Arc flashes pose significant hazards to personnel working with energised power lines due to their high thermal risk,quantified by incident energy(IE)in joules or calories per area.Accurate estimation of IE is crucial ...Arc flashes pose significant hazards to personnel working with energised power lines due to their high thermal risk,quantified by incident energy(IE)in joules or calories per area.Accurate estimation of IE is crucial for ensuring safety.The most widely employed method for estimating IE from an arc flash is outlined in IEEE Std 1584-2018,which applies exclusively to three-phase AC arc flashes.However,limited research has explored alternative methods due to the complexities,costs,and preparation involved.Numerical simulations offer a viable alternative for studying arc flashes.This paper introduces a multiphysics simulation approach for determining IE by modelling three-phase AC arc flashes using the magnetohydrodynamics(MHD)theory.This study exclusively investigates horizontal electrodes in open-air(HOA)configuration due to the specific characteristics of the local power system configuration,which predominantly features overhead power lines,and the available test setup in the laboratory.The IE derived from simulations is compared with measurements from an arc flash laboratory based on IEEE Std 1584-2018 and with the IE calculated by the standard itself.The results indicate a significant alignment between this innovative approach and other methods for estimating IE for three-phase arc flashes.展开更多
This paper focuses on the energisation of high voltage DC(HVDC)and medium voltage DC(MVDC)insulation systems,referring mainly to cables for both theoretical development and validation testing.Cable system energisation...This paper focuses on the energisation of high voltage DC(HVDC)and medium voltage DC(MVDC)insulation systems,referring mainly to cables for both theoretical development and validation testing.Cable system energisation can be frequent during its lifetime,and it can possibly be affected by partial discharges(PD),because of manufacturing,laying,ageing,interfaces or structural cavities(as butt gaps).A theory-driven and measurement-based procedure is presented in this paper,having the purpose to minimise PD inception risk.This procedure is based on stepwise voltage application during cable energisation.The fundamental idea behind the proposed approach stems from considering that the jump voltage is the trigger of PD occurrence.Indeed,the jump voltage,and the consequent electric field variation,directly relates to AC PD inception voltage(PDIVAC).In addition,the electric field distribution in an insulation system is driven by insulation permittivity(capacitance)during voltage transients,and by conductivity in DC,thus the PDIVAC is generally smaller than DC PD inception voltage(PDIVDC).Hence,energising a DC cable by an initial step lower than PDIVAC,and then increasing the voltage in steps smaller than PDIVAC,would minimise the risk of PD inception during transients and the relevant degradation rate.However,this does not change,the risk of occurrence(if any)of low-repetition partial discharges at DC steady state.Effectiveness of the proposed technique is proved by the help of tests performed on cables with artificial surface and internal defects.It is shown that compared with the conventional energisation consisting of rapidly increasing voltage,the stepwise approach can reduce the risk of PD inception and related extrinsic ageing,even for the steady state voltages larger than PDIVDC.展开更多
A superconducting magnet(SM)can produce high magnetic fields up to a dozen times stronger than those generated by an electromagnet made of normal conductors or a permanent magnet(PM),and thus has attracted increasing ...A superconducting magnet(SM)can produce high magnetic fields up to a dozen times stronger than those generated by an electromagnet made of normal conductors or a permanent magnet(PM),and thus has attracted increasing research efforts in many domains including medical devices,large scientific equipment,transport,energy storage,power systems,and electric machines.Wireless energisers,e.g.,high temperature superconducting(HTS)flux pumps,can eliminate the thermal load from current leads and arc erosion of slip rings,and are thus considered a promising energisation tool for SMs.However,the time‐averaged DC output voltage in existing HTS flux pumps is generated by dynamic resistance:the dynamic loss is unavoidable,and the total AC loss will become significant at high frequencies.This study introduces a highly efficient superconducting wireless energizer(SWE)designed specifically for SMs.The SWE takes advantage of the inherent properties of a superconducting loop,including flux conservation and zero DC resistivity.Extensive theoretical analysis,numerical modelling exploiting the H‐ϕformulation,and experimental measurements were conducted to demonstrate the efficiency and efficacy of the novel SWE design.The electromechanical performance and loss characteristics of the SWE system have also been investigated.Compared to conventional HTS flux pumps,the proposed SWE has lower excitation loss,in the order of 10−1 mW,and thus can achieve a high system efficiency of no less than 95%.Furthermore,it has a simpler structure with higher reliability,considered ready for further industrial development.In addition to deepening the understating of the intricate electromechanical dynamics between magnetic dipoles and superconducting circuits,this article provides a novel wireless energisation technique for SMs and opens the way to step changes in future electric transport and energy sectors.展开更多
