Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning imp...Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.展开更多
This paper has researched the insulation characteristics of 10% c-C4F8/N2/CO2 mixtures under lightning impulse voltage by experiment. It is shown that the positive and negative lightning impulse breakdown voltages of ...This paper has researched the insulation characteristics of 10% c-C4F8/N2/CO2 mixtures under lightning impulse voltage by experiment. It is shown that the positive and negative lightning impulse breakdown voltages of 10%c-C4F8/N2/CO2 gas mixtures rise linearly as the electrode gap distance and gas pressure increase and under the same conditions, the positive lightning impulse breakdown voltage of the gas mixtures is always higher than the negative lightning impulse breakdown voltage. As the gas mixtures have a little higher liquefied temperature than SF6 and the comprehensive GWP is about 5% of SF6, and the positive and negative lightning impulse breakdown voltages can both reach 60% of SF6, 10%c-C4F8/N2/CO2 gas mixtures can be applied as insulation gas in electrical equipment such as C-GIS, GIT, GIL and so on.展开更多
Transient over voltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus,like circuit breakers,transformers,insulators etc.Therefore it is nece...Transient over voltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus,like circuit breakers,transformers,insulators etc.Therefore it is necessary for the GIS also to withstand such voltages without breakdown of Insulation.The system has to be tested under these conditions.Usually the GIS system operates on power frequency.Lightning Impulse Voltage of 1050 kV and Switching Impulse Voltage of 750 kV superimposed on Power frequency voltages of 75 kV,100 kV and 132 kV are applied to Single Phase Gas Insulated Busduct and the maximum movement of Aluminum,Copper and Silver particles is determined.The movement patterns are also determined with and without Monte Carlo Simulation for movement of particle in axial and radial directions.The results show that there is a sudden jump in the movement at the application of impulse on sine wave.This is because of high magnitude voltage of 1050 kV during 1.2/50 μs.Similar movement patterns of reduced maximum movement is observed for Switching Impulse superimposed on sine wave.The results are presented and analyzed.展开更多
Looking at the problem of electrical discharge development in mineral oil, it is easy to see that most studies in this area focused on the setups of bare high voltage electrodes having a point-plane electrode arrangem...Looking at the problem of electrical discharge development in mineral oil, it is easy to see that most studies in this area focused on the setups of bare high voltage electrodes having a point-plane electrode arrangement. The setups with insulated electrodes are the mar- gin of these studies but it seems to be important to find the dependences between the paper insulation on high voltage electrode and parameters of the discharges initiated in the vicinity of this electrode. Hence, in this paper the results of researches intended to reveal the role of insulation wrapping on a HV electrode in the mechanism of electrical discharges in transformer oil under lightning impulse of both polar- ities are presented. This role is determined by analysis of the parameters characterizing the discharges (onset voltage, propagation velocity, time to initiation, rise-time of light impulses) and also by observation of their spatio-temporal development and oscillograms of the light emitted by their channels. The research was performed for two model electrode configurations: an electrode with paper insulation and a bare electrode which had the same outer dimensions as the insulated one. The most essential conclusion from performed experiment is related to times to initiation. These times, equal in the case of insulated electrodes and model bare electrode, indicate that the source of "weak points" of the paper-oil insulation system is the oil, not the surface of insulation wrapping or the metal.展开更多
The Lightning Mapping Imager(LMI)equipped on the FY-4 A(Feng Yun-4 A)geostationary satellite achieves lightning positioning through optical imaging and has the advantages of high temporal resolution,high stability,and...The Lightning Mapping Imager(LMI)equipped on the FY-4 A(Feng Yun-4 A)geostationary satellite achieves lightning positioning through optical imaging and has the advantages of high temporal resolution,high stability,and continuous observation.In this study,FY-4 A LMI lightning event,group and flash data from April to August 2018 are selected,and their quality are assessed through qualitative and quantitative comparison with the ground-based Advanced Time of Arrival and Direction system(ADTD)lightning observation network data and the American International Space Station(ISS)lightning imaging sensor(LIS)data.The results show that the spatial distributions of FY-4 A lightning are consistent with those of the ground-based ADTD and ISS LIS.The temporal variation in FY-4 A lightning group frequency is consistent with that of ADTD stroke,which reflects that FY-4 A LMI can capture the lightning occurrence in inland China.Quantitative statistics show that the consistency rate of FY-4 A LMI and ISS LIS events is relatively high but their consistency rate is lower in terms of lightning group and flash data.Compared with the lightning observations by the ISS LIS and the ground-based ADTD,FY-4 A LMI reports fewer lightning events in the Tibetan Plateau.The application of Tibetan Plateau lightning data requires further processing and consideration.展开更多
