The size of these transformers which used to be mounted on street poles seems to have shrunk dramatically, how has this been achieved?

bob(from black rock) said:

The size of these transformers which used to be mounted on street poles seems to have shrunk dramatically, how has this been achieved?

The Rev could probably answer this properly but my guess is better insulation & cutting into safety margins.

Tamb said:

bob(from black rock) said:

The size of these transformers which used to be mounted on street poles seems to have shrunk dramatically, how has this been achieved?

The Rev could probably answer this properly but my guess is better insulation & cutting into safety margins.

Thankyou Tamb, “Pageing The Rev, would you please contact the switchboard?”

I suspect that they are using smaller transformers, just using a lot more of them.

Better engineering and metallurgy creates better efficiency, resulting in smaller transformers for the same performance.

Cheaper modern manufacturing processes mean cheaper transformers, allowing many smaller transformers rather a couple of larger transformers to be to be a cost effective method of improving reliability and reducing line losses.

sibeen said:

I suspect that they are using smaller transformers, just using a lot more of them.

lol

poikilotherm said:

sibeen said:

I suspect that they are using smaller transformers, just using a lot more of them.

lol

OK, I’d best expand.

Used to be that they would throw a 500 kVA transformer on top of a pole. Nowdays they use a 100 or 200 kVA instead, and therefore have to use more of them.

sibeen said:

I suspect that they are using smaller transformers, just using a lot more of them.

So where are they located? don’t see them anywhere?

The short story is that the paperwork to install a small transformer is vastly smaller than a bigger transformer, so they install lots of smaller transformers. It’s easier for the person running the job to put a smaller transformer in faster.

wookiemeister said:

The short story is that the paperwork to install a small transformer is vastly smaller than a bigger transformer, so they install lots of smaller transformers. It’s easier for the person running the job to put a smaller transformer in faster.

Also they are cheaper and easier to install, and replace when they fail and have fewer homes without power while they are doing it.

bob(from black rock) said:

sibeen said:

I suspect that they are using smaller transformers, just using a lot more of them.

So where are they located? don’t see them anywhere?

They hide them from view so people cannot see them, then they play where’s wally

Tamb said:

bob(from black rock) said:

The size of these transformers which used to be mounted on street poles seems to have shrunk dramatically, how has this been achieved?

The Rev could probably answer this properly but my guess is better insulation & cutting into safety margins.

I know nothing of electrickery.

The Rev Dodgson said:

Tamb said:

bob(from black rock) said:

The size of these transformers which used to be mounted on street poles seems to have shrunk dramatically, how has this been achieved?

The Rev could probably answer this properly but my guess is better insulation & cutting into safety margins.

I know nothing of electrickery.

Thanks Rev. My respect for your knowledge is in no way diminished.

Probably better core materials or design, and better winding methods, and better or more consistant insulation between them (which often includes oil), more stricter load balancing of phases maybe. Better cooling or heat transfer too possibly.

The other thing too is you can string more and higher voltage line and have more transformers to get down to consumer voltages and have more transformers that can be smaller. Rather than having less but big ugly bastards.

transition said:

Probably better core materials or design, and better winding methods, and better or more consistant insulation between them (which often includes oil), more stricter load balancing of phases maybe. Better cooling or heat transfer too possibly.

The other thing too is you can string more and higher voltage line and have more transformers to get down to consumer voltages and have more transformers that can be smaller. Rather than having less but big ugly bastards.

Yes, that’s what I said. :p

>Yes, that’s what I said. :p

And consistant = consistent, don’t want to be responsible for a contagion of bad spellng.

Pearl Shoal Waterfall, China

quite beautiful that, riff.

transformer efficiency I doubt will have changed greatly, unless theres been some revolution in materials making them

transformers in the streets are normally made from steel, full of oil and have very often have off load tap selection

sure the iron core might have changed slightly to make them slightly more efficient but I’d but that they’d already have mastered the materials thing ages ago – theres no where to go in this regard.

the worse place for a big heavy steel tank full of oil is up a pole, its harder to get to get maintenance done on it, its more dangerous to do work on it – then you’ve got the threat of the thing falling off it one day if temites eat their way through the middle. it was a silly idea putting them on poles in the first place, it was silly to continue with the idea.

the oil lasts longer the smaller the temperature differential between the hottest parts of the oil and the coolest parts of the oil based on where it is in the tank.

bigger transformers have pumps that pump oil around through radiators, the ones in the street rely on convection

wookiemeister said:

transformer efficiency I doubt will have changed greatly, unless theres been some revolution in materials making them

transformers in the streets are normally made from steel, full of oil and have very often have off load tap selection

sure the iron core might have changed slightly to make them slightly more efficient but I’d but that they’d already have mastered the materials thing ages ago – theres no where to go in this regard.

the worse place for a big heavy steel tank full of oil is up a pole, its harder to get to get maintenance done on it, its more dangerous to do work on it – then you’ve got the threat of the thing falling off it one day if temites eat their way through the middle. it was a silly idea putting them on poles in the first place, it was silly to continue with the idea.

