Abstract
This paper is devoted to investigating the effects of high-speed elongation of arcs inside ultra-fast switches (ucontact≈ 5–80 m/s), through a 2-D time-dependent model, in Cartesian coordinates. Two air arcs in series, one between a stationary anode and a moving cathode and the other between a stationary cathode and a moving anode in the arc chamber, are considered. A variable speed experimental setup through a Thomson drive actuator is designed to support this study. A computational fluid dynamics (CFD) equations system is solved for fluid velocity, pressure, temperature, and electric potential, as well as the magnetic vector potential. Electron emission mechanisms on the contact surface and induced current density due to magnetic field changes are also considered to describe the arc root formation, arc bending, lengthening, and calculating the arc current density, as well as the contact temperatures, in a better way. Data processing techniques are utilized to derive instantaneous core shape and profiles of the arc to investigate thermo-electrical characteristics during the elongation progress. The results are compared with another experimentally verified magnetohydrodynamics model of a fixed-length, free-burning arc in the air. The simulation and experimental results confirm each other.
Highlights
Studies show that about 20% of industries have to change 5% to 10% of their circuit breakers (CBs) by 2020, due to the increase of the short circuit level [1]
Techno-commercial studies prove the feasibility of fault current limiters (FCL) and many investigations have been initiated and reported by EPRI and CIGRE [2] to design a practical FCL
The arc column boundary is defined as σ = 1, which is equal to 3300 K but the core is the gliding section of arc (σ > 600, which is similar to 6700 K in air temperature) which is passing more than 80%
Summary
Studies show that about 20% of industries have to change 5% to 10% of their circuit breakers (CBs) by 2020, due to the increase of the short circuit level [1]. Techno-commercial studies prove the feasibility of fault current limiters (FCL) and many investigations have been initiated and reported by EPRI and CIGRE [2] to design a practical FCL. Hybrid FCLs are among the most powerful current limiters developed so far and the most affordable idea in terms of cost [3]. In one of the hybrid FCL designs, a simple multi-contact fast switch (FS), along with the inherent features of the series arcs, has been used to commutate the current to current-limiting parallel branches [3]. Electromagnetic driven switches make 100-μs close/open times possible, which, in comparison with semiconductor power devices, are low-loss in ON-state and more reliable
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