It is necessary to find an efficient selection method to pre-analyze the gas electric strength from the perspective of molecule structure and the properties for finding the alternative gases to sulphur hexafluoride （...It is necessary to find an efficient selection method to pre-analyze the gas electric strength from the perspective of molecule structure and the properties for finding the alternative gases to sulphur hexafluoride （SF6）. As the properties of gas are determined by the gas molecule structure, the research on the relationship between the gas molecule structure and the electric strength can contribute to the gas pre-screening and new gas development. In this paper, we calculated the vertical electron affinity, molecule orbits distribution and orbits energy of gas molecules by the means of density functional theory （DFT） for the typical structures of organic gases and compared their electric strengths. By this method, we find part of the key properties of the molecule which are related to the electric strength, including the vertical electron affinity, the lowest unoccupied molecule orbit （LUMO） energy, molecule orbits distribution and negativeion system energy. We also listed some molecule groups such as unsaturated carbons double bonds （C=C） and carbonitrile bonds （C=N） which have high electric strength theoretically by this method.展开更多
In order to guarantee safe operations, low energy discharge within gas insulated switchgear （GIS） should be detected as soon as possible before they develop severely and cause final breakdown failures. This paper ai...In order to guarantee safe operations, low energy discharge within gas insulated switchgear （GIS） should be detected as soon as possible before they develop severely and cause final breakdown failures. This paper aims to present a GIS discharge diagnosis technique adopting gaseous decompositions. To reach this aim, needle-plate electrode and the sphere-plate electrode with metallic particles on the plate are designed to simulate two kinds of low energy discharge, namely, corona discharge and spark discharge, respectively. After sampling and analyzing the gases, different yields of gaseous by-products under different types of low energy discharge are obtained. Based on the decomposition mechanisms reported by previous researches and the experiment results, it can be concluded that S2OF10, SO2F2 , and SO2 can be used as the characteristic gas to identify low energy discharge; the increment of S2OF10 can indicate the occurrence of low energy discharges while the volume ratio between SO2F2 and SO2 can define the type of low energy discharge.展开更多
Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this ...Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.展开更多
Gas-insulated equipment(GIE)that utilizes the most potent greenhouse gas sulfur hexafluoride(SF_(6))as insulation and arc-quenching medium has been widely used in the power industry.Seeking eco-friendly insulating gas...Gas-insulated equipment(GIE)that utilizes the most potent greenhouse gas sulfur hexafluoride(SF_(6))as insulation and arc-quenching medium has been widely used in the power industry.Seeking eco-friendly insulating gas with advanced performance for next-generation SF_(6)-free GIE is significant for the“net-zero”goal and sustainable development.In this paper,the utilization,emission,and reduction policies of SF_(6)around the world were summarized first.Then,we systematically reviewed the latest progress in comprehensive performance evaluation of eco-friendly insulating gas in terms of molecular design,dielectric insulation,arc-quenching,stability and decomposition,materials compatibility,biosafety,etc.Further,the representative applications of eco-friendly insulating gas in medium-voltage,high-voltage GIE as well as relevant maintenance-related technologies were highlighted.Accordingly,the existing challenges and future perspectives were proposed,presenting a roadmap to hopefully steer the development of eco-friendly insulating gas and GIE.展开更多
In the electric power equipment industry,various insulating materials and accessories are manufactured using petroleum-based epoxy resins.However,petrochemical resources are gradually becoming limited.In addition,the ...In the electric power equipment industry,various insulating materials and accessories are manufactured using petroleum-based epoxy resins.However,petrochemical resources are gradually becoming limited.In addition,the global surge in plastic usage has consistently raised concerns regarding greenhouse gas emissions,leading to worsening global warming.Therefore,to facilitate eco-friendly policies,industrialising epoxy systems applicable to high-pressure components using bio-based epoxy composites is essential.The results of the characterisation conducted in this research regarding bio-content were confirmed through thermogravimetric analysis and differential scanning calorimetry,which showed that as the bio-content increased,the thermal stability improved.Considering the operating temperature of 105℃ for the insulation spacer,structurally,no issues would be encountered if the spacer was manufactured with a bio-content of 20%(bio 20%).Subsequent tensile and flexural strength measurements revealed mechanical properties equivalent to or better than those of their petroleum-based counterparts.The impact strength tended to decrease with increasing bio-content.Analysing the dielectric properties confirmed that the epoxy composite containing 20%biomaterial is suitable for manufacturing insulation spacers.Subsequently,a series of tests conducted after spacer fabrication confirmed the absence of internal metals and bubbles with no external discolouration or cracks observed.展开更多
In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The...In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The general arcing model is not able to give a good description of the arc development process. In this paper, based on the physical process of arcing and existing arc models （the exponential time-varying resistance model and the segmental arcing models）, a dy- namic arcing model is proposed, which is divided into two stages before and after the zero crossing. The dynamic arcing model combines hyperbola time-varying resistance and the Mayr model to describe the dynamic process of arcing. The present paper creates an arc model blockset upon the Matlab/Simulink software platform. Moreover for a specific 1100 kV station, VFTO is simulated in detail based on different arcing models. It is demonstrated that the dynamic arcing model can describe the physical arc process precisely and is useful for improving the accuracy of VFTO simulations.展开更多
Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These c...Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices.The smaller the size of the cell,the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test.To overcome this problem,a calibration procedure using a gigahertz transverse electromagnetic (GTEM) test cell and a pulsed signal source were introduced in 1997.Although this procedure has many advantages and is easy to understand,measurements show several shortcomings of this calibration method.To overcome the disadvantages of the known systems,a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested.The UHF sensor was placed in a region with minimum distortion of the electric field due to its installation.Experience shows that the new method for calibrating UHF sensors is necessary in order to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections.Due to its surprisingly simple structure,its low price and low overall measurement uncertainty,it is the preferred method for calibrating UHF sensors for GIS applications.展开更多
This paper describes a realizable fabrication method to manufacture chemical gas sensors by using singlewalled carbon nanotubes(SWCNTs).The sensors were tested for the monitoring of SF_6 decomposition gas produced by ...This paper describes a realizable fabrication method to manufacture chemical gas sensors by using singlewalled carbon nanotubes(SWCNTs).The sensors were tested for the monitoring of SF_6 decomposition gas produced by partial discharge(PD) in GIS tank.The results showed a superior sensitivity,favorable reliability and good reproducibility. For further clarifying the relativity between sensor response and partial discharge activity,the discharge in GIS tank was monitored simultaneously through conventional pulse current method and a SWCNTs gas sensor,and the measurement results were put together for comparative analysis in this paper.The sensor response showed a great dependence on partial discharge characteristics.The sensor response increased nearly linearly with limits when the energy of discharge was persistently accumulated.Partial discharge power had a great influence on the response rate and the time delay.With the increase of partial discharge power,the response rate augmented almost in proportion while the time delay gradually becomes shorter with limits.The results were quite favorable to assess the partial discharge intensity and duration to some extent.Compared with pulse current method,the sensor was predominant to detect partial discharge exposed to constantly high levels of noise.It was capable of detecting partial discharge which was too weak to be detected with pulse current method.However,the sensor response didn't show much dependency on the apparent discharge of partial discharge.展开更多
An increasing number of large-scale renewable plants are generating abundant electricity. As power-to-gas and power-to-x technologies become promising ways to utilize surplus electricity to enhance the flexibility of ...An increasing number of large-scale renewable plants are generating abundant electricity. As power-to-gas and power-to-x technologies become promising ways to utilize surplus electricity to enhance the flexibility of energy systems, an innovative gas-electricity integrated transmission system (GEITS) to co-transmit electricity and hydrogen or other gas products is proposed, with the foreseeable advantages of compact structure, lower installation cost, and larger energy capacity. This paper investigates the feasibility of GEITS, suggests a design guideline, and gives the operation technical parameters of GEITS in different application scenarios. The dimensions and operating pressures of GEITS benchmark natural gas pipelines and then the nominal voltages of GEITS are calculated based on the electrical strength of high-pressure hydrogen. The nominal ampacities of GEITS are evaluated by temperature-rising simulations, which are larger than those of other transmission lines. Furthermore, high-pressure flowing hydrogen acting as an electrical insulator is a novel topic, and it is investigated via experimental validation on a scale model. Although the effect of 0.4 m/s flowing hydrogen on discharge characteristics has not been observed compared to static hydrogen, the discharge is impaired in 2.4 m/s flowing nitrogen. Future works will investigate the electrical strength of high-pressure long-distance hydrogen gaps under lightning impulse tests and the discharge phenomenon in higher flowing-velocity hydrogen. Methane and methane blended with hydrogen with higher insulation performance can increase the nominal voltages.展开更多
CF_(4)is a major decomposition product of the insulating gas in C_(4)F_(7)N-insulated gasinsulated metal-enclosed switchgear(GIS)during partial discharge or overheating faults.Its detection is essential for effective ...CF_(4)is a major decomposition product of the insulating gas in C_(4)F_(7)N-insulated gasinsulated metal-enclosed switchgear(GIS)during partial discharge or overheating faults.Its detection is essential for effective online monitoring and fault diagnosis of GIS.However,the application of photoacoustic spectroscopy for CF_(4)detection is hampered by significant cross-interference from the background C_(4)F_(7)N gas.In this paper,quantum chemical calculations revealed that C_(4)F_(7)N hydrolyses to form perfluoroisobutyrate and ammonia under base catalysis,exhibiting a low reaction energy barrier and high Gibbs free energy change,indicating ease of initiation and substantial reaction extent.This chemical specificity,unlike the stable CF_(4)which does not undergo such a reaction,enables selective purification of the gas to be detected through this hydrolysis reaction.Leveraging this insight,an experimental system was constructed that cascades chemical absorption purification with photoacoustic spectroscopy detection.This system effectively mitigates the cross-interference of C_(4)F_(7)N in CF_(4)detection by selectively absorbing C_(4)F_(7)N with over 95%efficiency through a base-catalysed nucleophilic hydrolysis reaction.This enabled the precise detection of trace amounts of CF_(4)against a substantial background of C_(4)F_(7)N with a detection limit reaching 14.79μL/L.This advancement offers support for the online monitoring and fault diagnosis of eco-friendly GIS.展开更多
