Search

Using laser shadowgraphy and interferometry on a Qin-1 facility, the initial plasma formation and dynamics of an exploding stainless steel liner were investigated. To obtain the absolute electron density distribution inside the liner, we established continuous wave laser interferometry using a streak camera to measure the shift in the fringes over time. Plasma is generated at the interior wall and flows toward the center with a velocity of ∼100 km/s, thus forming a column with higher density by accumulation. Simultaneously, a high-density plasma layer is formed near the interior surface and this layer flows toward the center at approximately 10 km/s. In addition, magnetohydrodynamics (MHD) instabilities were observed at the exterior surface using side-on laser shadow images at a much later time (∼400 ns). The growth in the amplitude and the wavelength of the perturbations were then analyzed. An MHD simulation of this process was then established to demonstrate that the high-density plasma layer carries part of the current and that it flows within the 10 km/s range after comparison with the experimental results. Finally, we measured the voltage and derived the change in the inductance. The results prove that part of the current flows through the center plasma column, which then influences the subsequent plasma flow. [ABSTRACT FROM AUTHOR]

A two-dimensional magneto-hydrodynamic (MHD) model of an ablation-dominated capillary discharge is developed. Special attention is paid to the interaction between the plasma and the capillary in two-dimensional geometry. The mass exchange process is taken into account by adopting a kinetic ablation model and a revised deposition model. The momentum and energy exchange processes associated with the ablated and deposited mass are also considered. By solving this model, key plasma parameters are calculated and presented in the paper. It is shown that distinct two-dimensional features exist in the distribution of these plasma parameters. Further, the calculated temperature results are consistent with previously presented measurements [ABSTRACT FROM AUTHOR]

The air circuit breaker (ACB) is required to switch off the short current at various frequencies in the permanent magnet wind power generation system. The movable contact of ACB consists of multiple parallel contacts, and the arc will be ignited when the short-circuit current appears. This paper focuses on the effect of frequency on arc motion in multiple parallel contacts’ system. A 3-D magnetohydrodynamic (MHD) model of a multiple parallel contacts’ structure is built. In this model, the anode consists of five parallel contacts. The difference in voltage between the near-anode layer and the near-cathode layer is considered. The nonlinear B–H curve of the splitter plate is taken into account. The time-varying electromagnetic field induced by the current loop including electrodes and arc column is calculated. The arc evolution process and effect of frequency on arc motion in multiple parallel contacts’ system are analyzed by the arc voltage and the current density distribution. This paper is expected to provide the theoretical references for the optimal design of arc quenching chamber of ACBs. [ABSTRACT FROM AUTHOR]

Air circuit breaker (ACB) is widely used in power distribution system. The movable contact of ACB consists of multiple parallel contacts and the arc will be ignited between arcing contact and static contact when the short-circuit current appears. This paper focuses on the arc evolution process at various currents in multiple parallel contact systems. A 3-D magnetohydrodynamic model of a multiple parallel contact structures is developed. In this model, the anode consists to five parallel contacts, and they are separated by insulation material. The near-electrode layer with a nonlinear voltage–current density characteristic is modeled to describe the near-electrode voltage drop, and the difference between near-anode and near-cathode layers is considered. The magnetic vector potential approach is adopted to calculate the time-varying electromagnetic field produced by the current loop. The arc evolution processes at various currents are analyzed by current density and arc voltage. It is noted that the anode arc root appears on multiple contacts with the increase of current. The arc evolution process mainly depends on the arc resistance characteristic. [ABSTRACT FROM AUTHOR]

Paralleled high-voltage SF6 circuit breakers with a highly coupled split reactor (HCSR) could realize the function of automatic current-sharing and current-limiting. Aiming at investigating the arc characteristics of paralleled SF6 circuit breakers with an HCSR, the single-phase tests for the paralleled high-voltage SF6 circuit breakers with an HCSR were carried out, including the opening and closing–opening operations. The influence of the capacitor paralleled to one of the breaks was studied. A mathematical model was developed for the paralleled high-voltage SF6 circuit breakers with an HCSR by coupling the equivalent circuit equations into the magnetohydrodynamic (MHD) arc model through the embedded codes, laying the foundation for the further research. The variation of the short-circuit currents in the branches during the breaking process was analyzed in detail. The current-sharing and current-limiting effects are quite satisfying. The temperature distribution of both arc chambers was presented. The calculated results were in agreement with the experimental results to some extent. [ABSTRACT FROM PUBLISHER]

Studies of circuit breakers are of interest to high voltage direct current (HVDC) power system. The method for investigation of the switching arc characteristics of a 500 kV metallic return transfer breaker (MRTB) is presented in this paper, by coupling magneto-hydro-dynamics (MHD) arc model with the resonant circuit equations. 2-D MHD arc model taking account of important physical processes of mass flow, Ohmic heating, radiation energy transfer, momentum exchange, Lorentz force and current flow is developed, and then the influence of stray resistor is analyzed under the interrupting current of DC 4 kA. Calculation results of the distribution of temperature and gas pressure in the nozzle region are presented, where the shock wave and negative voltage-current characteristic of arc are discussed. The calculated arc current and voltage are in agreement with the experimental results to some extent, which could verify the validity of the calculation method partially. [ABSTRACT FROM AUTHOR]

A study was carried out on the characteristics of the dielectric strength of gaseous working medium in a puffer circuit breaker following current interruption. A reduced critical electric field strength (E/N)cr was defined. Its value for SF6 gas within the temperature range of 300 to 3000 K and pressure range of 1 to 32 atm was obtained by solving the Boltzmann equation with most recent atomic data, which allows the determination of the critical electric field strength Ecr at different temperature and pressure. The dielectric behavioral pattern of the breaker was then characterized by applying the Ecr data to the temperature and pressure fields obtained by a 2-D magneto-hydro- dynamics model encompassing all important mechanisms operating in the arcing process. The Ecr distribution at 80 and 110 \mus after current zero was then compared to the electric-field distribution to arrive at important information regarding the weakest point or regions in the design. Using a standard rate of rise of recovery voltage profile, the critical dielectric withstand level of the breaker was also predicted. [ABSTRACT FROM PUBLISHER]

Analysis of the parameters of valves is crucial to the optimization design of high-voltage self-blast circuit breaker. A magneto-hydro-dynamics model is developed to study the arcing process by considering the nozzle ablation. The influence of valves on the arc behavior is presented. [ABSTRACT FROM PUBLISHER]

A steady 2-D magnetohydrodynamic model of a capillary discharge is presented. Special attention is paid to the ablation/deposition process at the capillary wall, and the results show distinct 2-D features. [ABSTRACT FROM AUTHOR]