基金CPFL Group,Grant/Award Number:PD-00396-3104/2024Federal University of Santa Maria+3 种基金Electrical Engineering Graduate Program of UFSMNational Institute of Science and Technology—Distributed GenerationSmart Grids Institute of UFSMCoordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brazil—Financing Code 001。
文摘Arc flashes pose significant hazards to personnel working with energised power lines due to their high thermal risk,quantified by incident energy(IE)in joules or calories per area.Accurate estimation of IE is crucial for ensuring safety.The most widely employed method for estimating IE from an arc flash is outlined in IEEE Std 1584-2018,which applies exclusively to three-phase AC arc flashes.However,limited research has explored alternative methods due to the complexities,costs,and preparation involved.Numerical simulations offer a viable alternative for studying arc flashes.This paper introduces a multiphysics simulation approach for determining IE by modelling three-phase AC arc flashes using the magnetohydrodynamics(MHD)theory.This study exclusively investigates horizontal electrodes in open-air(HOA)configuration due to the specific characteristics of the local power system configuration,which predominantly features overhead power lines,and the available test setup in the laboratory.The IE derived from simulations is compared with measurements from an arc flash laboratory based on IEEE Std 1584-2018 and with the IE calculated by the standard itself.The results indicate a significant alignment between this innovative approach and other methods for estimating IE for three-phase arc flashes.
文摘This paper focuses on the energisation of high voltage DC(HVDC)and medium voltage DC(MVDC)insulation systems,referring mainly to cables for both theoretical development and validation testing.Cable system energisation can be frequent during its lifetime,and it can possibly be affected by partial discharges(PD),because of manufacturing,laying,ageing,interfaces or structural cavities(as butt gaps).A theory-driven and measurement-based procedure is presented in this paper,having the purpose to minimise PD inception risk.This procedure is based on stepwise voltage application during cable energisation.The fundamental idea behind the proposed approach stems from considering that the jump voltage is the trigger of PD occurrence.Indeed,the jump voltage,and the consequent electric field variation,directly relates to AC PD inception voltage(PDIVAC).In addition,the electric field distribution in an insulation system is driven by insulation permittivity(capacitance)during voltage transients,and by conductivity in DC,thus the PDIVAC is generally smaller than DC PD inception voltage(PDIVDC).Hence,energising a DC cable by an initial step lower than PDIVAC,and then increasing the voltage in steps smaller than PDIVAC,would minimise the risk of PD inception during transients and the relevant degradation rate.However,this does not change,the risk of occurrence(if any)of low-repetition partial discharges at DC steady state.Effectiveness of the proposed technique is proved by the help of tests performed on cables with artificial surface and internal defects.It is shown that compared with the conventional energisation consisting of rapidly increasing voltage,the stepwise approach can reduce the risk of PD inception and related extrinsic ageing,even for the steady state voltages larger than PDIVDC.
文摘A superconducting magnet(SM)can produce high magnetic fields up to a dozen times stronger than those generated by an electromagnet made of normal conductors or a permanent magnet(PM),and thus has attracted increasing research efforts in many domains including medical devices,large scientific equipment,transport,energy storage,power systems,and electric machines.Wireless energisers,e.g.,high temperature superconducting(HTS)flux pumps,can eliminate the thermal load from current leads and arc erosion of slip rings,and are thus considered a promising energisation tool for SMs.However,the time‐averaged DC output voltage in existing HTS flux pumps is generated by dynamic resistance:the dynamic loss is unavoidable,and the total AC loss will become significant at high frequencies.This study introduces a highly efficient superconducting wireless energizer(SWE)designed specifically for SMs.The SWE takes advantage of the inherent properties of a superconducting loop,including flux conservation and zero DC resistivity.Extensive theoretical analysis,numerical modelling exploiting the H‐ϕformulation,and experimental measurements were conducted to demonstrate the efficiency and efficacy of the novel SWE design.The electromechanical performance and loss characteristics of the SWE system have also been investigated.Compared to conventional HTS flux pumps,the proposed SWE has lower excitation loss,in the order of 10−1 mW,and thus can achieve a high system efficiency of no less than 95%.Furthermore,it has a simpler structure with higher reliability,considered ready for further industrial development.In addition to deepening the understating of the intricate electromechanical dynamics between magnetic dipoles and superconducting circuits,this article provides a novel wireless energisation technique for SMs and opens the way to step changes in future electric transport and energy sectors.