C_(5)F_(10)O/CO_(2)gas mixture is one of the most promising alternatives to SF_(6)as an insulating gas in high-voltage switchgear.As a key performance index in product design,the temperature rise characteristics are r...C_(5)F_(10)O/CO_(2)gas mixture is one of the most promising alternatives to SF_(6)as an insulating gas in high-voltage switchgear.As a key performance index in product design,the temperature rise characteristics are rarely reported.In this paper,the thermodynamic parameters of C_(5)F_(10)O/CO_(2)gas mixture were calculated first.Then,the calculation model of transient temperature rise was constructed for a 252 kV/3150 A bus,and a temperature rise experimental platform was built to verify the reliability of the proposed calculation model.On this basis,the influence of different factors such as load current,charging pressure,mixing ratio,and structure size on the temperature rise of the bus was further analysed,and it is found that increasing the charging pressure and the mixing ratio of C5F10O could effectively reduce the bus temperature rise but it still could not reach the level of SF_(6).The main structure size that affects the temperature rise of the bus is the outer diameter of the conductor,which increases by 10.2%,and the temperature rise is the same as that of the original SF_(6)bus.Finally,a high-precision bus temperature rise surrogate model,which combined with the Latin hypercube model,the coefficient of prognosis,and the Kriging fitting method was established to facilitate the structural design.展开更多
In this paper,we compare the differences in the charge accumulation for two different models about conductivity:one in which the conductivity value of the spacer is invariant with time(steady-state conductivity,Model...In this paper,we compare the differences in the charge accumulation for two different models about conductivity:one in which the conductivity value of the spacer is invariant with time(steady-state conductivity,ModelⅠ)and one in which the conductivity value can vary dynamically with time(dynamic conductivity,ModelⅡ).The time for the potential distribution to reach a stable state is 8078 s in ModelⅠand 7932 s in ModelⅡ.After the charge accumulation reaches saturation,the charges migrate to the middle of the spacer under the applied electric field.Maximum tangential field strength is 2.56×10^(6)V/m in ModelⅠand 2.84×5 C/m^(3),which is much smaller than the charge density in the spacer.The mechanism underlying the charge accumulation phenomenon is the differences in the conductivity value distribution caused by a time-varying temperature gradient field.This paper can provide a more precise theoretical basis for the selection and modification of HVDC-GIL spacer.展开更多
Perfluoroisobutyronitrile(C_(4)F_(7)N)is recognised as the next-generation dielectric medium for eco-friendly gas-insulated equipment(GIE).However,there is gas metal incompatibility in strong electromagnetic environme...Perfluoroisobutyronitrile(C_(4)F_(7)N)is recognised as the next-generation dielectric medium for eco-friendly gas-insulated equipment(GIE).However,there is gas metal incompatibility in strong electromagnetic environments and environmentally friendly insulating gas atmospheres that endangers the operational safety and service life of GIE.Here,a solvent-induced grain boundary reconstruction method was proposed to prepare corrosion-resistant copper rapidly.Accordingly,the partial dischargeinduced gas-metal interaction was simulated and the corrosion resistance properties of copper were evaluated.Additionally,the gas-solid interaction mechanism was investigated and the improvement mechanism of the proposed method on the stability of the gas-solid interface was discussed.Related results provide a reference for the development and application reliability of C_(4)F_(7)N-based eco-friendly GIE.展开更多
Partial discharge(PD)detection is considered one of the most crucial and effective methods for identifying defects in electrical equipment.Consequently,investigating advanced and efficient PD monitoring techniques is ...Partial discharge(PD)detection is considered one of the most crucial and effective methods for identifying defects in electrical equipment.Consequently,investigating advanced and efficient PD monitoring techniques is essential for the development of gas-insulated equipment(GIE)and the construction of ultra-high-voltage(UHV)networks.This paper first explores the causes and impact characteristics of various defects in GIE based on experimental results and simulation analysis.It then reviews current research on advanced PD measurement techniques,integrating acoustic,chemical and optical methods.The findings preliminarily demonstrate the unique advantages and applicability of the advanced methods for complex detection environments.Finally,this paper ad-dresses the technical challenges and potential breakthroughs associated with these detection techniques.In this regard,this study aims to provide technical insights and research directions for defect detection techniques in UHV GIE.展开更多
Within 30 min after live operation of gas-insulated switchgear(GIS),more than 60%of discharge failures are caused by metallic particles.To address this issue,this study explored the vibration propagation mechanisms in...Within 30 min after live operation of gas-insulated switchgear(GIS),more than 60%of discharge failures are caused by metallic particles.To address this issue,this study explored the vibration propagation mechanisms in GIS cavities and established an equivalent vibration transmission model.A kinetic energy transfer conservation model between the cavity and particles was constructed,systematically analyzing the critical factors affecting the particle starting field strength and explicitly formulating the criterion for vibration-induced particle activation.The electric field distortion caused by particle rotation was investigated,and a collision dynamics model characterizing rotational mo-tion was developed.By analyzing the critical conditions for stable and rotational motion,the corresponding criterion was derived.The results showed that the electric field distortion caused by flaky particles increases with the rotation angle.Vibration effectively activates particles and enhances their mobility.The discharge risk is positively correlated with vibration intensity and particle thickness,but negatively correlated with particle size.This paper clarifies the motion mechanism of flaky metal particles in GIS under shock vibration,providing support for solving the problem of frequent faults after GIS live operation.展开更多
