Irregular bending of 500KV switchyard tubular bus 1

[jan63]

am working in a power station recently commissioned.It has a 500KV switchyard which is an extension of the existing one.Now attached pictures show quality of installation.We are pressing on the contractor that the irregular bending of the bus bar is not onle aesthetically bad but also the bending will cause the thickness of the tube to be less at the bends effecting its current carrying capacity.Can any one has more points to add to. Three pictures are attached.Two

of new one and one of old switchyard

 

[Palletjack]

You don’t have to explain anything to your contractor as long as you contract has “workmanlike manner” contained in it. Any other contractor will tell you that isn’t up to workmanlike quality.
“Fix it or we will deduct the price of another contractor repairing you shoddy installation”

 

[jan63]

Agreed but we have to reply or knock him out technically.His plea is "its working"

 

[Palletjack]

Your plea should again refer to the “workmanlike manner” clause in your contract. Period.
It would also work if it had a lower curve n it, or if it went three feet higher and came back down.
“It’s working” isn’t a valid argument for shoddy work.
I guarantee we would not accept that install in the first picture on our system.
Tell them to let the rookie that bent that pipe practice on someone else’s installation, no yours.
Contractors will push only as far as you let them.

 

[waross]

Unacceptable.

bending will cause the thickness of the tube to be less at the bends effecting its current carrying capacity.

This is not an issue with good bends.
Bends in IPS bus are not a problem.
Workmanship is.
There is no difference between bending aluminum IPS bus and bending rigid aluminum conduit.
Any one with experience bending bus and/or conduit would not accept that job.
It is unclear in the photos, but is the bus kinked at the bends? That is another no-no.
Any kinks will reduce the radius of part of the cross section and may cause added corona losses.
It was a very long time ago but I have had hands on experience with large IPS bus in a 500 kV capacitor station.
Our bends were subbed out to a machine shop and trucked to site. Memory fades but it was about 5" or 6" IPS.
(IPS: Iron Pipe Size. The same physical dimensions as Schedule 40 Iron Pipe.)

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

A further note:

bending will cause the thickness of the tube to be less at the bends effecting its current carrying capacity.

IPS bus tends to bend close to the center line. While one side of the bend stretches the other side compresses.
One side of the bend may be a little thinner but the other side will be a little thicker.
The offsetting differences may not be exactly equal, but the net difference is negligible.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cuky2000]

Bending bus is a common practice for HV substation application. The best time to address bending issues should be during the design process.
The ampacity of the bus will be minimum impacted by bending the tube since the current is highly concentrated in the surface of the aluminum bus due to the skin effect.

If properly designed, bending aluminum tube should be OK using proper material alloy and schedule.

Definitely the first picture with irregular bending of the bus looks weird and aesthetically questionable. The question should be asked if the interconnected equipment foundation and base are at the same level? In any case, the contractor should be directed by the engineer how to match interconnected equipment.

Below is a general guideline for bending rigid bus.

 

[LionelHutz]

The foreground bar in the first picture is a mess. The rest appear neat so you'd be hard pressed to argue they aren't acceptable.

 

[jraef]

As I said in the other forum where you posted this, my biggest concern would be if the physical strength of the bus has been compromised by bending it. Bending annealed material like tubing used as bus bars will lower its tensile strength. It may not be significant and could easily be factored into the design up front by an EE, but was it here? If not, then the contractor has taken it upon himself that the structural integrity and fault withstand capability is equal to or greater than the available conditions require. Can he prove that? I doubt it.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[livewire9]

The bus in the foreground of the first photo is comically bad. I've performed a number of bus calcs/modeling for up to 6" Al pipe. I can promise you for that short of a span the strength of the pipe (even with messing bending) is not a concern under ice, wind or short-circuit loading.

But, good workmanship is a legitimate claim to withholding a portion of their payment. There is also this. Look how the spaghetti bus is forcing the terminal of the switch (on the right, I believe it is a switch) downward. That could definitely cause operational problems with the switch mechanism and potentially lead to failure at the terminal after years of thermal stresses and environmental exposure.

 

[cuky2000]

I do concur with livewire9 that the short span is not a major concern from the bus bending under load. it is our experience that rather than the rigid bus, the post insulator and porcelain equipment such as the live tank breakers are the weakest elements in the bus system.

I wondering what drawings or documents the contractor did follow to perform the work and what kind of supervision was provided for 500 kV bulk substation during pre-commissioning. There are no excuses for the poor workmanship bad bus asymmetries and inconsistency to interconnect breakers one from the top and others from the bottom. Let us know if the contractor issues a Request for Information (RFI) and if any deviation from the design was approved.

As weird may sound, electrically and mechanically the substation may work OK but questionable regarding esthetics. Below is a couple of examples of substation designed with rigid bus bending and even asymmetric installation used in the power industry.

1) EXAMPLE #1:

2) EXAMPLE # 2:

 

[Power0020]

Just noted the messed dropper conductors in third picture with no spacers to tie sub-conductors together.

It appears to be more serious electrically and aesthetically than the bent bus, which (the latter) will "work", while the former will cause phase clearance encroachments, messy fields and SC forces.

 

[jan63]

Thank you all for the replies.With all this I will be in a better position to tackle the issue

 

[stevenal]

Cuky2000,

Those look like elbow bus fittings to me in example 2. You sure they are bends?

 

[cuky2000]

Stevenal: Looking closer to the picture #2, I agree with you that appear to be elbow fitting. Not sure if welded or compression type