Research on arc root stagnation when small current is interrupted in self-excited circuit breaker

Abstract

Self-excited DC air circuit breaker(SE-DCCB) has been widely used in urban rail transit for its excellent stability. It can realize forward and reverse interrupting, but has difficulty in interrupting small current due to the phenomenon of arc root sticking at the entrance of the arc chamber in the splitting process which is known as arc root stagnation. A coupling model of self-excited magnetic field and magnetohydrodynamics (MHD) is established for the SE-DCCB with the traditional structure. The magnetic field, temperature and airflow distribution in the arc chamber are investigated with interrupting current 150 A. The simulation results show that the direction and magnitude of magnetic blowout force are the dominant factors of the arc root stagnation. The local high temperature of the arc chamber due to arc root stagnation increases the obstruction effect of airflow vortex on the arc root movement which increases the arc duration time of small current interrupting seriously. Based on the research, the structure of magnetic conductance plate of the actual product is improved which can improve the direction and magnitude of the magnetic blowout force at the arc root, so as to restrain the development of airflow vortex effectively, and solve the problem of the arc root stagnation when small current is interrupted. The simulation results show that the circuit breaker with improved structure has a better performance for small current interrupting range from 100 A to 350 A.

Study of Arc Interruption Characteristics under Rated Current in Low Voltage Circuit Breakers

“…(1) The initial arc between the contacts in the air field and magnetic field under the action of continuous expansion, and an arc column with moving contact movement, expansion, and elongation. (2) The arc moves in the direction of the splitter, during which the arc is constantly bent and elongated, the arc voltage rises, and when it reaches the vicinity of the splitter, the arc column is squeezed by the splitter. (3) The arc enters the splitter area, the arc column elongates, and is cut.…”

“…The arc phenomenon involves the interaction of multiple physical fields, making it difficult to fully understand arc behavior through experiments. The arc burning process is a multi-coupled field involving an electromagnetic field, airflow field, temperature field, and radiation field [2][3][4]. In recent years, magnetohydrodynamic (MHD) modeling and simulation methods have been adopted to investigate the complex arcing characteristics in low voltage circuit breakers [5][6][7].…”

Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

“…The magneto-hydro-dynamic (MHD) model was used in Ref. [45], which is a kind of macroscopic model. The MHD model can describe the arc's morphology through temperature field distribution but ignores the arc's generation process.…”

“…To study the arc formation process further, in this work the medium-voltage DCCB (whose structure and working principle have been introduced in Ref. [45]) is taken as the research object and a fluid-chemical model considering the main reactions during the arc generation process is established. In contrast to the previous steady-state model, a transient solution is adopted in the fluid-chemical model used in this work and the electron emission boundary of the cathode is treated carefully, so that the model can simulate atmospheric pressure air arc discharge accurately.…”