Gas-insulated switchgear(GIS)plays a critical role in ensuring the reliability of power systems,but partial discharge(PD)is a primary cause of failures within GIS equipment.Traditional PD diagnostic methods rely heavi...Gas-insulated switchgear(GIS)plays a critical role in ensuring the reliability of power systems,but partial discharge(PD)is a primary cause of failures within GIS equipment.Traditional PD diagnostic methods rely heavily on laboratory data,which differ signifi-cantly from that under the complex conditions of field data,leading to a marked drop in recognition accuracy when they are applied to field PD diagnosis.This study addresses the challenge by integrating field data into the training process,utilising a deep transfer learning approach that combines laboratory and field data to improve diagnostic accuracy for GIS PD.The research collected PD data from laboratory models representing five defect types and field data gathered from operational GIS equipment.A deep residual network(ResNet50)was pretrained using laboratory data and fine-tuned with field data through deep transfer learning to optimise the recognition of PD in field conditions.The results show that the proposed model achieves a significantly higher recognition accuracy(93.7%)for field data compared to traditional methods(60%-70%).The integration of deep transfer learning ensures that both low-dimensional general features from labora-tory data and high-dimensional specific features from field data are effectively utilised.This research significantly contributes to improving the diagnostic accuracy of PD in GIS under field conditions,providing a robust method for defect detection in operational equipment.展开更多
Accurately identifying the location and type of internal defects in gas-insulated switchgear(GIS)is a challenge.To address this challenge,this study proposes a novel method for the nondestructive detection of GIS inte...Accurately identifying the location and type of internal defects in gas-insulated switchgear(GIS)is a challenge.To address this challenge,this study proposes a novel method for the nondestructive detection of GIS internal defects.This method is based on x-ray digital radiography(X-DR)technology and an improved real-time models for object detection(RTMdet)algorithm,namely GIS-specific localised internal defect-RTMdet.Firstly,the X-DR images of GIS are preprocessed by dynamic limit adaptive histogram equalisation algorithm to improve the images contrast.Then,a convolution shuffle upsample module for upsampling is proposed,which enlarges the defect feature map by multi-convolution and pixel shuffling,reduces the information loss,and enhances the interaction between the feature information.Finally,both the multi-channel attention net and the global attention mechanism are integrated into the neck network for enhancing local feature extraction and global information association.Experiments demonstrate that the pro-posed method achieves a mean average precision@0.5:0.95 of 94.9%,showcasing excellent overall performance and generalisation ability,and is more suitable for accurate nondestructive detection of internal defects of GIS in complex scenarios.展开更多
Mechanical vibration defect is the key factor leading to sudden failure of gas-insulated switchgear(GIS)equipment.It is important to realise effective prediction of the me-chanical vibration state development trend of...Mechanical vibration defect is the key factor leading to sudden failure of gas-insulated switchgear(GIS)equipment.It is important to realise effective prediction of the me-chanical vibration state development trend of GIS equipment in order to improve its active safety protection level.This paper carried out research on the accurate prediction method and experimental validation of the mechanical vibration state and its defect severity development trend for the GIS equipment.Firstly,the deep and shallow vibration feature parameters for different mechanical defect signals were jointly extracted by time-domain features and deep belief network methods.Secondly,a new prediction model,incorporating the attention mechanism and the bidirectional gated recurrent unit(BiGRU),was constructed with the deep and shallow vibration feature parameters as inputs.Finally,the prediction trend effectiveness was verified based on the real-type GIS mechanical simulation platform and the field operation GIS equipment.Results show that the deep and shallow vibration feature extraction method proposed in this paper can characterise the mechanical defect information more comprehensively.The new prediction method of the vibration state trend based on the attention-BiGRU model shows ideal accuracy,and the predicted vibration state development trend is highly consistent with the actual,with an average absolute error of 0.063.The root mean square error(ERMSE)value of the prediction method is<5%,which reduces the relative error value at least 37% compared with the traditional prediction models.This paper provides a valuable reference for the proactive defence of GIS mechanical failure.展开更多
基金supported by National Natural Science Foundation of China(Nos.51177101 and 51337006)
文摘It is necessary to find an efficient selection method to pre-analyze the gas electric strength from the perspective of molecule structure and the properties for finding the alternative gases to sulphur hexafluoride （SF6）. As the properties of gas are determined by the gas molecule structure, the research on the relationship between the gas molecule structure and the electric strength can contribute to the gas pre-screening and new gas development. In this paper, we calculated the vertical electron affinity, molecule orbits distribution and orbits energy of gas molecules by the means of density functional theory （DFT） for the typical structures of organic gases and compared their electric strengths. By this method, we find part of the key properties of the molecule which are related to the electric strength, including the vertical electron affinity, the lowest unoccupied molecule orbit （LUMO） energy, molecule orbits distribution and negativeion system energy. We also listed some molecule groups such as unsaturated carbons double bonds （C=C） and carbonitrile bonds （C=N） which have high electric strength theoretically by this method.
