Aging effect analysis of long period operating composite insulators in different electric field position

Yun-Peng Liu 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.S1

Electric field distribution is one of the important factors which impact the aging of composite insulators. The electric field of composite insulators was simulated by ANSYS software, and the shed samples in different parts of the composite insulator were analyzed by Fourier transform infrared spectroscopy (FTIR). The characteristic peaks of functional groups in the main chain and side chain of composite insulator material molecular formula were compared. The smaller the characteristic peak area is, the less the corresponding functional group is, that means the facture condition of main chain or side chain is more serious. In this way, the characteristic peaks of samples in different electric field distribution were compared, and the influence of electric field distribution to the aging effect of the composite insulators is gained. The results show that electric field strength is the strongest in the composite insulator high-voltage side, followed by lowvoltage side, and the electric field in the middle of the composite insulator is the lowest. Accordingly, the aging degree in the composite insulator high-voltage side is the most serious, followed by low-voltage side, and the aging degree is weakest in the middle part.

Influence of Endurance tests on Space Charge Distribution of 160kV HVDC XLPE Cable

Yun-Peng Liu,He-Chen Liu 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

The ageing of XLPE cable insulation will lead to the accelerating accumulation of space charge, which will greatly affect the safe operation of the HVDC cable. In order to investigate the influence of different ageing modes on the space charge distribution of the HVDC cable, thermal stressed, electrical stressed and electro-thermal stressed endurance tests were carried out on the XLPE peelings. The tested XLPE peelings were obtained from 160kV HVDC cable insulation. The endurance tests were carried at thermal stress of 363K, electrical stress of 20kV/mm DC and a combination of both. The Pulsed Electro-Acoustic (PEA) method was used to measure the space charge distribution of the samples. The influences of ageing on the trap energy distribution were analyzed based on the isothermal relaxation theory and the decay characteristics of the space charge. The results showed that thermal ageing would help to improve the crystalline morphologies of the XLPE at the early stage. The total amount of space charge decreased compared to the ones before thermal ageing. The long term of electrical stress would result in the cleavage of polymer molecule chains which would intensify the accumulation of space charge and increase the density and depth of electron traps. With a combination of electrical and thermal stress, the injection and migration of space charge were more significant. Besides, the depth and density of electron traps increased rapidly with the increase of endurance time.

Corona generated Radio Interference of the 750 kV AC Bundle Conductors in Sandy and Dusty Weather Condition in the High Altitude Area

Yun-Peng Liu,Lei Zhu,Fang-Cheng Lv,Bao-Quan Wan,Chun-Ming Pei 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.5

Sandy and dusty weather condition often occurs in the high altitude areas of China, which may greatly influence the corona generated radio interference (RI) characteristics of the bundle conductors of 750 kV AC power transmission lines. Corona generated RI of the conductors of the 750 kV AC power transmission lines used in practice is measured by EMI receiver with a coupling circuit and a coupling capacitor connected between the high voltage side and the earth side in fine and sandy and dusty condition. The measuring frequency is 0.5 MHz, and the quasi-peak detection is used. RI excitation function is calculated based on the corona RI current measured by the EMI receiver. Corona generated RI characteristics were analyzed from sand concentration and sand particle size. The test result shows that the corona generated RI excitation function is influenced by the sandy and dusty condition. Corona discharge of the conductors is more serious in sandy and dusty condition with an ultraviolet (UV) detector. Corona generated RI excitation function increases with the increase of sand concentration and also increases with the increase of particle size.

A Weibo Topic Tracking System based on K-means

Yun Liu,Kun-Peng Xia,Jian-Xun Zhao 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.6

This article studied weibo text representation. For the weibo features such as short, real-time, colloquialism and originality, in the original vector space model, we propose a suitable method for weibo text representation. Make all the content words as feature words after participation. And we proposed T-TFIDF weight calculation method according to the features of weibo. According to the vector space model, we proposed a weibo adaptive topic tracking methods based on K-means clustering. Simulation analysis shows that, the method can by comparing the similarity micro-blog and sub topic vector set, determine whether weibo belonging to the topic.

Negative Corona Onset Characteristic of the UHV Conductors Based on the Corona Cage

Yun-Peng Liu,Lei Zhu,Fang-Cheng Lv,Xiongjie Xie 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.6

Negative corona onset characteristics of the stranded conductors based on the ultra-high voltage (UHV) corona cage were studied in the paper. Based on the corona self-sustaining criterion in extreme uneven electric fields and the secondary emission process of the photoelectrons, the corona onset calculation model in the UHV corona cage is established and the corona current tests of the single LGJ900-75, 6 bundle LGJ900-75, 8 bundle LGJ400-35 conductors in dry and rain conditions were done in the UHV corona cage, and the rain rates are 2.4 mm/h, 20 mm/h and 30 mm/h. Corona onset electric field strength is gained by E-I tangent method, and the onset electric field strength in dry condition proves that the calculation model can be used to calculate the corona onset characteristics of the bundle conductors in the UHV corona cage. A further analysis proves that: the negative corona onset voltage of the conductor increases with the bundle number and the diameter of the sub conductor, but decreases with the bundle space in the corona cage. The onset electric field strength is influenced little by bundle space and bundle number, but decreases with the increase of the diameter of the sub-conductor. The surface irregularity coefficient decreases with the rain rate.

