Physical and theoretical aspects of a new vacuum arc control technology-self arc diffusion by electrode: SADE

101

Based on the improved two-dimensional axisymmetric magnetohydrodynamic model, the vacuum arc characteristics under different distributed axial magnetic fields (AMFs) were analysed in this paper. First, a uniform cathode spot distribution was assumed, and the influences of the azimuthal self-magnetic field and different radially distributed AMFs on the vacuum arc characteristics were analysed. Then, in order to simulate the real situation, according to the experimental results of other researchers, a non-uniform distribution of cathode spots was considered in the simulation. The simulation results showed that the effect of the current density of the cathode side on the vacuum arc characteristics (such as distribution of axial current density at the anode side and heat flux density to the anode) was significant.

Section: Introductionmentioning

confidence: 99%

Numerical simulation of vacuum arc under different axial magnetic fields

Wang¹,

Jia²,

Shi³

et al. 2005

101

“…At the same time, since the extinction of cathode spots will significantly affect the plasma distribution, their dynamic behavior is suggested to include cathode spot motion, splitting, and extinguishing phenomena. In order to obtain more realistic simulation results of the extinction process, the actual magnetic field configuration [30][31][32] is also considered in this work. In practice, an axial magnetic field (AMF) can keep the high-current vacuum arc in a diffuse mode, which is beneficial to arc interruption [33,34].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional hybrid simulation of vacuum arc extinction considering dynamic behavior of cathode spots

Li¹,

Cao²,

Cao³

et al. 2022

Vacuum arc extinction directly determines the plasma distribution at the current zero point, which affects the post-arc insulation recovery. In that regard, studying the extinction process to improve the post-arc insulation recovery ability is of great significance. In the extinction process, as the current decreases, cathode spots are extinguished and their distribution exhibits apparent discreteness and asymmetry, while the plasma density decays drastically. On the one hand, the discreteness of cathode spots makes the simulation setup regarding the whole cathode surface as a continuous emission source no longer applicable. On the other hand, the drastic decay of plasma density requires a simulation tool that can balance the computational efficiency and accuracy of the extinction process. To deal with these problems, the dynamic behavior of cathode spots is considered in this paper, and a three-dimensional hybrid plasma model is established. In order to simulate a more realistic situation, two applied axial magnetic field configurations for practical applications ─ bell-shaped and saddle-shaped configurations ─ are introduced. Both configurations are used to compare the position distribution and extinguishing sequence of cathode spots, as well as the evolution of plasma. More importantly, the method applied in this study can be employed to evaluate the effect of different magnetic field conditions on vacuum interruption, which would enable one to simulate the extinction process in a realistic manner.

“…An external magnetic field exerts a considerable influence on vacuum circuit breakers (VCBs). Many researchers studied the vacuum arc under the influence of magnetic fields [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. An external transverse magnetic field (ETMF) may weaken the interruption capacity of VCBs.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation on the influence of circuit breaker structure parameters on vacuum arc behaviors

Zhao¹,

Gou²,

Yang³

et al. 2020

In a switchgear, an external transverse magnetic field (ETMF) is generated by the U type loop consisting of the vacuum interrupter, external busbar and conductive rod connected to the vacuum interrupter. The ETMF will make the vacuum arc deflected and strengthen the contraction of the arc. This can increase the probability of breaking failure. To weaken the adverse effect of the ETMF, the real magnetic field data of the arc area with different structure parameters when the length of conductive rod, external busbar and phase distance is changed are obtained by establishing simulation model in this paper. Taking the real magnetic field data as the boundary condition, this paper obtains the typical parameters of the vacuum arc plasma with different structure parameters by using the established three-dimensional high-current vacuum arc magnetohydrodynamics model. The simulation results show that the ETMF makes the transverse magnetic field (TMF) of the arc area asymmetric, which leads to an arc deflection. Reducing the length of the conductive rod connected to the vacuum interrupter to 50 mm can effectively improve the asymmetry of the TMF caused by the EMTF, weaken the arc deflection phenomenon, make the distribution of the plasma parameters more uniform, and increases the utilization of the anode contact surface. Moreover, it can not only reduce the heat flux density into the anode as a whole, but also reduce the heat flux density in the high heat flux density area, so as to effectively reduce the degree of anode activity and improve the negative effects caused by the anode activity. The changes of other external structural parameters have less influence on the improvement of the vacuum arc deflection phenomenon. Increasing the phase spacing to 275 mm or reducing the length of the external bus bar to 100 mm can only slightly weaken the arc deflection.