The corrosion resistance of aluminum(Al)cable-copper(Cu)terminal joints fabricated by magnetic pulse crimping(MPC)and hydraulic clamp crimping(HCC)was compared.Performance degradation was evaluated by mechanical and e...The corrosion resistance of aluminum(Al)cable-copper(Cu)terminal joints fabricated by magnetic pulse crimping(MPC)and hydraulic clamp crimping(HCC)was compared.Performance degradation was evaluated by mechanical and electrical properties.Additionally,corrosion behavior was analyzed by electrochemical testing.Microscopic characterization was performed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).Results show that the tensile strength of the corroded joints is reduced.However,due to the advantages of high-speed forming and contact tightness unique to MPC,the contact resistance of the corroded joints still maintains excellent.Electrochemical tests demonstrate that the MPC joints have higher corrosion potentials and smaller corrosion currents,providing better corrosion resistance.The formation of a primary battery between Al and Cu at the lap joint leads to the formation of severer corrosion pits.展开更多
Permanent faults in medium-voltage cable joints significantly impact the reliability of distribution networks.Radial breakdowns caused by water ingress often lead to several self-extinguishing arc discharges—referred...Permanent faults in medium-voltage cable joints significantly impact the reliability of distribution networks.Radial breakdowns caused by water ingress often lead to several self-extinguishing arc discharges—referred to as incipient faults—before developing into permanent faults.Effective monitoring of incipient faults can help reduce outage costs associated with permanent faults.However,the specific fault scenarios of incipient faults remain insufficiently understood.To address this gap,this study designed a simulation experiment replicating incipient fault conditions in medium-voltage cable joints under humid environments,based on actual operating scenarios.The experiment compared the insulation strength required to trigger incipient faults and examined both non-electrical fault characteristics,such as insulation damage and arc flame intensity,and electrical characteristics,such as fault current and impedance.Experimental observations show that,in cable joints,gaps without accumulated water retain sufficient insulation strength to prevent breakdown.However,the infiltration of accumulated water shortens the effective insulation path,thereby lowering the breakdown threshold.The peak current of an incipient fault can range from hundreds to thousands of amperes,with a duration of approximately 1/8 to 1/4 of a power–frequency cycle.During incipient faults,arc burning on the pore wall leaves conductive traces,which progressively reduce the insulation strength of the surrounding environment.As these traces accumulate over multiple events,the likelihood of breakdown increases,ultimately resulting in a permanent fault.Permanent faults are characterized by intense,sustained arc discharges that persist over a macroscopic time scale and exhibit flat-shoulder waveforms within individual cycles,with discharge intensity increasing progressively over time.展开更多
The oscillating voltage test is a nondestructive detection method for partial discharge of XLPE （cross linked polyethylene） cable and has been applied recently. This paper made three kinds of varying severity artifi...The oscillating voltage test is a nondestructive detection method for partial discharge of XLPE （cross linked polyethylene） cable and has been applied recently. This paper made three kinds of varying severity artificial defect models of cable joints in 10 kV XLPE cable. Oscillating voltage is applied to the model, by use of pulse current method to detect partial discharge signals. In order to study the statistical characteristics of partial discharge of cable joint under the oscillating voltage, three-dimensional statistical map has been made. The results show that for the same kind of defects, with the increases of the defect severity, the discharge interval extended, the magnitude and the number of partial discharge increase, for different kinds of defects, obvious differences exist among the maps, this may established a foundation for the further study of the partial discharge pattern recognition of XLPE cable under oscillating voltage.展开更多
Charge dynamics at interfaces in high voltage direct current(HVDC)cable joints consisting of cable,joint insulation and lubricant may have an impact on the overall joint reliability.Although interactions between diffe...Charge dynamics at interfaces in high voltage direct current(HVDC)cable joints consisting of cable,joint insulation and lubricant may have an impact on the overall joint reliability.Although interactions between different lubricants and the joint insulation have been studied in recent years,the effect of lubricant diffusion on the electrical properties and charge dynamics at interfaces remains unclear and is therefore investigated in this paper.Different lubricants were applied at the interface of crosslinked polyethylene(XLPE)and silicone rubber(SIR)samples,and mass,electrical conductivity,and space charge were measured over a 96 h ageing period.The mass of the samples was found to exhibit nonmonotonic behaviour,indicating complex interactions between the lubricant and material.XLPE experiences a decrease in conductivity while there is an increase in conductivity for SIR,which is linked to the migration of lubricant and therefore changes in trap distribution.Space charge measurements indicate changes in trap characteristics,which depend strongly on the used type of lubricant.The findings highlight that lubricant diffusion affects both the bulk properties and charge accumulation at the interface,and underline the large effect of the type of lubricant.These results are crucial for understanding the long-term performance of cable joints and insulating materials in HVDC cable systems.展开更多