Experimental Investigation of Ion Mobility Measurements in Oxygen under Different Gas Pressures

Liu, Yun-Peng,Huang, Shi-long The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.2

In this paper, measurements of ion mobility were performed in oxygen at gas pressures of 44.52 - 101.19 kPa using the drift tube method. Over this pressure range, mobility values were within the limits of 1.796 to $3.821cm^2{\cdot}V^{-1}{\cdot}s^{-1}$ were determined and ion mobility shown to decrease non-linearly with increasing gas pressure towards a certain level of saturation. Ion mobility measured in air was lower than that measured in oxygen at the same gas pressure. Finally, a parameter correction method for calibrating the relationship between the ion mobility and gas pressure in oxygen was proposed.

Experimental Investigation of Ion Mobility Measurements in Oxygen under Different Gas Pressures

Yun-Peng Liu,Shi-long Huang 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.2

In this paper, measurements of ion mobility were performed in oxygen at gas pressures of 44.52 - 101.19 kPa using the drift tube method. Over this pressure range, mobility values were within the limits of 1.796 to 3.821 ㎠·V<SUP>-1</SUP>·s<SUP>-1</SUP> were determined and ion mobility shown to decrease nonlinearly with increasing gas pressure towards a certain level of saturation. Ion mobility measured in air was lower than that measured in oxygen at the same gas pressure. Finally, a parameter correction method for calibrating the relationship between the ion mobility and gas pressure in oxygen was proposed.

The Structural Design of Tianjin Goldin Finance 117 Tower

Liu, Peng,Ho, Goman,Lee, Alexis,Yin, Chao,Lee, Kevin,Liu, Guang-lei,Huang, Xiao-yun Council on Tall Building and Urban Habitat Korea 2012 International journal of high-rise buildings Vol.1 No.4

Tianjin Goldin Finance 117 tower has an architectural height of 597 m, total of 117 stories, and the coronation of having the highest structural roof of all the buildings under construction in China. Structural height-width ratio is approximately 9.5, exceeding the existing regulation code significantly. In order to satisfy earthquake and wind-resisting requirements, a structure consisting of a perimeter frame composed of mega composite columns, mega braces and transfer trusses and reinforced concrete core containing composite steel plate wall is adopted. Complemented by some of the new requirements from the latest Chinese building seismic design codes, design of the super high-rise building in high-intensity seismic area exhibits a number of new features and solutions to professional requirements in response spectrum selection, overall stiffness control, material and component type selection, seismic performance based design, mega-column design, anti-collapse and stability analysis as well as elastic-plastic time-history analysis. Furthermore, under the prerequisite of economic viability and a series of technical requirements prescribed by the expert review panel for high-rise buildings exceeding code limits, the design manages to overcome various structural challenges and realizes the intentions of the architect and the client.

Negative Corona Onset Characteristic of the UHV Conductors Based on the Corona Cage

Liu, Yun-Peng,Zhu, Lei,Lv, Fang-Cheng,Xie, Xiongjie The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.6

Negative corona onset characteristics of the stranded conductors based on the ultra-high voltage (UHV) corona cage were studied in the paper. Based on the corona self-sustaining criterion in extreme uneven electric fields and the secondary emission process of the photoelectrons, the corona onset calculation model in the UHV corona cage is established and the corona current tests of the single LGJ900-75, 6 bundle LGJ900-75, 8 bundle LGJ400-35 conductors in dry and rain conditions were done in the UHV corona cage, and the rain rates are 2.4 mm/h, 20 mm/h and 30 mm/h. Corona onset electric field strength is gained by E-I tangent method, and the onset electric field strength in dry condition proves that the calculation model can be used to calculate the corona onset characteristics of the bundle conductors in the UHV corona cage. A further analysis proves that: the negative corona onset voltage of the conductor increases with the bundle number and the diameter of the sub conductor, but decreases with the bundle space in the corona cage. The onset electric field strength is influenced little by bundle space and bundle number, but decreases with the increase of the diameter of the sub-conductor. The surface irregularity coefficient decreases with the rain rate.

Corona generated Radio Interference of the 750 kV AC Bundle Conductors in Sandy and Dusty Weather Condition in the High Altitude Area

Liu, Yun-Peng,Zhu, Lei,Lv, Fang-Cheng,Wan, Bao-Quan,Pei, Chun-Ming The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.5

Sandy and dusty weather condition often occurs in the high altitude areas of China, which may greatly influence the corona generated radio interference (RI) characteristics of the bundle conductors of 750 kV AC power transmission lines. Corona generated RI of the conductors of the 750 kV AC power transmission lines used in practice is measured by EMI receiver with a coupling circuit and a coupling capacitor connected between the high voltage side and the earth side in fine and sandy and dusty condition. The measuring frequency is 0.5 MHz, and the quasi-peak detection is used. RI excitation function is calculated based on the corona RI current measured by the EMI receiver. Corona generated RI characteristics were analyzed from sand concentration and sand particle size. The test result shows that the corona generated RI excitation function is influenced by the sandy and dusty condition. Corona discharge of the conductors is more serious in sandy and dusty condition with an ultraviolet (UV) detector. Corona generated RI excitation function increases with the increase of sand concentration and also increases with the increase of particle size.