferometry. The ice thickness anomaly deduced from hydrostatic equilibrium and existing Antarctic GL products is compared with our result. With this new and very accurate GL, we detected new ice rises in the north of the AIS. Our new measurement shows no major change of the AIS GL, particularly in the southernmost part.
文摘In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line selection always existed in existing methods. According to the characteristics that transient current was different between the fault feeder and other faultless feeders, wavelet transformation was performed on data of the transient current within a power frequency cycle after the fault occurred. Based on different fault angles, wavelet energy in corresponding frequency band was chosen to compare. The result was that wavelet energy in fault feeder was the largest of all, and it was larger than sum of those in other faultless feeders, when the bus broke down, the disparity between each wavelet energy was not significant. Fault line could be selected out by the criterion above. The results of MATLAB/simulink simulation experiment indicated that this method had anti-interference capacity and was feasible.
基金This paper is supported in part by the National Natural Science Foundations of China,and the Major Science and Technology Projects in Yunnan Province under Grant Nos.51667010,51807085,and 202002AF080001.
文摘The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm.If the fault disappears before LR is put into the system,it is judged as an instantaneous fault;while the fault does not disappear after LR is put into the system,it is judged as a permanent fault;the single-phase grounding fault(SLG)protection criterion based on zerosequence power variation is proposed to identify the instantaneous-permanent fault.Firstly,the distribution characteristic of zero-sequence voltage(ZSV)and zero-sequence current(ZSC)are analyzed after SLGfault occurs in multi-mode grounding.Then,according to the characteristics that zero-sequence power variation of non-fault collector line is small,while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance,the protection criterion based on zero-sequence power variation is constructed.The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information,which has high reliability.
基金Supported by National Natural Science Foundation of China(No.41305002)Science and Technology Project of Yunnan Province(No.2014RA002,2016RA096)
文摘Based on the monitoring data of cloud-to-ground( CG) lightning positioning network and Doppler weather radar as well as MICAPS1°× 1° objective analysis field,a squall line process outside of the subtropical high in low-latitude plateau on May 7,2010 was analyzed. The results showed that wind direction shear between low and high levels and low-level convergence zones provided favorable circulation background for the strong thunderstorm process,while high energy and high humidity,strong thermal instability and ascending motion at low and middle levels offered beneficial environmental conditions for the formation of the thunderstorm. 9 620 return strokes of cloud-to-ground lightning were monitored by the lightning positioning network,and cloud-to-ground lightning was distributed like bands between 584 and 586 hP a. The occurrence of cloud-to-ground lightning was mainly related to echo top and echo intensity at-10 ℃ stratification height,and it mainly appeared in zones where echo top height was larger than 13 km and echo intensity at-10 ℃ stratification height was 35-40 dB Z. Wind convergence and maintaining of high radial velocity were favorable for the development of convective echoes and occurrence of cloud-to-ground lightning.
基金Postdoctoral Foundation of China(No.20070410755)PAN Zhencun,born in 1962,male,postdoctor researcher.
文摘A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in this paper.A special diagnostic signal current is injected into the fault distribution system,and then it is detected at the outlet terminals to identify the fault line and at the sectionalizing or branching point along the fault line to locate the fault section.The method has been put into application in actual distribution network and field experience shows that it can identify the fault line and locate the fault section correctly and effectively.
文摘By means of improved ligand-field theory, the 'pure electronic' presure-induced shifts (PS's) and the PS's due to electron-phonon interaction (EPI) of the R1, R2, B1, B2, B3, and R'3 lines and the ground-state zero-field-splitting of ruby have been uniformly calculated. The calculation results are in very good agreement with all the experimental data. At normal pressure, ruby is a crystal with very strong crystal field. Thus, the admixture of |t22 (3T1)e4T2> and |t3 2 2 E> bases in the wavefunction of R1 level of ruby is small at normal pressure, and it gradually decreases with increasing pressure, which causes the R1-line PS of ruby to monotonously red shift with approximate linearity. The combined effect of the pure electronic PS of R1 line and the PS of R1 line due to EPI gives rise to the total PS of R1 line. The analyses and comparisons among the features of R1-line PS's of three laser crystals (ruby, GSGG:Cr3+ and GGG:Cr3+ ) have been made, and the origin of their difference has been revealed.
文摘隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only Look Once version 5)目标检测模型,结合数据集目标特征,提出一种检测衬砌空洞的算法,引入特征融合模块提高网络感受野,并采用K-means聚类算法提高检测准确率。通过现场检测,本文的检测方法准确率达到了97.7%,准确可靠,可在工程中进行应用。