The nanosecond(ns) pulsed nitrogen dielectric barrier discharge(DBD) is employed to enhance the hydrophilicity of polypropylene(PP) surface and improve its application effect.The discharge characteristics of the ns pu...The nanosecond(ns) pulsed nitrogen dielectric barrier discharge(DBD) is employed to enhance the hydrophilicity of polypropylene(PP) surface and improve its application effect.The discharge characteristics of the ns pulsed nitrogen DBD with different pulse rise times(from 50to 500 ns) are investigated by electrical and optical diagnostic methods and the discharge uniformity is quantitatively analyzed by image processing method.To characterize the surface hydrophilicity,the water contact angle(WCA) is measured,and the physical morphology and chemical composition of PP before and after modification are analyzed to explore the effect of plasma on PP surface.It is found that with increasing pulse rise time from 50 to 500 ns,DBD uniformity becomes worse,energy efficiency decreases from 20% to 10.8%,and electron density decrease from 6.6 × 10^(11)to 5.5 × 10^(11)cm^(-3).The tendency of electron temperature is characterized with the intensity ratio of N_(2)/N_(2)^(+)emission spectrum,which decreases from 17.4 to15.9 indicating the decreasing of T_(e) with increasing pulse rise time from 50 to 500 ns.The PP surface treated with 50 ns pulse rise time DBD has a lower WCA(~47°),while the WCA of PP treated with 100 to 500 ns pulse rise time DBD expands gradually(~50°–57°).According to the study of the fixed-point WCA values,the DBD-treated PP surface has superior uniformity under50 ns pulse rise time(3° variation) than under 300 ns pulse rise time(8° variation).After DBD treatment,the increased surface roughness from 2.0 to 9.8 nm and hydrophilic oxygencontaining groups on the surface,i.e.hydroxyl(-OH) and carbonyl(C=O) have played the significant role to improve the sample’s surface hydrophilicity.The short pulse voltage rise time enhances the reduced electric field strength(E/n) in the discharge space and improves the discharge uniformity,which makes relatively sufficient physical and chemical reactions have taken place on the PP surface,resulting in better treatment uniformity.展开更多
The focus of this paper is to provide a comprehensive review of various insulation performance improvement methods for vacuum-solid and compressed air-solid interfaces.The surface characteristics of insulating materia...The focus of this paper is to provide a comprehensive review of various insulation performance improvement methods for vacuum-solid and compressed air-solid interfaces.The surface characteristics of insulating materials have a significant impact on the flashover voltage along the surface.These surface characteristics include the surface resistivity,surface charge behavior,roughness,secondary electron emission coefficient,and intrinsic properties of the material.Numerous challenges remain to be explored and resolved concerning the causes and mechanisms of surface flashover,methods to increase flashover voltage,and their underlying physical principles.Therefore,the flashover phenomenon along the insulation surface and methods of increasing the flashover voltage have become challenging research key topics in related fields.展开更多
The 2050 carbon-neutral vision spawns a novel energy structure revolution,and the construction of the future energy structure is based on equipment innovation.Insulating material,as the core of electrical power equipm...The 2050 carbon-neutral vision spawns a novel energy structure revolution,and the construction of the future energy structure is based on equipment innovation.Insulating material,as the core of electrical power equipment and electrified transportation asset,faces unprecedented challenges and opportunities.The goal of carbon neutral and the urgent need for innovation in electric power equipment and electrification assets are first discussed.The engineering challenges constrained by the insulation system in future electric power equipment/devices and electrified transportation assets are investigated.Insulating materials,including intelligent insulating material,high thermal conductivity insulating material,high energy storage density insulating material,extreme environment resistant insulating material,and environmental-friendly insulating material,are cat-egorised with their scientific issues,opportunities and challenges under the goal of carbon neutrality being discussed.In the context of carbon neutrality,not only improves the understanding of the insulation problems from a macro level,that is,electrical power equipment and electrified transportation asset,but also offers opportunities,remaining issues and challenges from the insulating material level.It is hoped that this paper en-visions the challenges regarding design and reliability of insulations in electrical equipment and electric vehicles in the context of policies towards carbon neutrality rules.The authors also hope that this paper can be helpful in future development and research of novel insulating materials,which promote the realisation of the carbon-neutral vision.展开更多