In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that ea...In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that each strand of the cable inside the joint is able to come to the outermost by transposition. This paper presents analysis, calculation and figures for the strand transposition. According to the twist procedures of the superconducting cable, the author computed the actual pitch of each stage cable, consecutively computed the projection of each stage cable on the axis of the cable (z axis) and the corresponding twist angle as the z coordinate changes, which is then drawn by AutoCAD. From the results shown in the figures, the minimal cable length, which enables each strand to transpose almost equally to the outermost of the cable in such a length, call be determined as the optimal joint length.展开更多
The integration of REBCO superconducting coils into compact tokamak toroidal field magnets represents a transformative advancement in fusion technology.In the fabrication of these magnets,electrical connections betwee...The integration of REBCO superconducting coils into compact tokamak toroidal field magnets represents a transformative advancement in fusion technology.In the fabrication of these magnets,electrical connections between pancake coils are typically established through a transverse bridging joint,the performance of which critically impacts device efficiency.To address the demand for enhanced connectivity,this study presents a novel bridge-type"stacked joint"utilizing a superconducting-copper composite structure,optimized for inter-coil connections of stacked REBCO cables.Leveraging a modular stacking approach and low-temperature soldering,this design achieves a resistance as low as 1 nΩover a 10 cm length alongside a soldering resistivity below 25 nΩcm^(2)in a liquid nitrogen(77 K)self-field environment.The study further investigates the impact of tape length and quantity on joint electrical performance under this configuration.Rigorous testing,including 10 thermal cycles(77 K to room temperature)and pressure loads up to 30 MPa,confirms the joint’s structural reliability and the consistency of the fabrication process,underscoring its potential for fusion applications.展开更多
基金supported by the National Natural Science Foundation of China (No.52175315)the Shenzhen Science and Technology Program,China (No.KQTD20200820113110016)the Hunan Provincial Postgraduate Research Innovation Program,China (No.CX20220404)。
文摘The corrosion resistance of aluminum(Al)cable-copper(Cu)terminal joints fabricated by magnetic pulse crimping(MPC)and hydraulic clamp crimping(HCC)was compared.Performance degradation was evaluated by mechanical and electrical properties.Additionally,corrosion behavior was analyzed by electrochemical testing.Microscopic characterization was performed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).Results show that the tensile strength of the corroded joints is reduced.However,due to the advantages of high-speed forming and contact tightness unique to MPC,the contact resistance of the corroded joints still maintains excellent.Electrochemical tests demonstrate that the MPC joints have higher corrosion potentials and smaller corrosion currents,providing better corrosion resistance.The formation of a primary battery between Al and Cu at the lap joint leads to the formation of severer corrosion pits.
基金supported by National Natural Science Foundation of China(No.52077133).
文摘Permanent faults in medium-voltage cable joints significantly impact the reliability of distribution networks.Radial breakdowns caused by water ingress often lead to several self-extinguishing arc discharges—referred to as incipient faults—before developing into permanent faults.Effective monitoring of incipient faults can help reduce outage costs associated with permanent faults.However,the specific fault scenarios of incipient faults remain insufficiently understood.To address this gap,this study designed a simulation experiment replicating incipient fault conditions in medium-voltage cable joints under humid environments,based on actual operating scenarios.The experiment compared the insulation strength required to trigger incipient faults and examined both non-electrical fault characteristics,such as insulation damage and arc flame intensity,and electrical characteristics,such as fault current and impedance.Experimental observations show that,in cable joints,gaps without accumulated water retain sufficient insulation strength to prevent breakdown.However,the infiltration of accumulated water shortens the effective insulation path,thereby lowering the breakdown threshold.The peak current of an incipient fault can range from hundreds to thousands of amperes,with a duration of approximately 1/8 to 1/4 of a power–frequency cycle.During incipient faults,arc burning on the pore wall leaves conductive traces,which progressively reduce the insulation strength of the surrounding environment.As these traces accumulate over multiple events,the likelihood of breakdown increases,ultimately resulting in a permanent fault.Permanent faults are characterized by intense,sustained arc discharges that persist over a macroscopic time scale and exhibit flat-shoulder waveforms within individual cycles,with discharge intensity increasing progressively over time.
