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Switchgear Riddle No.9 - Medium Voltage Busbar Temperature Rise
How to calculate the suitable busbar according to temperature rise

Author : Ikhan - From: Pakistan
Tue, May 18th, 2010 - 12:34

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.
Author : Hamid - From: Iran- Firouzabad in Fars
Thu, February 10th, 2011 - 18:34
Some people say that surface area too should be considered because if the cooling surface area is high cooling takes place quickly and temperature rise becomes lower. For example consider a cross section of 200mm^2. If you choose 40x5mm,surface area will be 90 x length while for 50x4mm
it will be 108 x length. 
Author : Sinnadurai Sripadmanaban - From: Srilanka
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