Numerical Study of Arc in SF6 Gas Circuit Breaker with Externally Applied Magnetic Field

The influence of an externally applied magnetic field on the characteristics and the transient behavior of the arc in a gas circuit breaker is examined by means of three-dimensional time-dependent numerical simulations. It is assumed that the gas circuit breaker has a ring-shaped permanent magnet and an arc is exposed to the externally applied magnetic field. Numerical results demonstrate that the rotation of arc induced by the Lorentz force produces a three-dimensional spiral structure of the arc. As a consequence of the rotation, the arc shrinks and the arc temperature decreases remarkably just before the time when the arc current is zero, so that applying the magnetic field increases the arc voltage. The numerical results also show that a swirling flow generated by the Lorentz force carries a thermal energy toward the thermal puffer room mainly by the convection during the high arc current phase, and as a result the pressure in the thermal puffer room increases. (C) 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.