The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-po...The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-porcelain insulator is designed.A multi-physics coupling simulation model is built based on numerical simulation methods of the electromagnetic field theory and computational fluid dynamics.Taking average electric field intensity on the surface of the insulator as the characteristic parameter of the electric field distortion degree and the snow crystal collision coefficient and distribution coefficient as the characteristic parameter of snow crystal deposition,the characteristics of snow crystal deposition under different wind speeds and wind direction angles and the electric field characteristics under two snow cover types are analyzed.The simulation results show that the average electric field intensity of composite-porcelain insulators is 10.4%and 13.8%,respectively,lower than that of porcelain insulators in vertical and horizontal wind snow covers,which can effectively reduce the degree of electric field distortion.The collision coefficient of snow crystals on the surface of the composite-porcelain insulator sheds is 16.0%higher than that of the porcelain insulator,and the collision coefficient of the trunk and the fittings are lower 20.2%and 11.9%than that of the porcelain insulator.There is almost no change in the distribution coefficient of the insulator sheds.展开更多
An 800 kV electric power substation can have more than one hundred of porcelain multicone type insulators supporting busbar structures.Two or more sections in series,having middle and end fittings,compose these insula...An 800 kV electric power substation can have more than one hundred of porcelain multicone type insulators supporting busbar structures.Two or more sections in series,having middle and end fittings,compose these insulators.Ageing process can cause degradation of the cement used in this type of insulator and this fact can affect its dielectric performance under heavy rain.This paper presents results of an investigation based on power frequency high voltage tests performed on 800 kV porcelain multicone type insulators,removed from service after having operated for more than 20 years,as well a non-used one that had been stored on site for long time.The insulators were tested in different arrangements:each section at a time and the two sections assembled in series,as actually used insulator columns.The tests were carried out under artificial rain ranging from 1 mm/min to 5 mm/min.The results have confirmed a reduction of up to 30% in the insulator power frequency flashover voltage under 5 mm/min rain conditions and gave important information to the utility about radial cracks that were observed in many insulators and about the discharge mechanisms along the insulators under rain.展开更多
In this paper the relatienship between mi-crostructwtie and strength of alnminiiim-totighed porcelain insu-lator has been investigated .the microstructural characteristic of the porcelain insulator has been put forwar...In this paper the relatienship between mi-crostructwtie and strength of alnminiiim-totighed porcelain insu-lator has been investigated .the microstructural characteristic of the porcelain insulator has been put forward. The results shoiu that the main factors that lead to the strength decreasement of aluminium toughened porcelain insulator are pore, fracture,' coarse alumina grain, aluminium agglomerate and bearing fer-ric matter. The technological factors have also been analysed and appropriate measures have been taken.展开更多
In recent years,more than 50%of the cities in the inland area of our country have suffered from moderate pollution.It can affect the distribution of electric field along the surface of insulator and the pollution char...In recent years,more than 50%of the cities in the inland area of our country have suffered from moderate pollution.It can affect the distribution of electric field along the surface of insulator and the pollution characteristics of its surface area,even endanger the safe operation of transmission lines.This paper takes the XSP-160 porcelain three umbrella insulator under the action of 0–±30 kV DC voltage as the research object,and establishes the physical model of the insulator;uses COMSOL software to simulate the electric field of the insulator.The comparison with the results of the wind tunnel test of North China Electric Power University verifies the rationality of the simulation method.In view of the medium pollution environment which often occurs in the inland area,the force of the polluted particles deposited on the insulator under 110 kV DC voltage was analyzed.The distribution characteristics of the electric field along the surface in the clean and three kinds of pollution environment(light,medium and heavy)were simulated and compared.The results showed that:1)In the moderate pollution environment,the influence of fluid drag force on the movement of polluted particles is greater at the initial stage(0.28–0.33 s);at the late stage(after 0.33 s),the influence of the electric field force begins to increase,and gradually plays a major role in the process of fouling.2)In the three different polluted environments,the potential along the surface of each umbrella skirt of the insulator increases non-linearly with the increasing of the pollution concentration,and there are apparent potential inflection points near b and l.3)The pollution particle concentration has the most obvious influence on the electric field along the low-voltage umbrella skirt,whose potential distortion rate can be up to 220 times in the heavy polluted environment.展开更多
Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porc...Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porcelain insulator sheds affected by dynamic deformation of pendant water drops and effects of the dimensionless number of fluids,the Weber number(We)and the electric Bond number(BoE),on it for influencing factors'analysis.Flow‐electric field coupling simulations were carried out to compute the magnitude and the position of AC electric fields between the sheds.The results show that the maximum electric field at a point in time(Etmax)increases significantly after the breakup of the pendant water drop,and its position alters accordingly.For low We and BoE,the global maximum electric field(Egmax)increases with increasing We and BoE,respectively.It is much closer to the adjacent sheds and occurs later than Etmax at the breakup of the pendant water drop(Ebmax).By contrast,Egmax decreases in different degrees at high We and BoE,respectively.There is little difference between Egmax and Ebmax in the position and the occurring time.The influence mechanism on the maximum electric field and discharges and the relationship between discharges induced by the pendant water drop and rain flashover are discussed.展开更多
基金National Natural Science Foundation of China(No.51867013)。
文摘The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-porcelain insulator is designed.A multi-physics coupling simulation model is built based on numerical simulation methods of the electromagnetic field theory and computational fluid dynamics.Taking average electric field intensity on the surface of the insulator as the characteristic parameter of the electric field distortion degree and the snow crystal collision coefficient and distribution coefficient as the characteristic parameter of snow crystal deposition,the characteristics of snow crystal deposition under different wind speeds and wind direction angles and the electric field characteristics under two snow cover types are analyzed.The simulation results show that the average electric field intensity of composite-porcelain insulators is 10.4%and 13.8%,respectively,lower than that of porcelain insulators in vertical and horizontal wind snow covers,which can effectively reduce the degree of electric field distortion.The collision coefficient of snow crystals on the surface of the composite-porcelain insulator sheds is 16.0%higher than that of the porcelain insulator,and the collision coefficient of the trunk and the fittings are lower 20.2%and 11.9%than that of the porcelain insulator.There is almost no change in the distribution coefficient of the insulator sheds.
