Investigation of arc splitters in an SF6 insulated medium voltage switchgear

Abstract

Splitter plates are commonly used in SF6 insulated medium voltage switchgears to interrupt the electric arc of moderate currents like the rated current in load break switches or the transfer current in switch-fuse combinations. The shape of the ferromagnetic plates determines the motion of the arc between them, influencing the switching performance. Besides, the electric field strength distribution around the plates is critical, as the high operational and test voltages can result in significant electric stress at the sharp plate edges. The proper adjustment of the plates and their support must prevent breakdown of the insulating gas under test voltages and an early pre-arc through the plates during a closing operation. By means of 2D and 3D finite element calculations, the paper investigates the motion of the arc between the splitter plates, their dielectric performance in a load break switch, and compares the calculation results with tests.