Interconnecting two tublar buses 3

[tareenmi]

I have a situation where a 69KV transmission substation with 3 inch tubular aluminum bus is welded to 69KV Generating Station (rated at 75 MW) bus with 2 inch tubular bus as shown in the attached picture. Does this provide a good connection? If not then what is best solution to connect two stations with different pipe sizes. Please note the two stations are new. Any suggestion will be highly appreciated.

M. I. Tareen, P. Eng.
Electrical Power Commissioning System Engineer

 

[Marmite]

The obvious place to make the transition from one size to the other is on the adjacent busbar support structure which is clearly visible in the picture. Two clamps, one 3 inch, one 2 inch bolted to the plate on top of the insulator. I've never seen the method used in the picture before, and I would question the competence of the installer. The weld looks pretty nasty, like a DIY job gone wrong. The pipes don't even look like a particularly snug fit, so most of the current will be forced through a very small area of weld. The longevity of the connection would also be questionable, once it gets subjected to Aeolian vibration. Looks like a ticking time bomb to me.

Regards
Marmite

 

[jghrist]

You could use a reducing splice connector. See

http://dmcpower.com/wp-content/dmc-downloads/products/pdf/PLK1010.pdf

for a DMC compression connector. Or use a factory weldment reducing connector such as Anderson WC

http://www.hubbellpowersystems.com/connectors/sub/standard/couplers/welded-aluminum/wc.asp

 

[stevenal]

You can check the existing integrity by checking it thermally under load. Might also put on your list for periodic checking. Replacement with a proper connector like jghrist recommended is probably the best solution. I like the DMC product, since it does not require the welding skill needed for weldment fittings.

 

[crshears]

Infra-red scanning under load as stevenal suggests would certainly reveal whether the joint is as bad as Marmite thinks...although I tend to agree with Marmite that the weld certainly has the look of a hack job...also that the cross-sectional area of the weldment appears very small indeed.

I don't know which company manufactures it, but I've seen what essentially looks like two clamps back to back bonded to each other with braided cross-link flex webbing. The clamps have cylindrical bores to match the OD of the tubular buswork, and provided all faces are well burnished beforehand and a non-ox compound is applied inside the joint, no welding is required for their installation.

CR

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