Switch for short-circuiting a direct-current power source

A switch including: first and second electrically conductive electrodes; an electrically conductive element; an electrically insulating medium separating the first and second electrodes and separating the electrically conductive element from the second electrode; and a pyrotechnic element including an explosive, explosion of the explosive causing the electrically conductive element to be driven into contact with the second electrode and the conductive element to be welded to the second electrode to form an electrically conductive link between the first and second electrodes.