When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this...When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this study,the COMSOL software is used to simulate such a process for the FXBW4-10/100 composite insulator with or without water droplets condensation under a 10 kV DC voltage.The influence of the wind speed and particles concentration on the contamination characteristics of the considered 110 kV insulator is analyzed.The results show that:1)in the presence of water droplets on the insulator surface,the ratio of electrical field force and gravity acting on the particles is large;2)the contamination on the insulator surface increases with the wind speed;3)when the wind speed is small,the relationship between the contamination amount and the pollution concentration is essentially linear.展开更多
As an important component of oil-immersed transformers,the bushing's internal insu-lation ageing and dampness after the long-term operation can cause changes in the in-ternal electric and temperature fields,seriou...As an important component of oil-immersed transformers,the bushing's internal insu-lation ageing and dampness after the long-term operation can cause changes in the in-ternal electric and temperature fields,seriously threatening its safe operation.This paper tested the power frequency permittivity and direct current conductivity of aged and damp oil-paper insulation samples at different testing temperatures,and constructed a dynamic dielectric parameter calculation model.Meanwhile,a simulation model was established based on the actual structure of the 252 kV/1250 A bushing which is mainly used for the oil-immersed high-voltage bushings of 110 kV and above.The electric-magnetic-thermal multi-physical fields were used for simulation analysis.The influence of ageing/moisture(different degrees of dampness in the upper and lower regions)on the electric field distribution in the bushing was obtained.During the initial to steady-state process,the electric field distribution at the zero and end shield shows a reversal phenomenon.When the capacitor core has different degrees of dampness in the upper and lower regions,the impedance distribution of the capacitor core is non-uniform.This phenomenon will lead to an increase in the radial electric field gradient at the end shield of the capacitor core,which is prone to the risk of slip-flashing discharge.In summary,this paper adopts the field-induced dynamic parameters method to analyse the changes of multi-physical fields in the bushing.This can provide theoretical guidance for optimising the bushing structure and on-site maintenance.展开更多
Insulation failures of epoxy spacers applied in gas insulated transmission line/switchgear(GIL/GIS)often occur,primarily due to electric field distortion.In this paper,a field graded coating CaCu_(3)Ti_(4)O_(12)(CCTO)...Insulation failures of epoxy spacers applied in gas insulated transmission line/switchgear(GIL/GIS)often occur,primarily due to electric field distortion.In this paper,a field graded coating CaCu_(3)Ti_(4)O_(12)(CCTO)is presented to enhance the flashover performance of a GIL/GIS spacer.First,CCTO layers of different thicknesses are deposited on the spacer surface using magnetron sputtering technology.Then,insulating properties of these sputtered spacers under alternating current,direct current,and polarity reversal(PR)voltages and with the existence of metal particles are researched by experimental and simulation methods.Results show the short-term(30 and 60 min)sputtering treatments have no obvious effect on improving insulating properties.展开更多
Layered epoxy/paper composites that exhibit excellent insulating characteristics under elevated electrification and temperature conditions are essential components for power system insulation.Yet,inevitable charge acc...Layered epoxy/paper composites that exhibit excellent insulating characteristics under elevated electrification and temperature conditions are essential components for power system insulation.Yet,inevitable charge accumulation occurs at hetero interfaces between layers due to interfacial polarisation and interface barrier effect,bringing about local electric field distortion and potential risk of partial discharge.A fundamental challenge is either to obtain accurate interface charge behaviours of in-service multi-layer insulating composites,or to construct verified simulating models for replacing experiments.Herein,a modified bipolar charge transport model to simulate interface charge behaviours in layered composites is proposed.With model parameters directly originated from equivalent experiments(e.g.conduction current measurement,thermally stimulated depolarisation current testing,and ultraviolet-visible spectroscopy)of epoxy/paper composites,the simulated temperature-dependent interface charge characteristics match well with pulsed electro-acoustic results.Furthermore,electrical thresholds can also be accurately calculated using such models(maximum deviation of 8.44%from experimental results),providing references for optimised insulation structural design.展开更多
