Incorrectly sized lugs on busbars

I agree, not good practice and potentially likely to fail.  Have they used a large thick appropriate material washer under the bolt/nut.  If not I would say definatly needs redoing.  With a suitable washer or better still well designed clamp plate it might be OK.  That will depend on the contact surface areas and clamping force.  Washer material expansion may also cause problems depending on thickness and material compared to the bolts.

Hope this helps

It rather begs the question of if the busbar is undersized, or if not, then if it  should have been bored with a larger hole... Probably  a bit late to do it now !!

The important thing is that the full flat side contact area of the lug is held against an equally flat region of the bar, and an undersized nut or bolt head will tend to dish the lug at at microscopic level. I agree that load spreading with washers is the way to go to get full area contact, but it will always be a bit off the proper installation.

M.

Whilst 300 mm2 lugs may not be an off the shelf item in some wholesalers, I wouldn't have thought the Tx was either and that too needed to be ordered. I wonder why they were not ordered.


As to the "correctness" of the lug size compared to bus-bar hole size, I would have thought an enquiry to the Tx manufacturer for their advice would carry some weight.


You do not mention crimp tool compatibility with the make of lugs, crimp tool calibration, torque setting of the bolts used, use of PVC tape over the lug........................


Regards


BOD

I agree with the sentiment above, and would add that the correct size is readily available from reputable vendors. Indeed long-palm lugs are M12 and might be what the transformer manufacturer was allowing for.


I will admit to using spreading washers plus Belleville washer etc to terminate M12 lugs onto M10 final circuit equipment where there wasn’t a small enough bimetallic lug available, but this has only occurred with the express written approval of both the equipment and lug manufacturers and the cable was under-loaded (oversized due to volt drop), checking the washer dimensions to verify contact areas and a detailed method (torque etc as BOD says) provided to site. I still might not have been comfortable if the termination was expected to run at full load temperatures.

Thank you all for the feedback, i did think to myself when inspecting this why they just never used correctly sized lugs and bolts to match the busbar hole size. Its a new install so why wouldnt you. We have consulted the manufacturer before signing our commissioning sheets and letting this go online under load. After all this is a 11kv 3MW transformer. We don't want any unwanted heat transfer when under massive load.