Easy to insulate against 220V, maybe a little trickier when it's 8,000. They're putting in a new 115,000 V line near me, the project manager told me they work at line potential, as there's no insulation that can cope.
Up to around 500 volts many things will work for insulation. Over 1000 volts and things that will protect you from the lower voltages will just arc through and provide no protection at all.
I saw a program on TV about the very high voltage workers. They would use long insulated poles and wipe them down and the poles had a mark on them as to not put your hands past that mark.
Even more interisting was the ones on the transmissioin lines where they wold have a helicopter put the man on the wiring. The voltage was so high the man was in a special suit. Seems to me it was a conductive suit to pass the very high voltage around him as evenbeing very close to the lines was bad for him.
... at least not fiscally prudent anyway. Since they do bury high voltage lines some places it can obviously be done. The added bulk and weight is not necessary on overhead lines tho and most medium to high voltage conductors are not insulated. Without insulation, they can use smaller wire. (conductors in free air). This is the label off a spool of medium voltage cable that they used for a buried 13.2kv run underground and then across the bay here.
Yes, there is insulation that will stand the veryigh voltages. I worked with a large company that converted the main power to 13,200 volts and fed it around the plant to about 20 of what we called substations . This was usually ran in open wire trays. The wire is insulated,but just layed in the trays. Some inside and some outside. There it was converted to mostly 480 volt 3 phase and often 600 amps.
Most cars have around 10 to 20 thousand volts on the spark plugs and the wire is insulated.
One of my ham radio ampifiers has a seperate power supply that sends around 2600 volts DC down the wire. The wire is less than 18 guage, but the insulation is about 1/2 inch in diameter with the wire in the center. It is special insulation compaired to the other wires.
It is the common things around that are not very effective much above
1000 volts. So if any of the power wires that are not on the 240 volt side of the common pole transformer are laying around, do not try to move them unless you know what you are doing.On Thu, 16 Jul 2020 10:23:28 -0400, Ralph Mowery posted for all of us to digest...
Part of that may be for static electricity.
Sounds like an interesting place (but some industries are not-so-fun).
In the NEC thing changed to high voltage at 600 V. In the 2017 NEC in many places that was raised to 1000 V.
Another fairly common high voltage wire is for neon signs. The largest transformer I have seen is 15 kV, but has a grounded center tap. Wire is
5, 10, 15 kV.If a neon sign wire is in a grounded pool of mercury the voltage gradient from the conductor to the surface is uniform and the insulation is happy. If the wire goes through a thin sheet metal hole and lays on the sheet metal the voltage gradient is concentrated at the sharp edge. Even though the voltage is within the insulation rating, the gradient (volts per mill) may exceed the rating and deteriorate the insulation from the surface in, causing failure. (The wire should go through an insulated bushing.)
The U of MN had a small system in a spherical glass flask about 5" diameter. The inside of the glass had a transparent conductive coating with a phosphor coating on top of that. A tungsten wire was etched to an extremely sharp point maybe 4 atoms diameter. The point was placed at the center of the sphere, the system was evacuated to a good vacuum, and at least 6 kV was applied between the wire and conductive coating with the wire negative. The electric field was concentrated at the point, and because it was so sharp the field at the point was strong enough to strip electrons out of the tungsten atoms. The electrons accelerated to the conductive coating and lit up the phosphor with the pattern of the atoms.
MV (distribution voltage) cables can have the same problem with uneven fields. It is common to have a semiconductive coating at the outside the insulation with grounded wires on the outside the insulation (shielded MV cable). There then is a problem terminating the stuff. In the good old days a pothead was used (MV electricians had to work with potheads). Now there are kits to install that give uniform voltage stress reduction at the ends.
A few times I have driven past where wires from a large transmission tower converted to an underground run. It is impressive.
I worked as an electrician and instrument technician. Covers a very broad ammount of equipment. Worked on pnumanic (air controled) controllers, computer controlled came later to replace that. It was a plant that made polyester from raw materials. We mixed a white powder tht looked similar to flour called TA for short and Glycol (similar to the antifreeze in cars) and a few trace chemicals. Heated the mix to around 300 deg C and extruded it to several products. One looked like a bale of cotton, another was string and the third was pieces that were about 1/8 inch square and 1/2 inch long . That was shipped to places that made the plastic bottles like the 2 liter drink bottles. Most areas of the plant the workers did very little work most of the time, but just watched the equipment run. They probably worked 2 hours out of an 8 hour shift.
For a long time it was a great place to work with around 3000 people. Then the jobs went out of the country and when I retired there were around 400 people. About 2 or 3 years later it totally went out of business. It was built about 1965 closed about 2018. Had about 30 acers under roof.
The power came in to a building at an unknown voltage to me. Then converted to 13,200 volts and destribuited around to our 'substations' to be converted to 480 volts 3 phase. Then to other rooms that had the motor contactors and other items.
You can see a picture on Facebook under FII Buddies.
Sort of, they really just added the category "1000v or less" but there are still plenty of articles that deal with "600 or less". That is mostly driven by the materials we use.
Believe it or not, they have a 1,100 Kilovolt direct current span across the Yellow River in China. The pictures of that are unbelievable. That thing is up in the clouds, big time. I think it's called the Changji-Guquan or something.
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