Solution for Busduct Noise?

If the bars are correctly braced then look to the ducting it's self.
If it's of steel construction you could be getting resonance set up by electro-mechanical stress. You can soon tell by gently placing a finger on the ducting and feel for vibration.
Try cross bracing the ducting.

It could be due to eddy-current circulation. Try splitting the bus duct enclosure and introduce rubber bellows in between.

Dear sir

1)Please check the fish plate joints.

2)Fish plate joints should have been Electro tinned, other wise due to oxidation the fish plates will be poor conductor ,effectively local heating

3)If the contact pressure is not adequate then there there is bound to be contact resistance and local heating.

4)You can do Thermography study on the installation to identify the hot spots.

5)In the fish plates connections the bolt tightness may be in order but size of the bolt may be very much smaller for the holes on the fish plates.

6)If there 2 or 3 bus bars are used for each phase ,there should be packer pieces at regular interval to consolidate the phase bus bar.

7) You may try and introduce some more additional bus bar supports to arrest vibration of bus bars inside the duct.

8)Transformer vibration should not be transmitted to the Bus duct.It is better to have Rubber bellows at the transformer end.

For thermography study and more advise please contact privately

Over complicates the issue & then tries to sell you the answer

Dear Guest

Sorry to note your comments.I had to give the following explanations in view of your comments.

I was running industry in Chennai ,India manufacturing Bus duct and switchboards for the last 30 years.

Our bus ducts and Switch boards are installed in more than 500 installations in India.

In none of the installations we had come across such humming problems.

Since the person who posted the issue is also from chennai I had assumed that He would have procured the the Bus duct from one of the Fabricators in Chennai

Of late many fabricators in and around chennai are making Bus ducts and I had the opportunity to inspect these Bus ducts, as a Consultant.

Whatever the deficiencies I have noticed and possible causes have been listed in my reply , I have nothing to sell here.

In Bus duct manufacture and Installations , many small matters are to be taken care otherwise the installation becomes bad.

As a Guest you have made a passing remark on my suggestions.It would have better if you are registered as a member and given valuable suggestions to overcome the issue of Humming.

Please also note that I am a member of CR4 for the last 4 years and I have given suggestions for various issues and these were well taken by many members.

Dear sir

I would like to know wheather the problem of humming sorted out?

If so how the problem was sorted out?

This is purely acadamic interest.

Sir,

Not sorted out.

Is there any idea from your side.

please share with us.

T.u

Have you checked all the points indicated by ramvinod?

Perhaps it's humming because it doesn't know the words...