The conditions under which stable separate and coalesced multiple parallel arcs can be operated from a common power supply have been investigated and analysed. Results indicate that any number of stable parallel arcs can be maintained provided each arc is individually stabilised. Multiple electrode configurations relevant to industrial plasma processes have been investigated including coalesced discharges with multiple, individually stabilised, anodes and cathodes and discharges with multiple cathodes and a common anode. The results have been applied to a number of plasma processes including a horizontal multiple discharge system, capable of producing large volumes of ionised gas with a high degree of uniformity, a plasma furnace incorporating multiple de plasma torches operating from a single power supply, and a high-current, non-consumable, multiple cathode assembly for use in do arc furnaces. A horizontal multiple arc system and a plasma furnace incorporating three plasma torches have been designed at the University and are in use for processing material at Cambridge University and in industry respectively.