The invention relates to an earthing switch (1) for traction power supply systems (2), comprising a first main contact (3) and a movable second main contact (4), wherein the movable second main contact (4) can move away from the first main contact (3) to create a clearance, characterised in that the main contacts (3, 4) have a pre-ignition arrangement (5, 6) which is suitable for ensuring the short-circuit making capacity of the earthing switch (1). The invention also relates to a method for earthing a part of a traction power supply system using an earthing switch according to the invention.