When the tower overhead is struck by the lightning impulse, the lightning current flows into the earth through the impedance of tower and the grounding resistance, which heightens potential of the tower overhead and p...When the tower overhead is struck by the lightning impulse, the lightning current flows into the earth through the impedance of tower and the grounding resistance, which heightens potential of the tower overhead and possibly induces insulator flashover. Lighting rod arrester is used to shield the tower and provide another routine for lightning current, decreasing the potential of tower overhead. In this paper, the performance of a 500 kV lighting rod arrester is tested used in AC transmission system under the current impulse. Besides, the influence of the lightning rod arrester performance on the top potential of tower is also studied. The results show that, when the rod arrester is connected to the tower, the top potential of tower can be obviously limited under the lightning strike.展开更多
This paper analyzes the effects of the voltage across insulator of 69 kV and 24 kV lines installed on the same pole. The case studies illustrated the lightning strike to direct top pole and mid span of ground wire usi...This paper analyzes the effects of the voltage across insulator of 69 kV and 24 kV lines installed on the same pole. The case studies illustrated the lightning strike to direct top pole and mid span of ground wire using the ATP-EMTP （Alternative Transient Program-Electromagnetic Transient Program）. The results found that when lightning strike the voltage across the 69 kV line insulator at mid span is 1.55 times and 1.34 times higher than at top pole when the front time is 0.25/100μs and 10/350 μs, respectively. When lightning strike the voltage across the 24 kV line at mid span is 1.04 times and 0.64 times higher than at top pole when the front time is 0.25/100μs and 10/350μs, respectively. So the effect of lightning strike is more severe at mid span than at the direct top pole, especially for the 69 kV insulator.展开更多
The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteri...The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteristics of steel and investigating the impact of anti-corrosion coating on these characteristics. Ablation characteristics were investigated through the macroscopic morphology and x-ray diffraction patterns on the surface of damaged zones, the microstructure and micro Vickers hardness on the cross-section of damaged zones, and the maximum rear-face temperature of sample sheets. It can be concluded that the ablation areas of uncoated sheet consist of the melted layer and the heat-affect layer. These ablation areas include not only the area ablated directly by the arc root, of which the depth is deeper, but also the area forming due to the splashing of molten steel, of which the depth is shallower and decreases when the area’s distance from the arc attachment point increases. For coated sheet, coating materials have decomposed and evaporated forming an ablation pit on the sheet surface, in which the steel surface is exposed, and zinc filler of coating primer has infused into the exposed surface. The ablation diameter of uncoated sheet relates to the amplitude of the 30/80 μs impulse current in quadratic function, while for coated sheet, the relation is linear. In general, under the 30/80 μs impulse current, the coating can decrease the energy injected from the arc to the steel sheet and reduce the melting and splashing of steel. As a result, the ablation severity of uncoated sheet is severer than that of coated sheet.展开更多
高原地区雷害频繁,电气外绝缘性能降低。修建高原铁路隧道需要对隧道净空绝缘间隙进行修正,其中隧道-架空接触网气隙间距是确定隧道净空间隙的重要依据,雷电冲击放电电压是确定该气隙最小间距的控制因素。国内外现有高海拔修正系列标准...高原地区雷害频繁,电气外绝缘性能降低。修建高原铁路隧道需要对隧道净空绝缘间隙进行修正,其中隧道-架空接触网气隙间距是确定隧道净空间隙的重要依据,雷电冲击放电电压是确定该气隙最小间距的控制因素。国内外现有高海拔修正系列标准均不适用于3000 m以上地区,考虑放电基本特性和原理,在人工气候实验室搭建铁路隧道的典型结构,并模拟高原地区气候特点,研究300~700 mm 5个短间隙在243~4000 m 5个海拔条件下的正、负极性雷电冲击放电特性。基于大气实际参数提出了3种隧道净空绝缘间隙修正方法,建议在2、3、4 km海拔处分别按照340、390、440 mm进行隧道-架空接触网绝缘间隙修正,从而确定最小隧道净空高度。该方法可为高海拔地区铁路的电气化设计和改造提供指导,具有工程应用意义。展开更多
基金supported by the Beijing Science Fund for Distinguished Young Scholars(No.JQ22009)National Natural Science Foundation of China(No.51977198)。
文摘Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.