The urgent need for power transmission is the reason for leading research on the safer operation of high‐voltage cables.These high‐voltage cables are emerging as an efficient technology for underground power transmi...The urgent need for power transmission is the reason for leading research on the safer operation of high‐voltage cables.These high‐voltage cables are emerging as an efficient technology for underground power transmission.However,the electrochemical corrosion of aluminium(Al)metal sheaths in these cables is a common and challenging degradation process.Herein,the corrosion mechanisms and electrochemical analysis are investigated by using scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),electrochemical impedance spectroscopy(EIS)and laboratory‐designed electro-chemical characterisation techniques.In the corrosion experiments,the authors evaluated the corrosion rate by measuring the release rate of hydrogen gas and explored the different roles of sodium polyacrylate(NaPA)during the corrosion process.It is found that the complexation reactions between NaPA and Al inhibited corrosion while increased the resistance of the buffer layer.The proposed mechanisms of corrosion in this study can improve the lifespan and sustainability of high‐voltage power transmission.展开更多
The flashover strength of epoxy(EP)insulations in the High voltage direct current applications of future energy grids can be improved by tailoring their surface condition.This work aims to improve the DC surface flash...The flashover strength of epoxy(EP)insulations in the High voltage direct current applications of future energy grids can be improved by tailoring their surface condition.This work aims to improve the DC surface flashover characteristics of EP after being treated with sandpaper of different gradings.Samples with virgin EP and homogenously modified EP considering varying surface roughness(R_(a)=0.54,3.16,5.24,and 8.35μm)are prepared.Different experimental characterisations,such as water contact angle,surface intrinsic conductivity,surface voltages,flashover strength,and trap distributions are conducted and evaluated to analyse the difference between virgin and treated EP.Moreover,based on the obtained experimental results of homogenously treated EP and theoretical analysis,the concept of surface functionally graded materials(SFGMs)is put forward.The flashover voltages of homogenously treated EP are augmented significantly compared to virgin EP regardless of the voltage polarity and enhanced by enhancing the surface roughness.The sample T_(Model‐C) with SFGM design shows a 45.02%and 43.75%improvement in the negative and positive flashover voltages than that of the virgin EP.In the end,COMSOL simulations are conducted to justify the experimental findings and to analyse the difference between virgin and modified samples in terms of electric field distribution.展开更多
This paper analyses the impact of square wave pulse voltage deadtime on the partial discharge(PD)and the lifetime of turn-to-turn insulation.A bipolar repetitive pulse voltage with a deadtime of 0–10μs is produced u...This paper analyses the impact of square wave pulse voltage deadtime on the partial discharge(PD)and the lifetime of turn-to-turn insulation.A bipolar repetitive pulse voltage with a deadtime of 0–10μs is produced using double half-bridge solid-state switches having push–pull technology controlled by a field-programmable gate array.The mechanism of the discharge process at rising and falling edges of the pulse voltage before and after deadtime is analysed in detail.The discharge amplitude and PD probability at the rising/falling edges of the voltage waveform increase as the deadtime increases from 0 to 10μs due to the remanent charges.The number of PD and their intensity is higher at the first rising/falling edges of pulse voltage as compared to the second rising/falling edges for all deadtimes 0–10μs.As the deadtime increases beyond 2μs,the number of PDs increases and concentrates at a specific phase angle of rising/falling edges.These localise discharges degrade the insulation material and reduce its lifetime.This study helps to identify the inverter-fed motor insulation faults due to deadtime.It can provide guidelines to motor insulation designers to determine the limit value of deadtime to compensate PD and ensure the safer operation of such motors.展开更多
