Based on a two-dimensional axisymmetric magneto-hydrodynamic （MHD） model, low current vacuum arc （LCVA） characteristics are studied. The influence of cathode process under different axial magnetic fields and diffe...Based on a two-dimensional axisymmetric magneto-hydrodynamic （MHD） model, low current vacuum arc （LCVA） characteristics are studied. The influence of cathode process under different axial magnetic fields and different anode radii on LCVA characteristics is also simulated. The results show that the influence of both cathode process and anode radii on LCVA is significant. The sign of anode sheath potentials can change from negative to positive with the decrease of anode radii. The simulation results are in part verified by experimental results. Especially, as the effect of ion kinetic energy is considered, ion temperature is improved significantly; which is in agreement with experimental results.展开更多
A high-current vacuum arc （HCVA） with the consideration of anode vapor is modeled and simulated. First, from the HCVA column model, the heat flux density to the anode is obtained, which is put into the anode activit...A high-current vacuum arc （HCVA） with the consideration of anode vapor is modeled and simulated. First, from the HCVA column model, the heat flux density to the anode is obtained, which is put into the anode activity model, and the parameter distributions （such as the vapor temperature and velocity） of anode vapor are obtained from the simulation results of the anode activity model. Then, by iterating and calculating the HCVA column model and anode activity model, the interaction between the HCVA column and the anode vapor is simulated and analyzed. In the simulation, the distribution of the axial magnetic field （AMF） generated by the electrode system is calculated by software ANSYS. The simulation results show that the influence of anode vapor on the parameter distributions in the arc column is significant. The simulation results are also compared with the vacuum arc photograph.展开更多
In this study, the influence of the initial jet angles （IJAs） and ion number densities （INDs） at the cathode side on the low current vacuum arc （LCVA） characteristics is simulated and analysed. The results show ...In this study, the influence of the initial jet angles （IJAs） and ion number densities （INDs） at the cathode side on the low current vacuum arc （LCVA） characteristics is simulated and analysed. The results show that the ion temperature, electron temperature, ion number density, axial current density and plasma pressure all decrease with the increase of the cathode IJAs. It is also shown that LCVA can cause a current constriction for lower cathode IND, and the anode sheath potential is more nonuniform, which is mainly related to the nonuniform distribution of the axial current density at the anode side.展开更多
The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity,which are strongly influenced by molten pool profile that is influenced by VAR process.To better understan...The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity,which are strongly influenced by molten pool profile that is influenced by VAR process.To better understand the effect of remelting current on molten pool profile of titanium alloy ingot during VAR process,a 3D finite element model is developed by the ANSYS software.The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA.The molten pool depth increases gradually from 30 to 320 s,then the change of molten pool depth is very small during the steady state stage from 320 to 386 s,and lastly the molten pool depth becomes shallow after 386 s.The melting rate and temperature of superheat increase with the remelting current increasing,which leads to the augment of molten pool volume.In the end,the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA.展开更多
The preliminary design of an arc chamber in the 550 kV SF6 circuit breaker was proposed in accordance with the technicai requirements and design experience. The structural optimization was carried out according to the...The preliminary design of an arc chamber in the 550 kV SF6 circuit breaker was proposed in accordance with the technicai requirements and design experience. The structural optimization was carried out according to the no-load flow field simulation results and verified by no-load pressure measurement. Based on load simulation results such as temperature field variation at the arc area and the tendency of post arc current under different recovery voltage, the second optimal design was completed and its correctness was certificated by a breaking test. Results demonstrate that the interrupting capacity of an arc chamber can be evaluated by the comparison of the gas medium recovery speed and post arc current growth rate.展开更多
