Busbar Design

" ... with operating voltage of 36V".

Don't think you've got any worries about flashover.

When i did testing at the lab i found out at 9kV and space separation of 20mm it started to Arc(flashover.) using this i spaced it 180mm. Will this be enough?

For voltage clearance distances, 36V DC is not going to "flash" over with bus bars 180mm apart (the breakdown voltage of air is about 1kV per mm, humidity dependent of course).

http://en.wikipedia.org/wiki/Dielectric_strength

For electromagnetic force stresses, with busbars 180mm apart and running parallel or crossing over each other at a point, the maximum force is going to be exerted on them (pushing them apart) with 55kA DC running thru the busbars. Given that you are probably running 150x22mm aluminium bus bar (or similar) this should help to mechanically prevent the busbars from moving, but you need to ensure that your bus bar supports are strong otherwise the bus bar movement could over stress joints and break insulators, causing the reactor bus system to mechanically fail at its weakest point.

Don't underestimate the electromagnetic force 55kA can exert between two parallel conductors, and don't assume that thick bus bars won't move.

Some examples as follows (there are better ones available on the internet) or consult your physics or electromagnetics text book (the formulas are in there to calculate the forces to allow you to design the supports accordingly).

http://en.wikipedia.org/wiki/Electromagnetic_force

http://www.tutorvista.com/content/physics/physics-iv/moving-charges-magnetism/ampere.php

http://www.google.co.nz/search?hl=en&source=hp&q=Force+between+Two+Parallel+Conductors+Carrying+Currents&meta=&aq=f&oq=

I am the electrical engineer at the plant

The bus bar layout described will probably be ok, but as an Electrical Engineer you need to perform the additional force calculations yourself to make sure it WILL be ok.

2-3 mm is more than enough space for the 36 volts you will be running. The bus bars should be bolted to each other because the magnetic field will try to force them apart. A plastic insulator can be used between them and thru-bolted using plastic bushings as insulators. If it makes any difference in your application, the closer the bus bars are to each other, the lower the reactive load they will present to your power supply. If inductance is not an issue, you can space them far enough apart that bolting is not required.

Thank you everybody for your assistance. so there will be no flash over.(arcing).but what about the electromagnetic stresses?. We have two conductors.Placed in a T position. the anode(positive bar) is placed perpendicular to the negatibe bar. With 55kA flowing there will be magnetic force pulling or repeling them. i refered to one formulae form Copper development association for rectangular cross section f=4.5*I*I *l/s* K * 10-8.is this formulae correct? what other formulae can i used to calculate the force that will be exerted due to electromagnetic forces with this T arrangement?.i need to know wether the support strength is good enough.sorry for my ignorance.

I'd be happy to help you out. Which way did you come in? Seriously though, all the bus configurations I work with involve parallel bus configurations that connect a source to a load. Therefore the bus bars are parallel to each other over their entire length. If you provide a sketch of your bus dimensions and layout, I may be able to provide more assistance. A bit of extra advice; since the normal current is 55kA, you might consider designing for the maximum fault or short circuit conditions. Your employer may not be happy if the bus fails under a fault condition.

thank you. yeah i realise that the fault current will definitly come into play. btw calculating fault level for busbars is the same procudure as calculating for cables since they both are conductors.i took it like that.correct me if im worng. the mechanical engineer is modelling it. unfortunatly i dont have a CAD on my comp. let me try explain.if it doesnt work out il try alternative. the busbars is for an silicon electroplating industry. it is a DC application. we have positive and negative conductor. the busbars are connected to rectifier.from there to main chopper and then to run chopper. yes the bars are parallel to each other. but the mech eng when modelling it came across a situation where the postive busbar is running perpendicular to the negative bar. like a T arrangement. so i adivsed him from my eletromagnetic theory that there will be a electromagnetic stresses since the current carrying conductors will exert a force due to magnetic field. he needs to know whether the 180mm space is sufficient between them. i dont know any formulae or table showing the sufficient spacing required?

Still finding it difficult to get a grip on the geometry, here. Maybe you don't have CAD, but how about Paint (or something better), Word (using Draw), or maybe a sheet of paper with a line drawing and a webcam/digital camera?

It's not that difficult to post a graphic.

here is a very rough diagram. another situation of which iv drawn.same project. operating current is 55kA and voltage is 36V. there is 12 parallel busbars with 380mm(wide) and 12mm(thickness) and length of 7.5m. i want to know the formulae to calculate the force that is exerted on the mild steel by the busbar which is separated by an insulator. the distance that is required-a.wat should (a) be?..and the distance -b.wat should (b) be?..the distance from busbars to supporting structure.?..since it is separated by insulator it is not a current loop.need help asap?..please..

Where is the return busbar?

Hold on a minute!

While 180mm is enough distance for 36VDC in air, you may need some creapage current break between the busbars at support points. This is especially needed when used in a wet environment where electrolyte could drip on flat surfaces between the busbars. Make sure that the space between is well drained with mountains and valleys to prevent liquid and dry chemical accumulation. DC current has a nasty habit of dragging traces of conductive metal between electrodes in corrosive atmosphere. Look at your car battery for sulphate creapage between the terminals over the years. Eventually, this can ignite an arc on the surface of the holders and propagate unsuitable material is used.

Also make sure that the bars are protected from accidental contact with conductors. Dropping a tool or one of the heavy electrode plate on them would produce a destructive short circuit and explosion that could kill somebody. What about a forklift accident? Could it contact the busbars?

Fair points, but anyone with a 2MW panel needs to take reasonable precautions, whatever the V & I.

Well done Roger!!

Keep investigating

( The Copalcor Team! )