基金Supported by the Scotland-China Higher Education Research Partnership for Ph. D. Studies ([2010]6044)
文摘In order to guarantee safe operations, low energy discharge within gas insulated switchgear （GIS） should be detected as soon as possible before they develop severely and cause final breakdown failures. This paper aims to present a GIS discharge diagnosis technique adopting gaseous decompositions. To reach this aim, needle-plate electrode and the sphere-plate electrode with metallic particles on the plate are designed to simulate two kinds of low energy discharge, namely, corona discharge and spark discharge, respectively. After sampling and analyzing the gases, different yields of gaseous by-products under different types of low energy discharge are obtained. Based on the decomposition mechanisms reported by previous researches and the experiment results, it can be concluded that S2OF10, SO2F2 , and SO2 can be used as the characteristic gas to identify low energy discharge; the increment of S2OF10 can indicate the occurrence of low energy discharges while the volume ratio between SO2F2 and SO2 can define the type of low energy discharge.
文摘Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.
基金supported in part by the National Natural Science Foundation of China(Nos.52277144,52107145,and 51907023)the fellowship of China Postdoctoral Science Foundation(No.2022M712446).
文摘Gas-insulated equipment(GIE)that utilizes the most potent greenhouse gas sulfur hexafluoride(SF_(6))as insulation and arc-quenching medium has been widely used in the power industry.Seeking eco-friendly insulating gas with advanced performance for next-generation SF_(6)-free GIE is significant for the“net-zero”goal and sustainable development.In this paper,the utilization,emission,and reduction policies of SF_(6)around the world were summarized first.Then,we systematically reviewed the latest progress in comprehensive performance evaluation of eco-friendly insulating gas in terms of molecular design,dielectric insulation,arc-quenching,stability and decomposition,materials compatibility,biosafety,etc.Further,the representative applications of eco-friendly insulating gas in medium-voltage,high-voltage GIE as well as relevant maintenance-related technologies were highlighted.Accordingly,the existing challenges and future perspectives were proposed,presenting a roadmap to hopefully steer the development of eco-friendly insulating gas and GIE.
基金Technology Innovation Program,Grant/Award Number:20010965Human Resources Development of the Korea Institute of Energy Technology Evaluation and Planning,Grant/Award Number:RS-2023-00266248。
文摘In the electric power equipment industry,various insulating materials and accessories are manufactured using petroleum-based epoxy resins.However,petrochemical resources are gradually becoming limited.In addition,the global surge in plastic usage has consistently raised concerns regarding greenhouse gas emissions,leading to worsening global warming.Therefore,to facilitate eco-friendly policies,industrialising epoxy systems applicable to high-pressure components using bio-based epoxy composites is essential.The results of the characterisation conducted in this research regarding bio-content were confirmed through thermogravimetric analysis and differential scanning calorimetry,which showed that as the bio-content increased,the thermal stability improved.Considering the operating temperature of 105℃ for the insulation spacer,structurally,no issues would be encountered if the spacer was manufactured with a bio-content of 20%(bio 20%).Subsequent tensile and flexural strength measurements revealed mechanical properties equivalent to or better than those of their petroleum-based counterparts.The impact strength tended to decrease with increasing bio-content.Analysing the dielectric properties confirmed that the epoxy composite containing 20%biomaterial is suitable for manufacturing insulation spacers.Subsequently,a series of tests conducted after spacer fabrication confirmed the absence of internal metals and bubbles with no external discolouration or cracks observed.
