Research on Liquefaction Characteristics of SF6 Substitute Gases

Zhikang Yuan,Youping Tu,Cong Wang,Sichen Qin,Geng Chen 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

SF₆ has been widely used in high voltage power equipment, such as gas insulated switchgear (GIS) and gas insulated transmission line (GIL), because of its excellent insulation and arc extinguishing performance. However, SF₆ faces two environmental problems: greenhouse effect and high liquefaction temperature. Therefore, to find the SF₆ substitute gases has become a research hotspot in recent years. In this paper, the liquefaction characteristics of SF₆ substitute gases were studied. Peng–Robinson equation of state with the van der Waals mixing rule (PR-vdW model) was used to calculate the dew point temperature of the binary gas mixtures, with SF₆, C₃F₈, c-C₄F₈, CF₃I or C₄F₇N as the insulating gas and N₂ or CO₂ as the buffer gas. The sequence of the dew point temperatures of the binary gas mixtures under the same pressure and composition ratio was obtained. SF₆/N₂ < SF₆/CO₂ < C₃F₈/N₂ < C₃F₈/CO₂ < CF₃I/N₂ < CF₃I/CO₂ < c-C₄F₈/N₂ < C₄F₇N/N₂ < c-C₄F₈/CO₂ <C₄F₇N/CO₂. SF₆/N₂ gas mixture showed the best temperature adaptability and C₄F₇N/CO₂ gas mixture showed the worst temperature adaptability. Furthermore, the dew point temperatures of the SF₆ substitute gases at different pressures and the upper limits of the insulating gas mole fraction at -30℃, -20℃ and -10℃ were obtained. The results would supply sufficient data support for GIS/GIL operators and researchers.

Research on Liquefaction Characteristics of SF6 Substitute Gases

Yuan, Zhikang,Tu, Youping,Wang, Cong,Qin, Sichen,Chen, Geng The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

$SF_6$ has been widely used in high voltage power equipment, such as gas insulated switchgear (GIS) and gas insulated transmission line (GIL), because of its excellent insulation and arc extinguishing performance. However, $SF_6$ faces two environmental problems: greenhouse effect and high liquefaction temperature. Therefore, to find the $SF_6$ substitute gases has become a research hotspot in recent years. In this paper, the liquefaction characteristics of $SF_6$ substitute gases were studied. Peng-Robinson equation of state with the van der Waals mixing rule (PR-vdW model) was used to calculate the dew point temperature of the binary gas mixtures, with $SF_6$, $C_3F_8$, $c-C_4F_8$, $CF_3I$ or $C_4F_7N$ as the insulating gas and $N_2$ or $CO_2$ as the buffer gas. The sequence of the dew point temperatures of the binary gas mixtures under the same pressure and composition ratio was obtained. $SF_6/N_2$ < $SF_6/CO_2$ < $C_3F_8/N_2$ < $C_3F_8/CO_2$ < $CF_3I/N_2$ < $CF_3I/CO_2$ < $c-C_4F_8/N_2$ < $C_4F_7N/N_2$ < $c-C_4F_8/CO_2$ < $C_4F_7N/CO_2$. $SF_6/N_2$ gas mixture showed the best temperature adaptability and $C_4F_7N/CO_2$ gas mixture showed the worst temperature adaptability. Furthermore, the dew point temperatures of the $SF_6$ substitute gases at different pressures and the upper limits of the insulating gas mole fraction at $-30^{\circ}C$, $-20^{\circ}C$ and $-10^{\circ}C$ were obtained. The results would supply sufficient data support for GIS/GIL operators and researchers.

Analysis on Temperature Distribution and Current-Carrying Capacity of GIL Filled with Fluoronitriles-CO₂ Gas Mixture

Geng Chen,Youping Tu,Cong Wang,Yi Cheng,Han Jiang,Hongyang Zhou,Hua Jin 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