Variation in air pressure severely affects the insulation of electric vehicle(EV)motors,hence weakening the reliability of EVs for safe operation.Nomex‐polyimide‐Nomex,a typical insulation material for EV motors,was...Variation in air pressure severely affects the insulation of electric vehicle(EV)motors,hence weakening the reliability of EVs for safe operation.Nomex‐polyimide‐Nomex,a typical insulation material for EV motors,was used to investigate the motor insulation performance under different air pressures.The results show that the partial discharge inception voltage is significantly reduced for EV motors operated at lower air pressures,and the probability of partial discharge(PD)occurrence is increased.The macroscopic results reveal that the active area of the PD expands at low pressure,while the non‐corroded ring appears in the centre.Additionally,although the number and amplitude of the PD increase significantly with decrease in air pressure,the active area of the PD expands and electrical stress on the insulation per unit area increases slowly.Therefore,when the pressure decreased from 60 to 40 kPa,the endurance life does not show a significant downward trend.Furthermore,the dielectric constant and loss of the low‐pressure samples significantly change during the ageing process,which further indicates critical degradation of the insulation.The aforementioned investigations reveal that the air pressure at different altitudes has a significant impact on the performance of insulation materials.展开更多
The ground wire is significantly interfered by the current above 1μA in the industrial field during the traditional polarisation and depolarisation current(PDC)measurement.This paper explains a method to test PDC fro...The ground wire is significantly interfered by the current above 1μA in the industrial field during the traditional polarisation and depolarisation current(PDC)measurement.This paper explains a method to test PDC from high-voltage wire using a principle of equipotential picoammeter,which is completely isolated from the ground wire and connected in series with the high voltage wire.In this method,a device is designed with a multi-range automatic switching function.The device can automatically switch the test range current from 1 pA to 10 mA with a resolution of 1 pA.To demonstrate the device and effectiveness of this new method,the traditional and the proposed new device are used to test the PDC of cable samples in the laboratory as well as in an industrial environment.It is worth noting that there is almost no interference on the Earth wire in the laboratory environment but massive interference in the industrial environment using a traditional method of PDC measurement from ground or Earth wire.The new method of high-voltage testing can efficiently eliminate the interference and accurately measure PDC in a strong industrial interference environment.Furthermore,the wiring of this new method and device is relatively simple,which is convenient for industrial applications.展开更多
Silicone rubber(SiR)composite material is a modern-day insulator for high voltage outdoor applications.The imperfection attributed to SiR is its weak resistance to tracking and erosion when exposed to an outdoor pollu...Silicone rubber(SiR)composite material is a modern-day insulator for high voltage outdoor applications.The imperfection attributed to SiR is its weak resistance to tracking and erosion when exposed to an outdoor polluted environment which reduces its operational lifetime.This paper investigates the performance of SiR with the addition of 0,1,2.5,5,10 and 20%by weight contents of nano alumina(Al_(2)O_(3)).Inclined plane tests are performed according to IEC 60587 using the step up tracking voltage method with an initial voltage of 3.0 kV and the contaminant solution flow rate is maintained at 0.3 ml/min using a peristaltic pump.The applied voltage level is increased at a rate of 0.25 kV/h.Results suggest that physical tracking,erosion,RMS leakage current and surface partial discharge(PD)performance of samples is improved with the addition of nano alumina.The tracking length,eroded mass,RMS leakage current and average PD magnitude are measured 22%,79%,30%and 52%lesser in 20 wt%relative to 0 wt%,respectively.A thermal distribution analysis is undertaken with infrared camera and it is discovered that heat is accumulated in the discharge area of the liquid flow.The maximum temperature on the insulating specimen is decreased with increasing nanofiller contents.The above promising findings can be due to better thermal stability with low chain mobility at the interaction zone of SiR and alumina.Moreover,less liquid evaporation due to better thermal conduction and improved physical bonding between SiR and nano alumina are possible reasons behind the excellent performance of nanocomposites.展开更多
Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once...Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once ignited,substantially reduce its working life.This paper attempts to investigate tracking/erosion performance of room temperature vulcanized(RTV)silicone rubber along with flame retardant parameters using aluminum trihydrate(ATH),graphene nanosheets(GN)and milled glass fiber(GF)additives.The inclined plane test(IPT)was performed in line with criteria defined in IEC 60587 using step-up tracking voltage method while flame retardancy is evaluated according to ASTM E 1354.0 using a cone calorimeter.Results suggest 30% of ATH assists in improving physical tracking/erosion resistance of pristine silicone elastomer rubber by impeding development of leakage current and a great reduction in maximum average temperatures on the surface of RTV2.Further improvement in performance of RTV2 is achieved through introduction of 1%of GN and 5% of GF as seen in RTV4.Moreover,30% of ATH reduces heat release rate and smoke production rate,and this trend is improved with the introduction of GN/GF.RTV4 has pop up as the most promising silicone rubber composite with excellent electrical tracking,erosion,and flame resistance performance relative to its counterparts in this study.展开更多