The electrically charged wear debris generated inside the conductive slip ring of spacecraft not only exacerbates the wear of the ring channel but also causes distortion of the electric field,which can induce surface ...The electrically charged wear debris generated inside the conductive slip ring of spacecraft not only exacerbates the wear of the ring channel but also causes distortion of the electric field,which can induce surface flashover in vacuum,seriously affecting the operational reliability of solar array panels.This study is based on the space station experimental cabin’s on-orbit technology testing platform,and it systematically investigates the wear debris migration behavior of the brush-slip ring mechanism.Through long-term on-orbit testing observations,a three-dimensional multiphysics coupling model was developed using a Monte Carlo-Finite Element joint algorithm.This model reveals the migration mechanism of wear debris under the combined effect of the electrostatic field and electron radiation field:debris without initial velocity primarily adheres to the metal ring surface;debris with initial velocity migrates towards the shield with a speed of up to 0.0136 m/s in the electrostatic field,while a small amount adheres to the side of the insulating baffle due to electric field distortion near the brush;under the electron radiation combined field,the surface potential reconstruction of the dielectric increases the local field strength to 2.2×10^(8)V/m,significantly enhancing the migration trend of the debris towards the insulating baffle and causing the debris on the inner side of the shield to detach and impact the baffle.The study accurately reproduced the spatial distribution characteristics of the wear debris and revealed the discharge behavior induced by the debris through trajectory prediction models and comparison with on-orbit experimental data.This provides theoretical support for the insulation reliability design of space electromechanical products.展开更多
High electric field and temperatures can result in electrical property degradation of oil-paper insulation and accelerate its aging process.This paper describes the regulation of space charge in the process of electro...High electric field and temperatures can result in electrical property degradation of oil-paper insulation and accelerate its aging process.This paper describes the regulation of space charge in the process of electro-thermal aging.Electric field distortion and differences in characteristic parameters during electro-thermal aging are analyzed,along with the effects of electro-thermal aging on space charge from the perspective of trap energy.High temperature and an electric field are used to accelerate the aging of oil-paper,and space charge characteristics are measured using the pulsed electro-acoustic(PEA)method throughout the electro-thermal aging.Based on results obtained,it can be concluded that homo-charge injection occurs at the anode and the type of the charge injection at the cathode varies throughout the electro-thermal aging;the decrease of permittivity during aging allows for space charge injection to take place;growth of trap depth makes the space charge accumulate in the middle of the sample;and space charge accumulation after electro-thermal aging results in inner electric field distortion,which leads to large current and decreased breakdown in voltages.展开更多
基金Science and Technology Project of State Grid Corporation(GY7111053)[www.sgcc.com.cn]。
文摘When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this study,the COMSOL software is used to simulate such a process for the FXBW4-10/100 composite insulator with or without water droplets condensation under a 10 kV DC voltage.The influence of the wind speed and particles concentration on the contamination characteristics of the considered 110 kV insulator is analyzed.The results show that:1)in the presence of water droplets on the insulator surface,the ratio of electrical field force and gravity acting on the particles is large;2)the contamination on the insulator surface increases with the wind speed;3)when the wind speed is small,the relationship between the contamination amount and the pollution concentration is essentially linear.
基金National Natural Science Foundation of China,Grant/Award Number:52307164Heilongjiang Provincial Natural Science Foundation of China,Grant/Award Number:YQ2024E044。
文摘As an important component of oil-immersed transformers,the bushing's internal insu-lation ageing and dampness after the long-term operation can cause changes in the in-ternal electric and temperature fields,seriously threatening its safe operation.This paper tested the power frequency permittivity and direct current conductivity of aged and damp oil-paper insulation samples at different testing temperatures,and constructed a dynamic dielectric parameter calculation model.Meanwhile,a simulation model was established based on the actual structure of the 252 kV/1250 A bushing which is mainly used for the oil-immersed high-voltage bushings of 110 kV and above.The electric-magnetic-thermal multi-physical fields were used for simulation analysis.The influence of ageing/moisture(different degrees of dampness in the upper and lower regions)on the electric field distribution in the bushing was obtained.During the initial to steady-state process,the electric field distribution at the zero and end shield shows a reversal phenomenon.When the capacitor core has different degrees of dampness in the upper and lower regions,the impedance distribution of the capacitor core is non-uniform.This phenomenon will lead to an increase in the radial electric field gradient at the end shield of the capacitor core,which is prone to the risk of slip-flashing discharge.In summary,this paper adopts the field-induced dynamic parameters method to analyse the changes of multi-physical fields in the bushing.This can provide theoretical guidance for optimising the bushing structure and on-site maintenance.