基金supported by National Natural Science Foundation of China (No. 51337006)
文摘This paper has researched the insulation characteristics of 10% c-C4F8/N2/CO2 mixtures under lightning impulse voltage by experiment. It is shown that the positive and negative lightning impulse breakdown voltages of 10%c-C4F8/N2/CO2 gas mixtures rise linearly as the electrode gap distance and gas pressure increase and under the same conditions, the positive lightning impulse breakdown voltage of the gas mixtures is always higher than the negative lightning impulse breakdown voltage. As the gas mixtures have a little higher liquefied temperature than SF6 and the comprehensive GWP is about 5% of SF6, and the positive and negative lightning impulse breakdown voltages can both reach 60% of SF6, 10%c-C4F8/N2/CO2 gas mixtures can be applied as insulation gas in electrical equipment such as C-GIS, GIT, GIL and so on.
文摘Transient over voltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus,like circuit breakers,transformers,insulators etc.Therefore it is necessary for the GIS also to withstand such voltages without breakdown of Insulation.The system has to be tested under these conditions.Usually the GIS system operates on power frequency.Lightning Impulse Voltage of 1050 kV and Switching Impulse Voltage of 750 kV superimposed on Power frequency voltages of 75 kV,100 kV and 132 kV are applied to Single Phase Gas Insulated Busduct and the maximum movement of Aluminum,Copper and Silver particles is determined.The movement patterns are also determined with and without Monte Carlo Simulation for movement of particle in axial and radial directions.The results show that there is a sudden jump in the movement at the application of impulse on sine wave.This is because of high magnitude voltage of 1050 kV during 1.2/50 μs.Similar movement patterns of reduced maximum movement is observed for Switching Impulse superimposed on sine wave.The results are presented and analyzed.
文摘Looking at the problem of electrical discharge development in mineral oil, it is easy to see that most studies in this area focused on the setups of bare high voltage electrodes having a point-plane electrode arrangement. The setups with insulated electrodes are the mar- gin of these studies but it seems to be important to find the dependences between the paper insulation on high voltage electrode and parameters of the discharges initiated in the vicinity of this electrode. Hence, in this paper the results of researches intended to reveal the role of insulation wrapping on a HV electrode in the mechanism of electrical discharges in transformer oil under lightning impulse of both polar- ities are presented. This role is determined by analysis of the parameters characterizing the discharges (onset voltage, propagation velocity, time to initiation, rise-time of light impulses) and also by observation of their spatio-temporal development and oscillograms of the light emitted by their channels. The research was performed for two model electrode configurations: an electrode with paper insulation and a bare electrode which had the same outer dimensions as the insulated one. The most essential conclusion from performed experiment is related to times to initiation. These times, equal in the case of insulated electrodes and model bare electrode, indicate that the source of "weak points" of the paper-oil insulation system is the oil, not the surface of insulation wrapping or the metal.
