Numerical Analysis of Arc Flash Phenomena in the Air Insulated Cable Box for an Electric Power Machinery

A cable box is a metal enclosure that provides connections to the main electric power machineries such as switchgear or transformer. Cable terminals housed in cable boxes have a high fire risk because very few cable boxes can withstand the pressure generated by a low impedance arc. And the cable boxes usually suffer from significant damage causing breakage of bushings between the cable box and the electric equipment. In case of transformer, oil is then spilled from the damaged bushing and the released oil generates the fire ignition. In this study numerical prediction for the pressure rise and propagation during the arc inside the cable box has been performed considering the effects of the shock waves, the deformation of the tank and the fluid-structure interactions between the pressure wave and the cable box. Based on the Euler-Lagrange coupling method, flow field and structure analysis has been conducted to predict pressure rise value of the cable box and the stresses of the wall. Two arcing positions such as line to line and line to ground has been chosen in order to consider how the initial arc point affects the pressure wave propagation and the shapes of pressure wave pattern due to the interaction with near wall.