基金supported by Special Research Fund for Doctoral Program of Education Ministry of China (No. 20092102110001)Natural Science Foundation of Liaoning Province of China (No. 201102169)National Natural Science Foundation of China (No. 51277123)
文摘In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The general arcing model is not able to give a good description of the arc development process. In this paper, based on the physical process of arcing and existing arc models （the exponential time-varying resistance model and the segmental arcing models）, a dy- namic arcing model is proposed, which is divided into two stages before and after the zero crossing. The dynamic arcing model combines hyperbola time-varying resistance and the Mayr model to describe the dynamic process of arcing. The present paper creates an arc model blockset upon the Matlab/Simulink software platform. Moreover for a specific 1100 kV station, VFTO is simulated in detail based on different arcing models. It is demonstrated that the dynamic arcing model can describe the physical arc process precisely and is useful for improving the accuracy of VFTO simulations.
文摘Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices.The smaller the size of the cell,the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test.To overcome this problem,a calibration procedure using a gigahertz transverse electromagnetic (GTEM) test cell and a pulsed signal source were introduced in 1997.Although this procedure has many advantages and is easy to understand,measurements show several shortcomings of this calibration method.To overcome the disadvantages of the known systems,a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested.The UHF sensor was placed in a region with minimum distortion of the electric field due to its installation.Experience shows that the new method for calibrating UHF sensors is necessary in order to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections.Due to its surprisingly simple structure,its low price and low overall measurement uncertainty,it is the preferred method for calibrating UHF sensors for GIS applications.
基金Supported by National Natural Science Foundation of China(50707023)
文摘This paper describes a realizable fabrication method to manufacture chemical gas sensors by using singlewalled carbon nanotubes(SWCNTs).The sensors were tested for the monitoring of SF_6 decomposition gas produced by partial discharge(PD) in GIS tank.The results showed a superior sensitivity,favorable reliability and good reproducibility. For further clarifying the relativity between sensor response and partial discharge activity,the discharge in GIS tank was monitored simultaneously through conventional pulse current method and a SWCNTs gas sensor,and the measurement results were put together for comparative analysis in this paper.The sensor response showed a great dependence on partial discharge characteristics.The sensor response increased nearly linearly with limits when the energy of discharge was persistently accumulated.Partial discharge power had a great influence on the response rate and the time delay.With the increase of partial discharge power,the response rate augmented almost in proportion while the time delay gradually becomes shorter with limits.The results were quite favorable to assess the partial discharge intensity and duration to some extent.Compared with pulse current method,the sensor was predominant to detect partial discharge exposed to constantly high levels of noise.It was capable of detecting partial discharge which was too weak to be detected with pulse current method.However,the sensor response didn't show much dependency on the apparent discharge of partial discharge.
文摘An increasing number of large-scale renewable plants are generating abundant electricity. As power-to-gas and power-to-x technologies become promising ways to utilize surplus electricity to enhance the flexibility of energy systems, an innovative gas-electricity integrated transmission system (GEITS) to co-transmit electricity and hydrogen or other gas products is proposed, with the foreseeable advantages of compact structure, lower installation cost, and larger energy capacity. This paper investigates the feasibility of GEITS, suggests a design guideline, and gives the operation technical parameters of GEITS in different application scenarios. The dimensions and operating pressures of GEITS benchmark natural gas pipelines and then the nominal voltages of GEITS are calculated based on the electrical strength of high-pressure hydrogen. The nominal ampacities of GEITS are evaluated by temperature-rising simulations, which are larger than those of other transmission lines. Furthermore, high-pressure flowing hydrogen acting as an electrical insulator is a novel topic, and it is investigated via experimental validation on a scale model. Although the effect of 0.4 m/s flowing hydrogen on discharge characteristics has not been observed compared to static hydrogen, the discharge is impaired in 2.4 m/s flowing nitrogen. Future works will investigate the electrical strength of high-pressure long-distance hydrogen gaps under lightning impulse tests and the discharge phenomenon in higher flowing-velocity hydrogen. Methane and methane blended with hydrogen with higher insulation performance can increase the nominal voltages.
基金Science and Technology Project of State Grid Corporation of China(SGCC),Grant/Award Number:5500-202355794A-3-8-KJ。
文摘CF_(4)is a major decomposition product of the insulating gas in C_(4)F_(7)N-insulated gasinsulated metal-enclosed switchgear(GIS)during partial discharge or overheating faults.Its detection is essential for effective online monitoring and fault diagnosis of GIS.However,the application of photoacoustic spectroscopy for CF_(4)detection is hampered by significant cross-interference from the background C_(4)F_(7)N gas.In this paper,quantum chemical calculations revealed that C_(4)F_(7)N hydrolyses to form perfluoroisobutyrate and ammonia under base catalysis,exhibiting a low reaction energy barrier and high Gibbs free energy change,indicating ease of initiation and substantial reaction extent.This chemical specificity,unlike the stable CF_(4)which does not undergo such a reaction,enables selective purification of the gas to be detected through this hydrolysis reaction.Leveraging this insight,an experimental system was constructed that cascades chemical absorption purification with photoacoustic spectroscopy detection.This system effectively mitigates the cross-interference of C_(4)F_(7)N in CF_(4)detection by selectively absorbing C_(4)F_(7)N with over 95%efficiency through a base-catalysed nucleophilic hydrolysis reaction.This enabled the precise detection of trace amounts of CF_(4)against a substantial background of C_(4)F_(7)N with a detection limit reaching 14.79μL/L.This advancement offers support for the online monitoring and fault diagnosis of eco-friendly GIS.
