For enclosed switchgear it is seen that the oxidation of aluminium or copper starts at about 85-90°C. I t is for this reason that the operating temperature of a bus system is limited in this region.
At higher ratings it is therefore recommended either to weld the edges of the joints (straight-through or flexibles) to seal the openings and prevent any oxidation during operation, or to silver plate the joints. Silver oxide is a good conductor of heat and electricity. With the use of silver joints or welded joints, a higher operating temperature of the busbar and the joints is permissible up to 105°C as against 70°C as in (IEEE-C-37-20) or 85-90°C as in (IEC- 60439-2) in ordinary joints. With the use of silver plated joints therefore, the rating of a bus system may be improved and the use of metal optimized.