It is one of the most effective ways to use laboratory long air gap discharges for investigating the fundamental process involved in the lightning strike.During the 1960s and the 1970s,the electro-geometrical method(E...It is one of the most effective ways to use laboratory long air gap discharges for investigating the fundamental process involved in the lightning strike.During the 1960s and the 1970s,the electro-geometrical method(EGM)and the rolling sphere method were developed base on the breakdowncharacteristics of negative long spark discharges,which have been widely used to design the lightning shielding system of transmission lines and structures.In recent years,the scale of the power facilities is increased dramatically with the rising of power grid's voltage level.The impact of upward connecting leader launched from those large-scale facilities on the lightning shielding performance cannot be neglected;otherwise,the validity of the EGM in the lightning shielding design of EHV and UHV transmission lines will be challenged.The research evolutions on the lightning striking distance,the lightning simulation experiments and the positive upward connecting leader process by using laboratory long sparks are reviewed and discussed in this paper.展开更多
In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave th...In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.展开更多
A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester ...A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.展开更多
In the paper,the statistical modeling method of the lightning attachment process to extended objects has been proposed.The modeling takes into account the probabilities of lightning occurrence with current of differen...In the paper,the statistical modeling method of the lightning attachment process to extended objects has been proposed.The modeling takes into account the probabilities of lightning occurrence with current of different amplitudes, and nonlinear variation of spark resistance at leader channel growth.The method also takes into consideration the dependency of velocity and acceleration of a lightning leader on its potential.The propagation of lightning channel towards the earth is tortuous and random in orientation and does not depend upon ground objects until it enters into"last stroke zone".It assumes that the lightning leader channel orientation begins when its streamer zone touches the earth,a grounded object,a grounded lightning rod or a streamer zone of the ascending leader.The probable frequency of lightning strikes to an investigated object can be obtained by the summation of the total probable number of strikes of all possible potentials at each node of the object,appearing with the assigned probability,as well as the points of origin of the heads of lightning leaders from all nodes on the plain(over the object) at corresponding heights.The proposed method is implemented to calculate the lightning stroke probability to a high voltage substation. Due to lightning attraction from the territory greater than that of the investigated object,the total number of annual probable lightning strokes to the object is increased by 1.28 times in comparison with the case of the same flat territory.展开更多
This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system ...This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system was developed,in which high-frequency distributed parameters of the blade conducts,tower,power cables and stator windings of generator were calculated based on finite element method,and the models of converter,grounding,loads, surge protection devices and power grid were established.The voltage distribution along stator windings,when struck by lightning with 10/350μs wave form and different amplitude current between 50 kA and 200 kA,was simulated using electro-magnetic transient analysis method.The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings,and the voltage distribution along the windings is nonuniform initially.The voltage drops of each coil fall from first to last coil,and the highest voltage drop appears on the first coil.The insulation damage may occur on the windings under lightning overvoltage.The surge arresters can restrain the lightning surge in effect and protect the insulation.The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator,but is only 2.7 kV with arresters.展开更多
This paper presents an investigation on the attractive width of high voltage transmission lines to lightning strikes.In order to design the optimal lightning protection,the estimated number of lightning flashes on the...This paper presents an investigation on the attractive width of high voltage transmission lines to lightning strikes.In order to design the optimal lightning protection,the estimated number of lightning flashes on the line, which is based on its attractive width,needs to be determined.The investigation was performed using experiments with model tests at the Mississippi State University High Voltage Laboratory.For laboratory experiments,a total of 2,100 negative and positive switching impulse voltages were applied to transmission line models from a conducting rod,which represented a lightning downward leader.Different tested models of transmission lines on a scale of 1:100 were used.The effects of overhead ground wires,phase conductors,tower structures,and the magnitude and polarity of lightning strokes were also studied.The attractive width increased gradually with the height of overhead ground wires and towers as well as the magnitude of the lightning stroke current.Impulse polarity had an impact on the attractive width,and the attractive width for negative polarity was larger than that for positive polarity.The taller tower had more effect on flash distribution to transmission lines than the shorter one.The experimental results agree with the actual transmission line observations published in literature.The new expressions for the attractive width of transmission lines,based on the experimental results,were established.The accurate estimation of the attractive width can help electric power utilities plan transmission systems reliably and economically.The detailed description of the background problem,proposed method,experimental results,and analysis are presented in this paper.展开更多
The increase of voltage level for AC and DC transmission systems requires some changes in the high voltage testing for Ultra High Voltage(UHV) equipment.After a short description of the coordination work in the standa...The increase of voltage level for AC and DC transmission systems requires some changes in the high voltage testing for Ultra High Voltage(UHV) equipment.After a short description of the coordination work in the standardization bodies the requirements for UHV equipment are mentioned.The main points concerning high voltage testing of UHV equipment are the impulse shape of standard lightning impulse voltage,the evaluation of the test voltage for impulses with oscillations or overshoot near the peak and the time parameter of switching impulses.The linearity check of the measuring devices,the proximity effect,the wet tests and the atmospheric correction factors are further points to be discussed concerning testing of UHV equipment.展开更多
Nepcon China 2006展览会上，环球仪器公司展出了两个组装生产线实例：一个采用Genesis平台，另一个采用Advantis平台，每条线都向人们展示了针对特定应用和生产目标的平台方案所具有的独特优势。此外，展台上还专门展示了环球仪器公司...Nepcon China 2006展览会上，环球仪器公司展出了两个组装生产线实例：一个采用Genesis平台，另一个采用Advantis平台，每条线都向人们展示了针对特定应用和生产目标的平台方案所具有的独特优势。此外，展台上还专门展示了环球仪器公司的Lightning闪电贴装头，并举办了一系列PoP（堆叠封装）技术的免费讲座。展开更多
文摘It is one of the most effective ways to use laboratory long air gap discharges for investigating the fundamental process involved in the lightning strike.During the 1960s and the 1970s,the electro-geometrical method(EGM)and the rolling sphere method were developed base on the breakdowncharacteristics of negative long spark discharges,which have been widely used to design the lightning shielding system of transmission lines and structures.In recent years,the scale of the power facilities is increased dramatically with the rising of power grid's voltage level.The impact of upward connecting leader launched from those large-scale facilities on the lightning shielding performance cannot be neglected;otherwise,the validity of the EGM in the lightning shielding design of EHV and UHV transmission lines will be challenged.The research evolutions on the lightning striking distance,the lightning simulation experiments and the positive upward connecting leader process by using laboratory long sparks are reviewed and discussed in this paper.