基金supported by National Natural Science Foundation of China (Nos. 52037004, 51777091 and52250410350)Postgraduate Research&Practice Innovation Program of Jiangsu Province (No.KYCX22_1314)。
文摘The nanosecond(ns) pulsed nitrogen dielectric barrier discharge(DBD) is employed to enhance the hydrophilicity of polypropylene(PP) surface and improve its application effect.The discharge characteristics of the ns pulsed nitrogen DBD with different pulse rise times(from 50to 500 ns) are investigated by electrical and optical diagnostic methods and the discharge uniformity is quantitatively analyzed by image processing method.To characterize the surface hydrophilicity,the water contact angle(WCA) is measured,and the physical morphology and chemical composition of PP before and after modification are analyzed to explore the effect of plasma on PP surface.It is found that with increasing pulse rise time from 50 to 500 ns,DBD uniformity becomes worse,energy efficiency decreases from 20% to 10.8%,and electron density decrease from 6.6 × 10^(11)to 5.5 × 10^(11)cm^(-3).The tendency of electron temperature is characterized with the intensity ratio of N_(2)/N_(2)^(+)emission spectrum,which decreases from 17.4 to15.9 indicating the decreasing of T_(e) with increasing pulse rise time from 50 to 500 ns.The PP surface treated with 50 ns pulse rise time DBD has a lower WCA(~47°),while the WCA of PP treated with 100 to 500 ns pulse rise time DBD expands gradually(~50°–57°).According to the study of the fixed-point WCA values,the DBD-treated PP surface has superior uniformity under50 ns pulse rise time(3° variation) than under 300 ns pulse rise time(8° variation).After DBD treatment,the increased surface roughness from 2.0 to 9.8 nm and hydrophilic oxygencontaining groups on the surface,i.e.hydroxyl(-OH) and carbonyl(C=O) have played the significant role to improve the sample’s surface hydrophilicity.The short pulse voltage rise time enhances the reduced electric field strength(E/n) in the discharge space and improves the discharge uniformity,which makes relatively sufficient physical and chemical reactions have taken place on the PP surface,resulting in better treatment uniformity.
基金supported by the Fundamental Research Funds for the Central Universities(2024JBMC039)National Natural Science Foundation of China(52377131)Fundamental Research Funds for the Central Universities(E18JB00070,E17JB00020).
文摘The focus of this paper is to provide a comprehensive review of various insulation performance improvement methods for vacuum-solid and compressed air-solid interfaces.The surface characteristics of insulating materials have a significant impact on the flashover voltage along the surface.These surface characteristics include the surface resistivity,surface charge behavior,roughness,secondary electron emission coefficient,and intrinsic properties of the material.Numerous challenges remain to be explored and resolved concerning the causes and mechanisms of surface flashover,methods to increase flashover voltage,and their underlying physical principles.Therefore,the flashover phenomenon along the insulation surface and methods of increasing the flashover voltage have become challenging research key topics in related fields.
文摘The 2050 carbon-neutral vision spawns a novel energy structure revolution,and the construction of the future energy structure is based on equipment innovation.Insulating material,as the core of electrical power equipment and electrified transportation asset,faces unprecedented challenges and opportunities.The goal of carbon neutral and the urgent need for innovation in electric power equipment and electrification assets are first discussed.The engineering challenges constrained by the insulation system in future electric power equipment/devices and electrified transportation assets are investigated.Insulating materials,including intelligent insulating material,high thermal conductivity insulating material,high energy storage density insulating material,extreme environment resistant insulating material,and environmental-friendly insulating material,are cat-egorised with their scientific issues,opportunities and challenges under the goal of carbon neutrality being discussed.In the context of carbon neutrality,not only improves the understanding of the insulation problems from a macro level,that is,electrical power equipment and electrified transportation asset,but also offers opportunities,remaining issues and challenges from the insulating material level.It is hoped that this paper en-visions the challenges regarding design and reliability of insulations in electrical equipment and electric vehicles in the context of policies towards carbon neutrality rules.The authors also hope that this paper can be helpful in future development and research of novel insulating materials,which promote the realisation of the carbon-neutral vision.
