Lifting Transformers by Crane 1

[livewire9]

I am on a team designing a substation layout. We are trying to achieve a compact, economical arrangement. It has been proposed that a 3-transformer bay (or more) layout could be achieved with a drive path around the equipment; imagine an oval track around a small sub. I think it could be problematic for maintenance or replacement of the inside 138/12.5kV transformer(s) using a crane. Isn't it preferable to jack and slide xfmrs onto foundation pads? Is it a good design to risk having a transformer being lifted over other equipment (e.g. switchgear and bus) for the sake of saving a little bit of real estate?

 

[PHovnanian]

I'd suggest consulting with a crane company. Find out what sort of equipment they'll need to lift that sort of weight to a height sufficient to clear buswork and other stuff and then swing the load to a flatbed truck. And what the footprint of that will look like. You might find that the requisite 'oval track' will end up being quite large.

Jack and slide would seem to be easier, particularly in a working substation. Or some attention will have to be given to the layout of the buswork to allow lifting the transformer through with the requisite working clearances.

 

[thermionic1]

I think you are right. Maybe you can save space (not $) using GIS on the high side.

 

[davidbeach]

Maybe you can save space (not $) using GIS on the high side.

There is certainly some truth to that, but there are definitely some projects that just can't happen at any cost with an air insulated layout; sometimes GIS isn't more expensive, it's just the only option. Of our first six GIS installations, five were rebuilds of stations that had simply been tapped to the line into actual line terminal stations and the only way to fit what needed to be done into the limited space available was GIS. The sixth GIS installation was a new build, but on a very tight piece of property that couldn't have held 4 bays of air insulated BAAH, let alone any distribution.

A tool in the tool kit.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Parchie]

@livewire9 (Structural),
The transformer yard we have inherited has provisions for rail wheels on the transformer feet. Methinks the transformers slid to their final positions and then the rails were removed after installation/ transformer secured to their respective foundations. The other remote substation that we got upgraded used large cranes though. Try and weigh things and see which best suits you there.

 

[cranky108]

Few utilities rail transformers in a yard anymore. Moving a transformer on a flatbed, or one of the newer multi-wheeled flat transporters is a better option.
That said, we do use cranes for switchgear, and smaller transformers. But jack and roll is also used at times. And that is why many transformers have skids in the base.
Sometimes it does require outages to move transformers, as well as street closures, and more.
Actually, rails in a substation is a bad thing.

 

[TugboatEng]

Can you find a crane operator that is willing to work in a live substation?

 

[stevenal]

We lift over bus and switchgear when needed. Last unit was a 15/20/25 that came shipped oil filled and without radiators. It all depends on the crane and reach involved. Sometimes two lifts are required to reach the pad.

 

[cranky108]

One can also remove the oil to make it much lighter. And yes a transformer can arrive undressed, and be dressed by your crews.

 

[dik]

Just a caution, many GIS installs use CFCs for the 'insulation' part.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[davidbeach]

Haven't run into any GIS that uses CFCs, though there could be. In my experience the gas is always SF6, nasty stuff outside the enclosures in its own right, but with wonderful electrical properties.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[bacon4life]

Is it a good idea to have a half-acre of land sitting vacant just avoid using a crane once every 30 years? I wish I knew the right answer. For some layouts, having an oval track around the outside dramatically increases the amount of space the substation takes up. Although many of our distribution substation transformers are moved by crane, doing so requires a vast amount of room to allow both the crane and the delivery lowboy truck to park next to each other.

The preference can also depend which equipment you have easy access to. For me, procuring a crane takes a bunch of effort to hire, but gets the transformer moved in a couple hours (as long as the crane is available exactly when we need it). Jack & slide can be done using in-house crews and equipment, but it takes many hours to actually do the transformer move.

Tug- Although cranes do require very significant clearance distances, I regularly have cranes offload equipment in energized substations where adequate room is available. The new unfilled transformer is offloaded by crane to an unused corner of the substation. Once the transformer is dressed and filled, it is slid onto the actual transformer pad during a short outage window.

 

[cranky108]

A drivable area around the perimeter also allows a utility to meet clearances required by NESC, as well as access to equipment. It also allows a place to install underground distribution exits.
Looking at the substation outside my window, I also see the security cameras aimed to look down the drivable area to see more that one gate in each camera.
You should not install the security equipment in the same building as the controls, as it allows one easy target. So a large box in the yard for security is needed anyway.
Anyway a substation should have more than one gate, to allow more than one access way.

 

[prc]

In India, we normally provide bi-directional rollers (wheels) at the base of large power transformers. Rails are fixed on the foundation plinth(at standard rail gauge) and also ninety degrees to the foundation rail. Transformers are moved over rails by pulling on the lugs provided on the transformer base.
In three-phase transformer banks(of HV DC transformers, Generator Transformers) such a procedure is followed to replace any phase transformer, in the event of a failure. Of course, cranes are also used for this, if there are adequate clearances and availability of suitable cranes.

 

[cranky108]

The problem with rails is they would need to be grounded to the ground grid. In the US we use a substation rock to create an impedance for step and touch potential concerns.
Where two pieces of metal are exposed, and within a persons reach, the one that is not grounded (say a broken ground wire)will be at a different potential.
The substation rock becomes an impedance between a person and the ground grid below.
I may not have described it very well, but grounded if it can have a potential. Other wise, a high impedance.