文摘The oscillating voltage test is a nondestructive detection method for partial discharge of XLPE （cross linked polyethylene） cable and has been applied recently. This paper made three kinds of varying severity artificial defect models of cable joints in 10 kV XLPE cable. Oscillating voltage is applied to the model, by use of pulse current method to detect partial discharge signals. In order to study the statistical characteristics of partial discharge of cable joint under the oscillating voltage, three-dimensional statistical map has been made. The results show that for the same kind of defects, with the increases of the defect severity, the discharge interval extended, the magnitude and the number of partial discharge increase, for different kinds of defects, obvious differences exist among the maps, this may established a foundation for the further study of the partial discharge pattern recognition of XLPE cable under oscillating voltage.
文摘Charge dynamics at interfaces in high voltage direct current(HVDC)cable joints consisting of cable,joint insulation and lubricant may have an impact on the overall joint reliability.Although interactions between different lubricants and the joint insulation have been studied in recent years,the effect of lubricant diffusion on the electrical properties and charge dynamics at interfaces remains unclear and is therefore investigated in this paper.Different lubricants were applied at the interface of crosslinked polyethylene(XLPE)and silicone rubber(SIR)samples,and mass,electrical conductivity,and space charge were measured over a 96 h ageing period.The mass of the samples was found to exhibit nonmonotonic behaviour,indicating complex interactions between the lubricant and material.XLPE experiences a decrease in conductivity while there is an increase in conductivity for SIR,which is linked to the migration of lubricant and therefore changes in trap distribution.Space charge measurements indicate changes in trap characteristics,which depend strongly on the used type of lubricant.The findings highlight that lubricant diffusion affects both the bulk properties and charge accumulation at the interface,and underline the large effect of the type of lubricant.These results are crucial for understanding the long-term performance of cable joints and insulating materials in HVDC cable systems.
文摘In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that each strand of the cable inside the joint is able to come to the outermost by transposition. This paper presents analysis, calculation and figures for the strand transposition. According to the twist procedures of the superconducting cable, the author computed the actual pitch of each stage cable, consecutively computed the projection of each stage cable on the axis of the cable (z axis) and the corresponding twist angle as the z coordinate changes, which is then drawn by AutoCAD. From the results shown in the figures, the minimal cable length, which enables each strand to transpose almost equally to the outermost of the cable in such a length, call be determined as the optimal joint length.
基金National MCF Energy R&D Program under Grant 2022YFE03150103in part by CTRFR project(Compact-Tokamak based repetitive Reconnection-heated Fusion Reactor)from Shaanxi Startorus Fusion Technology Co.,Ltd.
文摘The integration of REBCO superconducting coils into compact tokamak toroidal field magnets represents a transformative advancement in fusion technology.In the fabrication of these magnets,electrical connections between pancake coils are typically established through a transverse bridging joint,the performance of which critically impacts device efficiency.To address the demand for enhanced connectivity,this study presents a novel bridge-type"stacked joint"utilizing a superconducting-copper composite structure,optimized for inter-coil connections of stacked REBCO cables.Leveraging a modular stacking approach and low-temperature soldering,this design achieves a resistance as low as 1 nΩover a 10 cm length alongside a soldering resistivity below 25 nΩcm^(2)in a liquid nitrogen(77 K)self-field environment.The study further investigates the impact of tape length and quantity on joint electrical performance under this configuration.Rigorous testing,including 10 thermal cycles(77 K to room temperature)and pressure loads up to 30 MPa,confirms the joint’s structural reliability and the consistency of the fabrication process,underscoring its potential for fusion applications.