文摘The urgent need for power transmission is the reason for leading research on the safer operation of high‐voltage cables.These high‐voltage cables are emerging as an efficient technology for underground power transmission.However,the electrochemical corrosion of aluminium(Al)metal sheaths in these cables is a common and challenging degradation process.Herein,the corrosion mechanisms and electrochemical analysis are investigated by using scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),electrochemical impedance spectroscopy(EIS)and laboratory‐designed electro-chemical characterisation techniques.In the corrosion experiments,the authors evaluated the corrosion rate by measuring the release rate of hydrogen gas and explored the different roles of sodium polyacrylate(NaPA)during the corrosion process.It is found that the complexation reactions between NaPA and Al inhibited corrosion while increased the resistance of the buffer layer.The proposed mechanisms of corrosion in this study can improve the lifespan and sustainability of high‐voltage power transmission.
基金National Natural Science Foundation of China,Grant/Award Number:92166206Fundamental Research Funds for the Central Universities,Grant/Award Number:2022CDJQY‐014111 Project of the Ministry of Education of China,Grant/Award Number:BP0820005。
文摘The flashover strength of epoxy(EP)insulations in the High voltage direct current applications of future energy grids can be improved by tailoring their surface condition.This work aims to improve the DC surface flashover characteristics of EP after being treated with sandpaper of different gradings.Samples with virgin EP and homogenously modified EP considering varying surface roughness(R_(a)=0.54,3.16,5.24,and 8.35μm)are prepared.Different experimental characterisations,such as water contact angle,surface intrinsic conductivity,surface voltages,flashover strength,and trap distributions are conducted and evaluated to analyse the difference between virgin and treated EP.Moreover,based on the obtained experimental results of homogenously treated EP and theoretical analysis,the concept of surface functionally graded materials(SFGMs)is put forward.The flashover voltages of homogenously treated EP are augmented significantly compared to virgin EP regardless of the voltage polarity and enhanced by enhancing the surface roughness.The sample T_(Model‐C) with SFGM design shows a 45.02%and 43.75%improvement in the negative and positive flashover voltages than that of the virgin EP.In the end,COMSOL simulations are conducted to justify the experimental findings and to analyse the difference between virgin and modified samples in terms of electric field distribution.
基金National Natural Science Foundation of China,Grant/Award Number:51977134。
文摘This paper analyses the impact of square wave pulse voltage deadtime on the partial discharge(PD)and the lifetime of turn-to-turn insulation.A bipolar repetitive pulse voltage with a deadtime of 0–10μs is produced using double half-bridge solid-state switches having push–pull technology controlled by a field-programmable gate array.The mechanism of the discharge process at rising and falling edges of the pulse voltage before and after deadtime is analysed in detail.The discharge amplitude and PD probability at the rising/falling edges of the voltage waveform increase as the deadtime increases from 0 to 10μs due to the remanent charges.The number of PD and their intensity is higher at the first rising/falling edges of pulse voltage as compared to the second rising/falling edges for all deadtimes 0–10μs.As the deadtime increases beyond 2μs,the number of PDs increases and concentrates at a specific phase angle of rising/falling edges.These localise discharges degrade the insulation material and reduce its lifetime.This study helps to identify the inverter-fed motor insulation faults due to deadtime.It can provide guidelines to motor insulation designers to determine the limit value of deadtime to compensate PD and ensure the safer operation of such motors.
