He might be referring to the old crane span wires. They were all un- insulated and we used to tap off them, and drop down to disconnects where ever we wanted to feed whatever we were adding at the time.

 

Cable tray

 

Pipe and wire overhead or underground running to troughs was also common. Then disconnects would be attached to the trough with nipples.

 

Pipe. In fact, I have never worked in one plant that had cable tray. Bus duct yes.
I have seen it many times. But never installed it, ever.

 

I hate installing bus duct. We did a bunch of 800 amp and it was awkward and heavy and sqauare D’s Design is really dumb

 

Before bus duct and cable tray there is conduit and bus bars or troughs. Failed splices in troughs are as common as exploding bus cans in old plants. I've replaced a combination starter which had bakelite and phenolic and just 2 overloads in a cast steel box with a date of 1934 with a trough where the split bolt tape wore throigh and started a fire. I've also messed with a knife switch from an original power house (as in private generator...no utility) in a pipe plant near Philadelphia where the site was over 200 years old. No date found but I'm thinking around the 1930s or maybe a little earlier. It was around the corner from the Roebling wireworks which made the wire for the Brooklyn bridge and the smaller prototype in Cincinnati. That plant was almost pure rigid conduit everywhere except the tubular bus in the overhead substation.

Substations would run tubular bus bar hanging off insulators. The "crane rail" stuff other than actual crane rails is often basically just overhead pole wiring method adapted to places other than poles.

Cable tray was a European thing that started relatively recently in the 1960s then made it's way over here in the 1980s or so. Then we perfected it with exposed run cable so we could get rid of stubs.

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I've seen that only once. It was 400 amp, all insulated 4/0 on porcelain insulators. They would bug onto wherever they needed a circuit, usually 50 amps and sometimes 200 amps.
We were there to remove and replace it for 40 year inspection.
The guys loved scrapping all of that. We had removing and hauling it off it in our contract.
We had to do it over a weekend really fast as the employees of the place had been licking their chops waiting for us to finish, thinking we would just abandon it.

 

We have some old factories with something like the OP is describing, they are exposed round copper bars ran on insulators up in the steel, they have fittings that you can just tap a wire off of them and run the wire in conduit down to the equipment. the bars just run the length of the building, its just a long rectangle building. no fuses, no pics. they use round un-insulated busbars in substations still, although i don't remember ever seeing wire tapped off of them.

 

Around here alot of powerhouses and peakers are replacing non-seg bus with cable bus for medium voltage.

 

The inherent problem with bus duct is that you have a bus bar joint every 6-10 feet that is sealed up where you can't really inspect it. And then you have the same problem with the bus cans and the finger joints that rely on spring tension to hold the joint together. Over time all these joints slowly deteriorate as far as good connections are concerned. Once they get loose to the point where the connection heats up, the surrounding "duct" covers it up so nobody can visually or thermally inspect it until it goes into thermal runaway and then blows apart.


And nobody is willing to spend the money (labor) to remove all the covers and inspect the joints. And if you want to do IR inspection (best for this kind of thing), you need to hit at least 25% load and be running that load pretty much while doing IR inspection...for both practical and monetary reasons it simply isn't going to happen.



Combine this with the fact that generally most other wiring methods kind of resemble a "tree" instead of just one long "trunk" with a bunch of branches off the same system. But in the traditional wiring method if there's a section of the plant where you just run power from point A to point B you usually run cables and there are zero joints and almost no possibility of a loose connection where in that same span of bus duct you still have a joint every so many feet with no clear, open spans of uniform cable. And in plants that have bus duct part of the intent is that you can move bus cans and other parts around and reuse the same system and the same connections over and over again.


About the only solution I know out there is DTM (distributed temperature monitoring) which uses some goofy properties of fibers and some sort of laser scanning system to turn the entire fiber into a series of temperature monitors. Very, very awesome technology but someone has to run the fiber through the inside of the bus duct, preferably right next to every bus inside, AND pay around $500,000+ for the special laser scanner and high end processors and software that are needed for DTM. Again...simply not practical.


So bus ducts get failures, often quite spectacular, and there's little or nothing that can be done about it.

 

The machine shop I worked at had bus duct. I wouldn't say it scared the hell out of me, but it was in that neighborhood. The thing I've noticed with machine shops is, that whenever they can, they buy another machine tool, and eventually end up shoe-horning it into the last available piece of real estate available, starting with right under the bus duct and radiating out. Bus duct allowed this, and any form of reasonable access for an electrician was non existent. Add to this scenario the ever present. sticky film that comes from airborne coolant that coats everything in a working machine shop. Add the 20-40 years the duct has been in service, and the string of electricians and millwrights that have had their mitts on things. I habitually look and turn away when closing breakers and switches, but this bus duct was the only time I actually expected and braced for a blast (not that it would help). That said, its still, to the best of my knowledge still humming away, so it must be me.

 

Many years ago a company down the road called up and asked if we had a breaker and starter in stock that they could borrow. Its common when you live in the middle of no where to phone around the other company's and check there stock for parts.

I get there and was sent to there MCC which was one breaker connected to copper plates on insulators about 30' long. From there they made up jumper cables and connected them to breakers and starters that were mounted on frame work.

To my horror the electricians were between the bars and where the breakers are mounted sneaking through the jumper cables unbolting some jumpers with the power still on.

Thankfully a hurricane wiped out there mcc years ago and it had to be rebuilt to modern code.