A new methodology for the detection and identification of insulator arc faults for the smart grid environment based on phasor angle measurements is presented in this study and the real time phase angle data are collec...A new methodology for the detection and identification of insulator arc faults for the smart grid environment based on phasor angle measurements is presented in this study and the real time phase angle data are collected using Phasor Measurement Units (PMU). Detection of insulator arcing faults is based on feature extraction and frequency component analysis. The proposed methodology pertains to the identification of various stages of insulator arcing faults in transmission lines network based on leakage current, frequency characteristics and synchronous phasor measurements of voltage. The methodology is evaluated for IEEE 14 standard bus system by modeling the PMU and insulator arc faults using MATLAB/Simulink. The classification of insulator arcs is done using Support Vector Machine (SVM) technique to avoid empirical risk. The proposed methodology using phasor angle measurements employing PMU is used for fault detection/classification of insulator arcing which further helps in efficient protection of the system and its stable operation. In addition, the methodology is suitable for wide area condition monitoring of smart grid rather than end to end transmission lines.展开更多
基于强迫换流原理的混合型直流真空断路器(hybrid direct current vacuum circuit breaker,HDCVCB)是直流开断技术的有效方式之一,其参数设计及开断能力决定于真空灭弧室的特性。介绍了混合型直流真空断路器的典型拓扑结构及其工作原理...基于强迫换流原理的混合型直流真空断路器(hybrid direct current vacuum circuit breaker,HDCVCB)是直流开断技术的有效方式之一,其参数设计及开断能力决定于真空灭弧室的特性。介绍了混合型直流真空断路器的典型拓扑结构及其工作原理,对真空电弧理论和真空灭弧室触头结构的研究概况进行了阐述。分析了直流分断中电流波形与交流中的正弦波不同、电流下降率大、燃弧时间可控等特点,得到了其分断能力与换流电流投入时电弧形态和电极状态密切相关的结论。对不同触头结构下的真空电弧形态演化规律,不同条件下的真空灭弧室的强迫换流分断特性与介质恢复规律等实验研究工作进行了综述,最后对直流真空灭弧室的研发进行了展望。展开更多
断路器的弧后电流是断路器开断性能的重要参量,为了获取高精度、低干扰的弧后电流,本文提出了一种基于真空开关、转移电阻、保护间隙和高精度电流传感器构成的弧后电流测量方法,其中真空开关负责导通大电流,在电流过零前电流转移到转移...断路器的弧后电流是断路器开断性能的重要参量,为了获取高精度、低干扰的弧后电流,本文提出了一种基于真空开关、转移电阻、保护间隙和高精度电流传感器构成的弧后电流测量方法,其中真空开关负责导通大电流,在电流过零前电流转移到转移电阻上,然后利用高精度电流传感器间接测量弧后电流。建立了弧后电流装置的电流转移过程模型,分析了电流转移完成时刻和转移电流峰值受转移电阻、电流大小和真空开关刚分时刻的影响。基于仿真得到弧后电流测量装置的参数,设计了弧后电流测量装置样机,对转移电阻进行了特殊无感设计并与保护间隙实现配合保护。最后进行了10 k V真空断路器在合成回路试验中的弧后电流测量,在开断5 k A电流时,弧后电流峰值为500 m A左右,脉宽5μs,弧后测量干扰小,波形平滑。对比试验结果和前人研究成果,验证了基于电流转移原理的弧后电流测量装置的可行性和准确性。展开更多
基金National Natural Science Foundation of China (No.50537050)the Innovation Foundation of State Key Laboratory of Electrical Insulation and Power Equipment
文摘Based on a two-dimensional axisymmetric magneto-hydrodynamic （MHD） model, low current vacuum arc （LCVA） characteristics are studied. The influence of cathode process under different axial magnetic fields and different anode radii on LCVA characteristics is also simulated. The results show that the influence of both cathode process and anode radii on LCVA is significant. The sign of anode sheath potentials can change from negative to positive with the decrease of anode radii. The simulation results are in part verified by experimental results. Especially, as the effect of ion kinetic energy is considered, ion temperature is improved significantly; which is in agreement with experimental results.
基金supported by National Natural Science Foundation of China (No. 50907045)
文摘A high-current vacuum arc （HCVA） with the consideration of anode vapor is modeled and simulated. First, from the HCVA column model, the heat flux density to the anode is obtained, which is put into the anode activity model, and the parameter distributions （such as the vapor temperature and velocity） of anode vapor are obtained from the simulation results of the anode activity model. Then, by iterating and calculating the HCVA column model and anode activity model, the interaction between the HCVA column and the anode vapor is simulated and analyzed. In the simulation, the distribution of the axial magnetic field （AMF） generated by the electrode system is calculated by software ANSYS. The simulation results show that the influence of anode vapor on the parameter distributions in the arc column is significant. The simulation results are also compared with the vacuum arc photograph.