基金National Natural Science Foundation of China,Grant/Award Numbers:52250410350,51977134。
文摘Variation in air pressure severely affects the insulation of electric vehicle(EV)motors,hence weakening the reliability of EVs for safe operation.Nomex‐polyimide‐Nomex,a typical insulation material for EV motors,was used to investigate the motor insulation performance under different air pressures.The results show that the partial discharge inception voltage is significantly reduced for EV motors operated at lower air pressures,and the probability of partial discharge(PD)occurrence is increased.The macroscopic results reveal that the active area of the PD expands at low pressure,while the non‐corroded ring appears in the centre.Additionally,although the number and amplitude of the PD increase significantly with decrease in air pressure,the active area of the PD expands and electrical stress on the insulation per unit area increases slowly.Therefore,when the pressure decreased from 60 to 40 kPa,the endurance life does not show a significant downward trend.Furthermore,the dielectric constant and loss of the low‐pressure samples significantly change during the ageing process,which further indicates critical degradation of the insulation.The aforementioned investigations reveal that the air pressure at different altitudes has a significant impact on the performance of insulation materials.
基金National Natural Science Foundation of China,Grant/Award Number:51877142。
文摘The ground wire is significantly interfered by the current above 1μA in the industrial field during the traditional polarisation and depolarisation current(PDC)measurement.This paper explains a method to test PDC from high-voltage wire using a principle of equipotential picoammeter,which is completely isolated from the ground wire and connected in series with the high voltage wire.In this method,a device is designed with a multi-range automatic switching function.The device can automatically switch the test range current from 1 pA to 10 mA with a resolution of 1 pA.To demonstrate the device and effectiveness of this new method,the traditional and the proposed new device are used to test the PDC of cable samples in the laboratory as well as in an industrial environment.It is worth noting that there is almost no interference on the Earth wire in the laboratory environment but massive interference in the industrial environment using a traditional method of PDC measurement from ground or Earth wire.The new method of high-voltage testing can efficiently eliminate the interference and accurately measure PDC in a strong industrial interference environment.Furthermore,the wiring of this new method and device is relatively simple,which is convenient for industrial applications.
文摘Silicone rubber(SiR)composite material is a modern-day insulator for high voltage outdoor applications.The imperfection attributed to SiR is its weak resistance to tracking and erosion when exposed to an outdoor polluted environment which reduces its operational lifetime.This paper investigates the performance of SiR with the addition of 0,1,2.5,5,10 and 20%by weight contents of nano alumina(Al_(2)O_(3)).Inclined plane tests are performed according to IEC 60587 using the step up tracking voltage method with an initial voltage of 3.0 kV and the contaminant solution flow rate is maintained at 0.3 ml/min using a peristaltic pump.The applied voltage level is increased at a rate of 0.25 kV/h.Results suggest that physical tracking,erosion,RMS leakage current and surface partial discharge(PD)performance of samples is improved with the addition of nano alumina.The tracking length,eroded mass,RMS leakage current and average PD magnitude are measured 22%,79%,30%and 52%lesser in 20 wt%relative to 0 wt%,respectively.A thermal distribution analysis is undertaken with infrared camera and it is discovered that heat is accumulated in the discharge area of the liquid flow.The maximum temperature on the insulating specimen is decreased with increasing nanofiller contents.The above promising findings can be due to better thermal stability with low chain mobility at the interaction zone of SiR and alumina.Moreover,less liquid evaporation due to better thermal conduction and improved physical bonding between SiR and nano alumina are possible reasons behind the excellent performance of nanocomposites.
基金financially through the Fulbright Postdoctoral-Vice Chancellor’s Postdoctoral Research Fellowship.
文摘Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once ignited,substantially reduce its working life.This paper attempts to investigate tracking/erosion performance of room temperature vulcanized(RTV)silicone rubber along with flame retardant parameters using aluminum trihydrate(ATH),graphene nanosheets(GN)and milled glass fiber(GF)additives.The inclined plane test(IPT)was performed in line with criteria defined in IEC 60587 using step-up tracking voltage method while flame retardancy is evaluated according to ASTM E 1354.0 using a cone calorimeter.Results suggest 30% of ATH assists in improving physical tracking/erosion resistance of pristine silicone elastomer rubber by impeding development of leakage current and a great reduction in maximum average temperatures on the surface of RTV2.Further improvement in performance of RTV2 is achieved through introduction of 1%of GN and 5% of GF as seen in RTV4.Moreover,30% of ATH reduces heat release rate and smoke production rate,and this trend is improved with the introduction of GN/GF.RTV4 has pop up as the most promising silicone rubber composite with excellent electrical tracking,erosion,and flame resistance performance relative to its counterparts in this study.