基金Sichuan Science and Technology Program,Grant/Award Number:2023NSFSC0297。
文摘C_(5)F_(10)O/CO_(2)gas mixture is one of the most promising alternatives to SF_(6)as an insulating gas in high-voltage switchgear.As a key performance index in product design,the temperature rise characteristics are rarely reported.In this paper,the thermodynamic parameters of C_(5)F_(10)O/CO_(2)gas mixture were calculated first.Then,the calculation model of transient temperature rise was constructed for a 252 kV/3150 A bus,and a temperature rise experimental platform was built to verify the reliability of the proposed calculation model.On this basis,the influence of different factors such as load current,charging pressure,mixing ratio,and structure size on the temperature rise of the bus was further analysed,and it is found that increasing the charging pressure and the mixing ratio of C5F10O could effectively reduce the bus temperature rise but it still could not reach the level of SF_(6).The main structure size that affects the temperature rise of the bus is the outer diameter of the conductor,which increases by 10.2%,and the temperature rise is the same as that of the original SF_(6)bus.Finally,a high-precision bus temperature rise surrogate model,which combined with the Latin hypercube model,the coefficient of prognosis,and the Kriging fitting method was established to facilitate the structural design.
基金supported by National Natural Science Foundation of China(No.52107029)China Postdoctoral Science Foundation(No.2021M692599)the Shaanxi Provincial Department of Education Youth Innovation Team Research Plan Project(No.23JP102).
文摘In this paper,we compare the differences in the charge accumulation for two different models about conductivity:one in which the conductivity value of the spacer is invariant with time(steady-state conductivity,ModelⅠ)and one in which the conductivity value can vary dynamically with time(dynamic conductivity,ModelⅡ).The time for the potential distribution to reach a stable state is 8078 s in ModelⅠand 7932 s in ModelⅡ.After the charge accumulation reaches saturation,the charges migrate to the middle of the spacer under the applied electric field.Maximum tangential field strength is 2.56×10^(6)V/m in ModelⅠand 2.84×5 C/m^(3),which is much smaller than the charge density in the spacer.The mechanism underlying the charge accumulation phenomenon is the differences in the conductivity value distribution caused by a time-varying temperature gradient field.This paper can provide a more precise theoretical basis for the selection and modification of HVDC-GIL spacer.
基金supported by the National Natural Science Foundation of China,Grant Number:52377156the State Key Laboratory of Power System Operation and Control,Grant Number:SKLD23KM04the Open Fund of State Key Laboratory of Power Grid Environmental Protection,Grant Number:GYW51202301429.
文摘Perfluoroisobutyronitrile(C_(4)F_(7)N)is recognised as the next-generation dielectric medium for eco-friendly gas-insulated equipment(GIE).However,there is gas metal incompatibility in strong electromagnetic environments and environmentally friendly insulating gas atmospheres that endangers the operational safety and service life of GIE.Here,a solvent-induced grain boundary reconstruction method was proposed to prepare corrosion-resistant copper rapidly.Accordingly,the partial dischargeinduced gas-metal interaction was simulated and the corrosion resistance properties of copper were evaluated.Additionally,the gas-solid interaction mechanism was investigated and the improvement mechanism of the proposed method on the stability of the gas-solid interface was discussed.Related results provide a reference for the development and application reliability of C_(4)F_(7)N-based eco-friendly GIE.
基金Natural Science Foundation of Beijing,Grant/Award Number:3244048National Natural Science Foundation of China,Grant/Award Number:52407175‘Chen Guang’project supported by the Shanghai Municipal Education Commission and the Shanghai Education Development Foundation,Grant/Award Number:21CGA63。
文摘Partial discharge(PD)detection is considered one of the most crucial and effective methods for identifying defects in electrical equipment.Consequently,investigating advanced and efficient PD monitoring techniques is essential for the development of gas-insulated equipment(GIE)and the construction of ultra-high-voltage(UHV)networks.This paper first explores the causes and impact characteristics of various defects in GIE based on experimental results and simulation analysis.It then reviews current research on advanced PD measurement techniques,integrating acoustic,chemical and optical methods.The findings preliminarily demonstrate the unique advantages and applicability of the advanced methods for complex detection environments.Finally,this paper ad-dresses the technical challenges and potential breakthroughs associated with these detection techniques.In this regard,this study aims to provide technical insights and research directions for defect detection techniques in UHV GIE.