文摘In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.
基金Project supported by China Postdoctoral Science Foundation （ 10000072311030 ）, Scienee technology Research Foundation of Shandong University of China {10000080398125）.
文摘A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.
文摘In the paper,the statistical modeling method of the lightning attachment process to extended objects has been proposed.The modeling takes into account the probabilities of lightning occurrence with current of different amplitudes, and nonlinear variation of spark resistance at leader channel growth.The method also takes into consideration the dependency of velocity and acceleration of a lightning leader on its potential.The propagation of lightning channel towards the earth is tortuous and random in orientation and does not depend upon ground objects until it enters into"last stroke zone".It assumes that the lightning leader channel orientation begins when its streamer zone touches the earth,a grounded object,a grounded lightning rod or a streamer zone of the ascending leader.The probable frequency of lightning strikes to an investigated object can be obtained by the summation of the total probable number of strikes of all possible potentials at each node of the object,appearing with the assigned probability,as well as the points of origin of the heads of lightning leaders from all nodes on the plain(over the object) at corresponding heights.The proposed method is implemented to calculate the lightning stroke probability to a high voltage substation. Due to lightning attraction from the territory greater than that of the investigated object,the total number of annual probable lightning strokes to the object is increased by 1.28 times in comparison with the case of the same flat territory.
基金Supported by National Natural Science Foundation of China(50877063)
文摘This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system was developed,in which high-frequency distributed parameters of the blade conducts,tower,power cables and stator windings of generator were calculated based on finite element method,and the models of converter,grounding,loads, surge protection devices and power grid were established.The voltage distribution along stator windings,when struck by lightning with 10/350μs wave form and different amplitude current between 50 kA and 200 kA,was simulated using electro-magnetic transient analysis method.The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings,and the voltage distribution along the windings is nonuniform initially.The voltage drops of each coil fall from first to last coil,and the highest voltage drop appears on the first coil.The insulation damage may occur on the windings under lightning overvoltage.The surge arresters can restrain the lightning surge in effect and protect the insulation.The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator,but is only 2.7 kV with arresters.
文摘This paper presents an investigation on the attractive width of high voltage transmission lines to lightning strikes.In order to design the optimal lightning protection,the estimated number of lightning flashes on the line, which is based on its attractive width,needs to be determined.The investigation was performed using experiments with model tests at the Mississippi State University High Voltage Laboratory.For laboratory experiments,a total of 2,100 negative and positive switching impulse voltages were applied to transmission line models from a conducting rod,which represented a lightning downward leader.Different tested models of transmission lines on a scale of 1:100 were used.The effects of overhead ground wires,phase conductors,tower structures,and the magnitude and polarity of lightning strokes were also studied.The attractive width increased gradually with the height of overhead ground wires and towers as well as the magnitude of the lightning stroke current.Impulse polarity had an impact on the attractive width,and the attractive width for negative polarity was larger than that for positive polarity.The taller tower had more effect on flash distribution to transmission lines than the shorter one.The experimental results agree with the actual transmission line observations published in literature.The new expressions for the attractive width of transmission lines,based on the experimental results,were established.The accurate estimation of the attractive width can help electric power utilities plan transmission systems reliably and economically.The detailed description of the background problem,proposed method,experimental results,and analysis are presented in this paper.
文摘The increase of voltage level for AC and DC transmission systems requires some changes in the high voltage testing for Ultra High Voltage(UHV) equipment.After a short description of the coordination work in the standardization bodies the requirements for UHV equipment are mentioned.The main points concerning high voltage testing of UHV equipment are the impulse shape of standard lightning impulse voltage,the evaluation of the test voltage for impulses with oscillations or overshoot near the peak and the time parameter of switching impulses.The linearity check of the measuring devices,the proximity effect,the wet tests and the atmospheric correction factors are further points to be discussed concerning testing of UHV equipment.
文摘Nepcon China 2006展览会上，环球仪器公司展出了两个组装生产线实例：一个采用Genesis平台，另一个采用Advantis平台，每条线都向人们展示了针对特定应用和生产目标的平台方案所具有的独特优势。此外，展台上还专门展示了环球仪器公司的Lightning闪电贴装头，并举办了一系列PoP（堆叠封装）技术的免费讲座。