基金National Key R&D Program of China(2018YFC1506603)The Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0105)。
文摘The Lightning Mapping Imager(LMI)equipped on the FY-4 A(Feng Yun-4 A)geostationary satellite achieves lightning positioning through optical imaging and has the advantages of high temporal resolution,high stability,and continuous observation.In this study,FY-4 A LMI lightning event,group and flash data from April to August 2018 are selected,and their quality are assessed through qualitative and quantitative comparison with the ground-based Advanced Time of Arrival and Direction system(ADTD)lightning observation network data and the American International Space Station(ISS)lightning imaging sensor(LIS)data.The results show that the spatial distributions of FY-4 A lightning are consistent with those of the ground-based ADTD and ISS LIS.The temporal variation in FY-4 A lightning group frequency is consistent with that of ADTD stroke,which reflects that FY-4 A LMI can capture the lightning occurrence in inland China.Quantitative statistics show that the consistency rate of FY-4 A LMI and ISS LIS events is relatively high but their consistency rate is lower in terms of lightning group and flash data.Compared with the lightning observations by the ISS LIS and the ground-based ADTD,FY-4 A LMI reports fewer lightning events in the Tibetan Plateau.The application of Tibetan Plateau lightning data requires further processing and consideration.
文摘When the tower overhead is struck by the lightning impulse, the lightning current flows into the earth through the impedance of tower and the grounding resistance, which heightens potential of the tower overhead and possibly induces insulator flashover. Lighting rod arrester is used to shield the tower and provide another routine for lightning current, decreasing the potential of tower overhead. In this paper, the performance of a 500 kV lighting rod arrester is tested used in AC transmission system under the current impulse. Besides, the influence of the lightning rod arrester performance on the top potential of tower is also studied. The results show that, when the rod arrester is connected to the tower, the top potential of tower can be obviously limited under the lightning strike.
文摘This paper analyzes the effects of the voltage across insulator of 69 kV and 24 kV lines installed on the same pole. The case studies illustrated the lightning strike to direct top pole and mid span of ground wire using the ATP-EMTP （Alternative Transient Program-Electromagnetic Transient Program）. The results found that when lightning strike the voltage across the 69 kV line insulator at mid span is 1.55 times and 1.34 times higher than at top pole when the front time is 0.25/100μs and 10/350 μs, respectively. When lightning strike the voltage across the 24 kV line at mid span is 1.04 times and 0.64 times higher than at top pole when the front time is 0.25/100μs and 10/350μs, respectively. So the effect of lightning strike is more severe at mid span than at the direct top pole, especially for the 69 kV insulator.
基金supported by National Natural Science Foundation of China (No. 51577117)
文摘The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteristics of steel and investigating the impact of anti-corrosion coating on these characteristics. Ablation characteristics were investigated through the macroscopic morphology and x-ray diffraction patterns on the surface of damaged zones, the microstructure and micro Vickers hardness on the cross-section of damaged zones, and the maximum rear-face temperature of sample sheets. It can be concluded that the ablation areas of uncoated sheet consist of the melted layer and the heat-affect layer. These ablation areas include not only the area ablated directly by the arc root, of which the depth is deeper, but also the area forming due to the splashing of molten steel, of which the depth is shallower and decreases when the area’s distance from the arc attachment point increases. For coated sheet, coating materials have decomposed and evaporated forming an ablation pit on the sheet surface, in which the steel surface is exposed, and zinc filler of coating primer has infused into the exposed surface. The ablation diameter of uncoated sheet relates to the amplitude of the 30/80 μs impulse current in quadratic function, while for coated sheet, the relation is linear. In general, under the 30/80 μs impulse current, the coating can decrease the energy injected from the arc to the steel sheet and reduce the melting and splashing of steel. As a result, the ablation severity of uncoated sheet is severer than that of coated sheet.
文摘高原地区雷害频繁,电气外绝缘性能降低。修建高原铁路隧道需要对隧道净空绝缘间隙进行修正,其中隧道-架空接触网气隙间距是确定隧道净空间隙的重要依据,雷电冲击放电电压是确定该气隙最小间距的控制因素。国内外现有高海拔修正系列标准均不适用于3000 m以上地区,考虑放电基本特性和原理,在人工气候实验室搭建铁路隧道的典型结构,并模拟高原地区气候特点,研究300~700 mm 5个短间隙在243~4000 m 5个海拔条件下的正、负极性雷电冲击放电特性。基于大气实际参数提出了3种隧道净空绝缘间隙修正方法,建议在2、3、4 km海拔处分别按照340、390、440 mm进行隧道-架空接触网绝缘间隙修正,从而确定最小隧道净空高度。该方法可为高海拔地区铁路的电气化设计和改造提供指导,具有工程应用意义。
