Aluminum Busbar Support Distances - LV Switchboards

for copper busbars - read COPPER FOR BUSBARS - download from ICA website . . .

The distance between bus bar supports is calculated on the basis of the total stress acting on the bus bar conductors during a short circuit. If the bus bar has more 0.2% Proof Strength, like that of Coppoer bus bar, the insulator support span can be more. Whereas in case of Aluminium, the support span shall be reduced, as the 0.2 % proof strength of Aluminium is much lesser.

Firts of all you have to calculate the total stress acting on the bus bar conductors (both main conductor stress & the sub-conductor stress), then check if this is less than the 0.2% proof strength of the bus bar material chosen. If not, either change the bus bar material grade or reduce the stress by many menas, one of which is reducing the support span.

Did you check the IEC standard for LV switchboards, form 1,2 etc?. If not mentioned there send the SC level,size of busbar etc to manufacturer of busbar and ask for their recommendations.

You might have studied these already, if not ....

Schneider Electric's ECT 162,145,186 and 156 may give you some help. PDFs available from Schneider website.

Sir,

Deciding support distance/phase to phase center to center distance depends on the Short circuit current that the switch board has to cater.Based on this the calculation is to be made.It shall be same for aluminium or copper bus.

Are you sure? Aluminium being somewhat weaker than copper, so would need more supports (that is, space between supports should be smaller than for copper)?

Can you quote from the relevant IEC standard?.

IEC 61439 and all its parts are under revision. i have no access to them.

However, support spacing depends on design and will vary from one manufacturer to another. So, i doubt if IEC can lay down any detailed specs. The proof of the pudding is in the eating it is said, so the I_cw test is the final proof.

For the same current rating, aluminium and copper busbar sizes cannot be the same. As the mechanical strength of copper and aluminium are also different, support distances and phase to phase/Earth clearance also should be different. To support your view can you quote some standard or code?.