文摘An 800 kV electric power substation can have more than one hundred of porcelain multicone type insulators supporting busbar structures.Two or more sections in series,having middle and end fittings,compose these insulators.Ageing process can cause degradation of the cement used in this type of insulator and this fact can affect its dielectric performance under heavy rain.This paper presents results of an investigation based on power frequency high voltage tests performed on 800 kV porcelain multicone type insulators,removed from service after having operated for more than 20 years,as well a non-used one that had been stored on site for long time.The insulators were tested in different arrangements:each section at a time and the two sections assembled in series,as actually used insulator columns.The tests were carried out under artificial rain ranging from 1 mm/min to 5 mm/min.The results have confirmed a reduction of up to 30% in the insulator power frequency flashover voltage under 5 mm/min rain conditions and gave important information to the utility about radial cracks that were observed in many insulators and about the discharge mechanisms along the insulators under rain.
文摘In this paper the relatienship between mi-crostructwtie and strength of alnminiiim-totighed porcelain insu-lator has been investigated .the microstructural characteristic of the porcelain insulator has been put forward. The results shoiu that the main factors that lead to the strength decreasement of aluminium toughened porcelain insulator are pore, fracture,' coarse alumina grain, aluminium agglomerate and bearing fer-ric matter. The technological factors have also been analysed and appropriate measures have been taken.
基金Science and Technology Project of State Grid Corporation(GY7111053)[www.sgcc.com.cn].
文摘In recent years,more than 50%of the cities in the inland area of our country have suffered from moderate pollution.It can affect the distribution of electric field along the surface of insulator and the pollution characteristics of its surface area,even endanger the safe operation of transmission lines.This paper takes the XSP-160 porcelain three umbrella insulator under the action of 0–±30 kV DC voltage as the research object,and establishes the physical model of the insulator;uses COMSOL software to simulate the electric field of the insulator.The comparison with the results of the wind tunnel test of North China Electric Power University verifies the rationality of the simulation method.In view of the medium pollution environment which often occurs in the inland area,the force of the polluted particles deposited on the insulator under 110 kV DC voltage was analyzed.The distribution characteristics of the electric field along the surface in the clean and three kinds of pollution environment(light,medium and heavy)were simulated and compared.The results showed that:1)In the moderate pollution environment,the influence of fluid drag force on the movement of polluted particles is greater at the initial stage(0.28–0.33 s);at the late stage(after 0.33 s),the influence of the electric field force begins to increase,and gradually plays a major role in the process of fouling.2)In the three different polluted environments,the potential along the surface of each umbrella skirt of the insulator increases non-linearly with the increasing of the pollution concentration,and there are apparent potential inflection points near b and l.3)The pollution particle concentration has the most obvious influence on the electric field along the low-voltage umbrella skirt,whose potential distortion rate can be up to 220 times in the heavy polluted environment.
基金supported by the National Natural Science Foundation of China under Grant No.52077084.
文摘Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porcelain insulator sheds affected by dynamic deformation of pendant water drops and effects of the dimensionless number of fluids,the Weber number(We)and the electric Bond number(BoE),on it for influencing factors'analysis.Flow‐electric field coupling simulations were carried out to compute the magnitude and the position of AC electric fields between the sheds.The results show that the maximum electric field at a point in time(Etmax)increases significantly after the breakup of the pendant water drop,and its position alters accordingly.For low We and BoE,the global maximum electric field(Egmax)increases with increasing We and BoE,respectively.It is much closer to the adjacent sheds and occurs later than Etmax at the breakup of the pendant water drop(Ebmax).By contrast,Egmax decreases in different degrees at high We and BoE,respectively.There is little difference between Egmax and Ebmax in the position and the occurring time.The influence mechanism on the maximum electric field and discharges and the relationship between discharges induced by the pendant water drop and rain flashover are discussed.
