Electrode assemblies for thermal plasma generating devices

A thermal plasma generating electrode assembly of the type having a central, water-cooled electrode and an outer sheath defining therewith a path for gas is provided. The sheath is made as a non-water cooled sheath of a high melting, electrically conductive material to avoid damage to the electrode as a result of stray arcing by attracting such stray arcing to the sheath rather than the electrode. In addition the electrode can be retractable within the sheath to enable the latter to be employed for making initial electrical contact with the co-operating electrode of opposite polarity for the purposes of ''striking'' or initiating the arc upon start-up