Jia Shenli

Analysis of the Carbon Nano-Structures Formation in Liquid Arcing

Graphite electrodes were used for the direct current (DC) arc discharge in water. And high-resolution transmission electron microscopy (HRTEM) was used to investigate the products. Based on the experimental phenomena and nano-structure products, arc plasma characteristics in water were analyzed theoretically. Two growth regions and relevant growth modes were proposed to interpret the formation mechanisms of nano-structures by arc discharge in water. Furthermore, liquid nitrogen and cross magnetic field was applied to change the arcing state respectively, and new carbon nano-structures were obtained. Their formation mechanisms were also analyzed correspondingly.

Influence of Shock Wave on Turbulence in SF6 Puffer Circuit Breaker

Influence of the shock wave on the turbulence in a supersonic nozzle was investigated for a SF6 puffer circuit breaker interruption process. Turbulence is enlarged through the shock wave. Baroclinic generation of vortex causes flow separation and broadening of the arc cross section. V-I characteristics are slightly modified due to the shock waves influence.

Simulation of the Influences of the Pressure Ratio and Cu Vapour on SF6 Arc Characteristics

The inlet and outlet pressure of the SF6 high voltage circuit-breaker nozzle are of importance in determining the thermal interruption capability of a breaker. Besides, electrode evaporation is inevitable during the arcing process, which may affect the SF6 arc behaviour significantly. In this study a numerical investigation on the arc characteristics of a supersonic nozzle is carried out, by considering the influence of the pressure ratio between the inlet and outlet, and the Cu vapour. It is demonstrated that a lower inlet pressure may result in a higher arc temperature, a lower arc voltage and a smaller mach number, and Cu vapour from electrode evaporation may cool the arc significantly.

Development and study on iron core style bipolar axial magnetic field vacuum interrupter

In this paper, a new style of bipolar axial magnetic field electrode structure used in vacuum interrupters is developed and studied, which results in symmetric alternating axial magnetic field distributing intensively and evenly between the electrodes. Thus, no slots on the electrode are needed and the structure strength of the whole electrode is increased. Replacement of solid block iron core by a stromatolithic iron core reduces the eddy current and the lag time of the axial magnetic field behind the arc current. The results of tests show that this electrode structure can reduce the arc voltage and increase the interrupting current capacity of vacuum interrupters.

Observation and investigation of vacuum arc under various distributed AMF

The vacuum are under various distributed axial magnetic field is observed by high speed CCD camera. Through the images, the influence of AMF distribution on vacuum arc behavior is investigated. The results show that a proper nonuniform distributed AMF can control the vacuum arc to distribute more uniformly on the contacts and it could be helpful for finding a more effective AMF distribution.

Modeling and Simulation of Deflected Anode Erosion in Vacuum Arcs

In vacuum switch devices, the connection bus bar out of the vacuum interrupter will generate a transverse magnetic field in the arc column region, and under the influence of this magnetic field, the whole arc column will deflect from the electrode center, thus leading to deflected anode erosion. In this paper, a two-dimensional deflected anode erosion model is established, anode erosions under different deflection distance are simulated and analyzed, and results of anode surface temperature, anode melting and surface evaporation flux are obtained. The simulation results show that the deflected heat flux density will lead to deflected distribution of anode temperature, saturated vapor pressure and vapor flux correspondingly, and the morphology of the anode melting pool has also the same deflection. Moreover, the anode center temperature and its gradient along the y direction decrease with the increase of deflection distance. On the contrary, the temperature of the anode side surface, toward which the heat flux density deflects, increases with increasing deflection distance. Related experiments also verify the correctness of the model and simulation results.

The Plasma Channel Evolution Characteristics of Pulsed Flashlamps Working in an Array

This work is devoted to the study of plasma channel evolution characteristics in pulsed xenon flashlamps working in an array. Influencing factors on the plasma channel evolution process are studied, including pre-ionization pulse and neighbor flashlamps. It has been found that neighbor flashlamps affect the plasma channel by shaping the electric potential distribution, rather than by Lorentz force. Branching is observed in the plasma channels of the flashlamps in the middle of the array. Inconsistency also exists in the plasma channels of these flashlamps in different tests. The branching and inconsistency are both caused by the unique electric field distribution in these flashlamps. Besides, the pre-ionization pulse can help the main pulse plasma channel to develop more smoothly and faster, which will weaken the shock wave and benefit the mechanical strength of the flashlamp.

Numerical simulation of high-current vacuum arc with consideration of anode vapor

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.

Simulation Research of Magnetic Constriction Effect and Controlling by Axial Magnetic Field of Vacuum Arc

Based on magnetohydrodynamic (MHD) model of vacuum arc, the computer simulation of vacuum arc was carried out in this paper. In the MHD model, mass conservation equation, momentum conservation equations, energy conservation equations, generalized ohms law and Maxwell equation were considered. MHD equations were calculated by numerical method, and the distribution of vacuum arc plasma parameters and current density were obtained. Simulation results showed that the magnetic constriction effect of vacuum arc is primarily caused by the Hall effect. In addition, the inhibition of axial magnetic field (AMF) on constriction of vacuum arc was calculated and analyzed.

A kind of magnetic shield for vacuum interrupters

The effect of the external magnetic field mainly generated by external connecting buses on the vacuum arc is studied in this paper. This magnetic field which crosses to the vacuum arc will make the arc move out of the electrodes gap, and reduce the interrupting ability of vacuum interrupters. A kind of magnetic shield which can prevent the vacuum arc from being affected by the external magnetic field is developed in this paper. The experimental results show this magnetic shield could improve the interrupting performance of vacuum interrupters effectively.