BUS DUCT DESIGN

follow the standards IEC 61439-6 for Bust ducts

You can put silica gel bags inside the Bus duct.Then you can provide Louvers to the Bus duct.nothing will happened.

What is the degree of protection of the bus duct enclosure?

You have not indicated the busbar material.If this is Aluminium , sizing of bus bar is not adequate to carry 4000 A for an ambient temperature of 50 deg C.

Please check.

Bus bar material is aluminium and Ambient Temp is 40 Deg C.

The 4 nos 150 x 10 mm Aluminium Flats per phase and 2 nos 150 x 10 mm Aluminium flats for neutral will have open air rating of 4680 A for temperature rise of 50 deg C over an ambient of 35 deg C

Further ratings are to derated for Enclosure and temperature rise.

In your case the ambient temperature will be 40 Deg C, therefore temperature rise will be restricted to 45 deg C.The deration factor will be 0.94

Further the ratio area of conduting material to area of enclosure is more than 5%.therefore deration factor for an Indoor busduct located in a well ventilated room 0.65

Therefore total deration would be =0.65*0.94=0.611

The current carrying capacity of 4 nos 150 x 10 Al.flat inside an enclosure of 800 x 500 mm for temperature rise of 45 deg C,over an ambient temp of 40 deg C would be =0.611 x 4680=2859 Amps only

if you require any further details please contact privately.

Question (you seem to know what you are talking about!): What would be the ratio difference when changing from copper to aluminium? Our Cu busbars are continuously stolen, and my electrical staff are planning to change to Al due to lower theft value. They are used in open air (indoors!), ambient never over 40 deg C. I recall the size in the order of 80x10 or so. (We have already replaced the outdoor busbars with ACSR conductors, which stopped theft dead, but cannot use it indoors as easily due to bends between wall bushings and the rectifier connections.)

For replacing 80 x 10 copper flat into Aluminium flat you may have to go infor 160 x 10 mm Electrolytic grade Aluminium flat.(tentative calculation) This again we have to calculate , based on the current ,ambient temperature ,enclosure size and material of enclosure etc.