基金National Natural Science Foundation of China(No.50537050)
文摘In this study, the influence of the initial jet angles （IJAs） and ion number densities （INDs） at the cathode side on the low current vacuum arc （LCVA） characteristics is simulated and analysed. The results show that the ion temperature, electron temperature, ion number density, axial current density and plasma pressure all decrease with the increase of the cathode IJAs. It is also shown that LCVA can cause a current constriction for lower cathode IND, and the anode sheath potential is more nonuniform, which is mainly related to the nonuniform distribution of the axial current density at the anode side.
基金the National Basic Research Program(973) of China (No.2007CB613802)
文摘The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity,which are strongly influenced by molten pool profile that is influenced by VAR process.To better understand the effect of remelting current on molten pool profile of titanium alloy ingot during VAR process,a 3D finite element model is developed by the ANSYS software.The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA.The molten pool depth increases gradually from 30 to 320 s,then the change of molten pool depth is very small during the steady state stage from 320 to 386 s,and lastly the molten pool depth becomes shallow after 386 s.The melting rate and temperature of superheat increase with the remelting current increasing,which leads to the augment of molten pool volume.In the end,the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA.
文摘The preliminary design of an arc chamber in the 550 kV SF6 circuit breaker was proposed in accordance with the technicai requirements and design experience. The structural optimization was carried out according to the no-load flow field simulation results and verified by no-load pressure measurement. Based on load simulation results such as temperature field variation at the arc area and the tendency of post arc current under different recovery voltage, the second optimal design was completed and its correctness was certificated by a breaking test. Results demonstrate that the interrupting capacity of an arc chamber can be evaluated by the comparison of the gas medium recovery speed and post arc current growth rate.
文摘A new methodology for the detection and identification of insulator arc faults for the smart grid environment based on phasor angle measurements is presented in this study and the real time phase angle data are collected using Phasor Measurement Units (PMU). Detection of insulator arcing faults is based on feature extraction and frequency component analysis. The proposed methodology pertains to the identification of various stages of insulator arcing faults in transmission lines network based on leakage current, frequency characteristics and synchronous phasor measurements of voltage. The methodology is evaluated for IEEE 14 standard bus system by modeling the PMU and insulator arc faults using MATLAB/Simulink. The classification of insulator arcs is done using Support Vector Machine (SVM) technique to avoid empirical risk. The proposed methodology using phasor angle measurements employing PMU is used for fault detection/classification of insulator arcing which further helps in efficient protection of the system and its stable operation. In addition, the methodology is suitable for wide area condition monitoring of smart grid rather than end to end transmission lines.
文摘基于强迫换流原理的混合型直流真空断路器(hybrid direct current vacuum circuit breaker,HDCVCB)是直流开断技术的有效方式之一,其参数设计及开断能力决定于真空灭弧室的特性。介绍了混合型直流真空断路器的典型拓扑结构及其工作原理,对真空电弧理论和真空灭弧室触头结构的研究概况进行了阐述。分析了直流分断中电流波形与交流中的正弦波不同、电流下降率大、燃弧时间可控等特点,得到了其分断能力与换流电流投入时电弧形态和电极状态密切相关的结论。对不同触头结构下的真空电弧形态演化规律,不同条件下的真空灭弧室的强迫换流分断特性与介质恢复规律等实验研究工作进行了综述,最后对直流真空灭弧室的研发进行了展望。
文摘断路器的弧后电流是断路器开断性能的重要参量,为了获取高精度、低干扰的弧后电流,本文提出了一种基于真空开关、转移电阻、保护间隙和高精度电流传感器构成的弧后电流测量方法,其中真空开关负责导通大电流,在电流过零前电流转移到转移电阻上,然后利用高精度电流传感器间接测量弧后电流。建立了弧后电流装置的电流转移过程模型,分析了电流转移完成时刻和转移电流峰值受转移电阻、电流大小和真空开关刚分时刻的影响。基于仿真得到弧后电流测量装置的参数,设计了弧后电流测量装置样机,对转移电阻进行了特殊无感设计并与保护间隙实现配合保护。最后进行了10 k V真空断路器在合成回路试验中的弧后电流测量,在开断5 k A电流时,弧后电流峰值为500 m A左右,脉宽5μs,弧后测量干扰小,波形平滑。对比试验结果和前人研究成果,验证了基于电流转移原理的弧后电流测量装置的可行性和准确性。