Fluoronitriles-CO₂ gas mixtures are promising alternatives to SF6 in environmentallyfriendly gas-insulated transmission lines (GILs). Insulating gas heat transfer characteristics are of major significance for the current-carrying capacity design and operational state monitoring of GILs. In this paper, a three-dimensional calculation model was established for a GIL using the thermal-fluid coupled finite element method. The calculated results showed close agreement with experimentally measured data. The temperature distribution of a GIL filled with the Fluoronitriles-CO₂ mixture was obtained and compared with those of GILs filled with CO₂ and SF6. Furthermore, the effects of the mixture ratio of the component gases and the gas pressure on the temperature rise and current-carrying capacity of the GIL were analyzed. Results indicated that the heat transfer performance of the Fluoronitriles-CO₂ gas mixture was better than that of CO₂ but worse than that of SF₆. When compared with SF6, use of the Fluoronitriles-CO₂ gas mixture caused a reduction in the GIL’s current-carrying capacity. In addition, increasing the Fluoronitriles gas component ratio or increasing the pressure of the insulating gas mixture could improve the heat dissipation and current-carrying capacity of the GIL. These research results can be used to design environmentally-friendly GILs containing Fluoronitriles-CO₂ gas mixtures.

Numeral analysis model for shielding failure of transmission line under lightning stroke

He, Jinliang,Tu, Youping,Zeng, Rong,Lee, J.B.,Chang, S.H.,Guan, Zhicheng IEEE 2005 IEEE transactions on power delivery Vol.20 No.2

The shielding failure is the occurrence of a lightning stroke that bypasses the overhead ground wires and terminates on the phase conductors. The correct design to improve the shielding effect of transmission line to lightning is one of the key problems of transmission line design. A numerical analysis model for shielding failure of transmission line based on electromagnetic field theory is proposed in this paper. The electrical field of the system including lightning leader, transmission line and ground is solved, the range of lightning current striking the phase conductor is obtained, and the shielding failure probability of transmission line is calculated. The lightning leader model and the critical breakdown electrical field intensity of long gap are discussed. The analyzed results by numerical analysis model are compared with those by the electrogeometric model.

Analysis on Temperature Distribution and Current-Carrying Capacity of GIL Filled with Fluoronitriles-CO₂ Gas Mixture

Chen, Geng,Tu, Youping,Wang, Cong,Cheng, Yi,Jiang, Han,Zhou, Hongyang,Jin, Hua The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

Fluoronitriles-$CO_2$ gas mixtures are promising alternatives to $SF_6$ in environmentally-friendly gas-insulated transmission lines (GILs). Insulating gas heat transfer characteristics are of major significance for the current-carrying capacity design and operational state monitoring of GILs. In this paper, a three-dimensional calculation model was established for a GIL using the thermal-fluid coupled finite element method. The calculated results showed close agreement with experimentally measured data. The temperature distribution of a GIL filled with the Fluoronitriles-$CO_2$ mixture was obtained and compared with those of GILs filled with $CO_2$ and $SF_6$. Furthermore, the effects of the mixture ratio of the component gases and the gas pressure on the temperature rise and current-carrying capacity of the GIL were analyzed. Results indicated that the heat transfer performance of the Fluoronitriles-$CO_2$ gas mixture was better than that of $CO_2$ but worse than that of $SF_6$. When compared with $SF_6$, use of the Fluoronitriles-$CO_2$ gas mixture caused a reduction in the GIL's current-carrying capacity. In addition, increasing the Fluoronitriles gas component ratio or increasing the pressure of the insulating gas mixture could improve the heat dissipation and current-carrying capacity of the GIL. These research results can be used to design environmentally-friendly GILs containing Fluoronitriles-$CO_2$ gas mixtures.

Influence of overhead transmission line on grounding impedance measurement of substation

Zeng, Rong,He, Jinliang,Lee, Jaebok,Chang, S.,Tu, Youping,Gao, Yanqing,Zou, Jun,Guan, Zhicheng IEEE 2005 IEEE transactions on power delivery Vol.20 No.2

How to precisely measure the grounding impedance of large-scale substations is a fundamental guarantee for the safe operation of power systems. If the ground wires were connected to the grounding grid, these ground wires would shunt a part of the injected measuring current and allow the measured grounding impedance to be smaller than the actual impedance of the grounding system. Based on an actual 500-kV grounding system, this paper discusses how to analyze the influence of the overhead ground wire on the measured grounding impedance and how to obtain the real grounding impedance of the grounding system. A numerical analysis model considering the grounding system, the transmission lines, towers, and their grounding devices, based on the multilayer soil model analyzed from field test data of apparent soil resistivity, was constructed to analyze the influence of ground wires and tower grounding resistances on grounding impedance, and the general effects of different parameters, such as tower impedance, grounding impedance, and circuits of transmission lines, were analyzed. The real grounding impedance of the substation with connected overhead ground wires was validated, and some useful results have been obtained, based on the field-measured values and numerical analysis.