基金supported in part by the National Natural Science Foundation of China(51807136 and 52377153).
文摘Insulation failures of epoxy spacers applied in gas insulated transmission line/switchgear(GIL/GIS)often occur,primarily due to electric field distortion.In this paper,a field graded coating CaCu_(3)Ti_(4)O_(12)(CCTO)is presented to enhance the flashover performance of a GIL/GIS spacer.First,CCTO layers of different thicknesses are deposited on the spacer surface using magnetron sputtering technology.Then,insulating properties of these sputtered spacers under alternating current,direct current,and polarity reversal(PR)voltages and with the existence of metal particles are researched by experimental and simulation methods.Results show the short-term(30 and 60 min)sputtering treatments have no obvious effect on improving insulating properties.
基金Science and Technology Project of State Grid Corporation of China,Grant/Award Number:SGLNDK00KJJS1900250。
文摘Layered epoxy/paper composites that exhibit excellent insulating characteristics under elevated electrification and temperature conditions are essential components for power system insulation.Yet,inevitable charge accumulation occurs at hetero interfaces between layers due to interfacial polarisation and interface barrier effect,bringing about local electric field distortion and potential risk of partial discharge.A fundamental challenge is either to obtain accurate interface charge behaviours of in-service multi-layer insulating composites,or to construct verified simulating models for replacing experiments.Herein,a modified bipolar charge transport model to simulate interface charge behaviours in layered composites is proposed.With model parameters directly originated from equivalent experiments(e.g.conduction current measurement,thermally stimulated depolarisation current testing,and ultraviolet-visible spectroscopy)of epoxy/paper composites,the simulated temperature-dependent interface charge characteristics match well with pulsed electro-acoustic results.Furthermore,electrical thresholds can also be accurately calculated using such models(maximum deviation of 8.44%from experimental results),providing references for optimised insulation structural design.
文摘The electrically charged wear debris generated inside the conductive slip ring of spacecraft not only exacerbates the wear of the ring channel but also causes distortion of the electric field,which can induce surface flashover in vacuum,seriously affecting the operational reliability of solar array panels.This study is based on the space station experimental cabin’s on-orbit technology testing platform,and it systematically investigates the wear debris migration behavior of the brush-slip ring mechanism.Through long-term on-orbit testing observations,a three-dimensional multiphysics coupling model was developed using a Monte Carlo-Finite Element joint algorithm.This model reveals the migration mechanism of wear debris under the combined effect of the electrostatic field and electron radiation field:debris without initial velocity primarily adheres to the metal ring surface;debris with initial velocity migrates towards the shield with a speed of up to 0.0136 m/s in the electrostatic field,while a small amount adheres to the side of the insulating baffle due to electric field distortion near the brush;under the electron radiation combined field,the surface potential reconstruction of the dielectric increases the local field strength to 2.2×10^(8)V/m,significantly enhancing the migration trend of the debris towards the insulating baffle and causing the debris on the inner side of the shield to detach and impact the baffle.The study accurately reproduced the spatial distribution characteristics of the wear debris and revealed the discharge behavior induced by the debris through trajectory prediction models and comparison with on-orbit experimental data.This provides theoretical support for the insulation reliability design of space electromechanical products.
基金supported by National Basic Research Program of China(973 Program)under Grant 2011CB209400。
文摘High electric field and temperatures can result in electrical property degradation of oil-paper insulation and accelerate its aging process.This paper describes the regulation of space charge in the process of electro-thermal aging.Electric field distortion and differences in characteristic parameters during electro-thermal aging are analyzed,along with the effects of electro-thermal aging on space charge from the perspective of trap energy.High temperature and an electric field are used to accelerate the aging of oil-paper,and space charge characteristics are measured using the pulsed electro-acoustic(PEA)method throughout the electro-thermal aging.Based on results obtained,it can be concluded that homo-charge injection occurs at the anode and the type of the charge injection at the cathode varies throughout the electro-thermal aging;the decrease of permittivity during aging allows for space charge injection to take place;growth of trap depth makes the space charge accumulate in the middle of the sample;and space charge accumulation after electro-thermal aging results in inner electric field distortion,which leads to large current and decreased breakdown in voltages.