基金National Natural Science Foundation of China,Grant/Award Number:52177140Fundamental Research Funds for the Central Universities,Grant/Award Number:2023JC005The State Grid Corporation of China Limited Science and Technology Program,Grant/Award Number:5200-202355792A-3-8-KJ。
文摘Within 30 min after live operation of gas-insulated switchgear(GIS),more than 60%of discharge failures are caused by metallic particles.To address this issue,this study explored the vibration propagation mechanisms in GIS cavities and established an equivalent vibration transmission model.A kinetic energy transfer conservation model between the cavity and particles was constructed,systematically analyzing the critical factors affecting the particle starting field strength and explicitly formulating the criterion for vibration-induced particle activation.The electric field distortion caused by particle rotation was investigated,and a collision dynamics model characterizing rotational mo-tion was developed.By analyzing the critical conditions for stable and rotational motion,the corresponding criterion was derived.The results showed that the electric field distortion caused by flaky particles increases with the rotation angle.Vibration effectively activates particles and enhances their mobility.The discharge risk is positively correlated with vibration intensity and particle thickness,but negatively correlated with particle size.This paper clarifies the motion mechanism of flaky metal particles in GIS under shock vibration,providing support for solving the problem of frequent faults after GIS live operation.
基金Key Program of Joint Funds of the National Natural Science Foundation of China,Grant/Award Number:U22B20118。
文摘Gas-insulated switchgear(GIS)plays a critical role in ensuring the reliability of power systems,but partial discharge(PD)is a primary cause of failures within GIS equipment.Traditional PD diagnostic methods rely heavily on laboratory data,which differ signifi-cantly from that under the complex conditions of field data,leading to a marked drop in recognition accuracy when they are applied to field PD diagnosis.This study addresses the challenge by integrating field data into the training process,utilising a deep transfer learning approach that combines laboratory and field data to improve diagnostic accuracy for GIS PD.The research collected PD data from laboratory models representing five defect types and field data gathered from operational GIS equipment.A deep residual network(ResNet50)was pretrained using laboratory data and fine-tuned with field data through deep transfer learning to optimise the recognition of PD in field conditions.The results show that the proposed model achieves a significantly higher recognition accuracy(93.7%)for field data compared to traditional methods(60%-70%).The integration of deep transfer learning ensures that both low-dimensional general features from labora-tory data and high-dimensional specific features from field data are effectively utilised.This research significantly contributes to improving the diagnostic accuracy of PD in GIS under field conditions,providing a robust method for defect detection in operational equipment.
基金National Engineering Research Center of UHV Technology and New Electrical Equipment Basis of China Southern Power Grid Research Institute Co.,Ltd,Grant/Award Number:NERCUTNEEB-2022-KF-08。
文摘Accurately identifying the location and type of internal defects in gas-insulated switchgear(GIS)is a challenge.To address this challenge,this study proposes a novel method for the nondestructive detection of GIS internal defects.This method is based on x-ray digital radiography(X-DR)technology and an improved real-time models for object detection(RTMdet)algorithm,namely GIS-specific localised internal defect-RTMdet.Firstly,the X-DR images of GIS are preprocessed by dynamic limit adaptive histogram equalisation algorithm to improve the images contrast.Then,a convolution shuffle upsample module for upsampling is proposed,which enlarges the defect feature map by multi-convolution and pixel shuffling,reduces the information loss,and enhances the interaction between the feature information.Finally,both the multi-channel attention net and the global attention mechanism are integrated into the neck network for enhancing local feature extraction and global information association.Experiments demonstrate that the pro-posed method achieves a mean average precision@0.5:0.95 of 94.9%,showcasing excellent overall performance and generalisation ability,and is more suitable for accurate nondestructive detection of internal defects of GIS in complex scenarios.
基金National Key R&D Program of China,Grant/Award Numbers:2022YFB2403700,2022YFB2403705Natural Science Foundation of Chongqing,Grant/Award Number:CSTB2022NSCQ-MSX1247。
文摘Mechanical vibration defect is the key factor leading to sudden failure of gas-insulated switchgear(GIS)equipment.It is important to realise effective prediction of the me-chanical vibration state development trend of GIS equipment in order to improve its active safety protection level.This paper carried out research on the accurate prediction method and experimental validation of the mechanical vibration state and its defect severity development trend for the GIS equipment.Firstly,the deep and shallow vibration feature parameters for different mechanical defect signals were jointly extracted by time-domain features and deep belief network methods.Secondly,a new prediction model,incorporating the attention mechanism and the bidirectional gated recurrent unit(BiGRU),was constructed with the deep and shallow vibration feature parameters as inputs.Finally,the prediction trend effectiveness was verified based on the real-type GIS mechanical simulation platform and the field operation GIS equipment.Results show that the deep and shallow vibration feature extraction method proposed in this paper can characterise the mechanical defect information more comprehensively.The new prediction method of the vibration state trend based on the attention-BiGRU model shows ideal accuracy,and the predicted vibration state development trend is highly consistent with the actual,with an average absolute error of 0.063.The root mean square error(ERMSE)value of the prediction method is<5%,which reduces the relative error value at least 37% compared with the traditional prediction models.This paper provides a valuable reference for the proactive defence of GIS mechanical failure.