OMG

Falls off chair

He can make sense, who’dofthought.

sibeen said:

wookiemeister said:

transformer efficiency I doubt will have changed greatly, unless theres been some revolution in materials making them

transformers in the streets are normally made from steel, full of oil and have very often have off load tap selection

sure the iron core might have changed slightly to make them slightly more efficient but I’d but that they’d already have mastered the materials thing ages ago – theres no where to go in this regard.

the worse place for a big heavy steel tank full of oil is up a pole, its harder to get to get maintenance done on it, its more dangerous to do work on it – then you’ve got the threat of the thing falling off it one day if temites eat their way through the middle. it was a silly idea putting them on poles in the first place, it was silly to continue with the idea.

OMG

Falls off chair

He can make sense, who’dofthought.

you’ll be amazed how resistant people are to the thought that transformers shouldn’t be on poles

the only things that should be on poles are dancers

wookiemeister said:

sibeen said:

wookiemeister said:

transformer efficiency I doubt will have changed greatly, unless theres been some revolution in materials making them

transformers in the streets are normally made from steel, full of oil and have very often have off load tap selection

sure the iron core might have changed slightly to make them slightly more efficient but I’d but that they’d already have mastered the materials thing ages ago – theres no where to go in this regard.

the worse place for a big heavy steel tank full of oil is up a pole, its harder to get to get maintenance done on it, its more dangerous to do work on it – then you’ve got the threat of the thing falling off it one day if temites eat their way through the middle. it was a silly idea putting them on poles in the first place, it was silly to continue with the idea.

OMG

Falls off chair

He can make sense, who’dofthought.

you’ll be amazed how resistant people are to the thought that transformers shouldn’t be on poles

the only things that should be on poles are dancers

Mmmmmm. Pole dancers.

Y’know – I agree! ;)

wookiemeister said:

sibeen said:

wookiemeister said:

transformer efficiency I doubt will have changed greatly, unless theres been some revolution in materials making them

transformers in the streets are normally made from steel, full of oil and have very often have off load tap selection

sure the iron core might have changed slightly to make them slightly more efficient but I’d but that they’d already have mastered the materials thing ages ago – theres no where to go in this regard.

the worse place for a big heavy steel tank full of oil is up a pole, its harder to get to get maintenance done on it, its more dangerous to do work on it – then you’ve got the threat of the thing falling off it one day if temites eat their way through the middle. it was a silly idea putting them on poles in the first place, it was silly to continue with the idea.

OMG

Falls off chair

He can make sense, who’dofthought.

you’ll be amazed how resistant people are to the thought that transformers shouldn’t be on poles

the only things that should be on poles are dancers

Damm

I wasn’t agreeing with all of your post. :)

If the infrastructure is on a pole then the transformer should be on a pole. Bringing the 66/22/11 kV down from a pole to a transformer and then back up to the LV lines is not a great idea.

>Bringing the 66/22/11 kV down from a pole to a transformer and then back up to the LV lines is not a great idea.

I dunno, dumb or/and drunk people like stuff to climb and swing from late at night. Keeps up newspaper sales.

Don’t know how true all this below is.

http://en.wikipedia.org/wiki/Energy_efficient_transformer

“In a typical power distribution grid, electric transformer power loss typically contributes about 40-50% of the total transmission and distribution loss. Energy efficient transformers are therefore an important means to reduce transmission and distribution loss. With the improvement of electrical steel (silicon steel) properties, the losses of a transformer in 2010 can be half that of a similar transformer in the 1970s. With new magnetic materials, it is possible to achieve even higher efficiency. The amorphous metal transformer is a modern example.”

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Amorphous_metal_transformer

“An amorphous metal transformer (AMT) is a type of energy efficient transformer found on electric grids. The magnetic core of this transformer is made with an ferromagnetic amorphous metal (e.g. Metglas), containing elements such as iron and glass former such as of boron, silicon, or phosphorus. These materials have high magnetic susceptibility, with low coercivity and high electrical resistance. The high resistance leads to low losses by eddy currents when subjected to alternating magnetic fields, a property particularly useful in transformers. Typically, core loss can be 70–80% less than with traditional crystalline materials.”

transition said:

Don’t know how true all this below is.

http://en.wikipedia.org/wiki/Energy_efficient_transformer

“In a typical power distribution grid, electric transformer power loss typically contributes about 40-50% of the total transmission and distribution loss. Energy efficient transformers are therefore an important means to reduce transmission and distribution loss. With the improvement of electrical steel (silicon steel) properties, the losses of a transformer in 2010 can be half that of a similar transformer in the 1970s. With new magnetic materials, it is possible to achieve even higher efficiency. The amorphous metal transformer is a modern example.”

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Amorphous_metal_transformer

“An amorphous metal transformer (AMT) is a type of energy efficient transformer found on electric grids. The magnetic core of this transformer is made with an ferromagnetic amorphous metal (e.g. Metglas), containing elements such as iron and glass former such as of boron, silicon, or phosphorus. These materials have high magnetic susceptibility, with low coercivity and high electrical resistance. The high resistance leads to low losses by eddy currents when subjected to alternating magnetic fields, a property particularly useful in transformers. Typically, core loss can be 70–80% less than with traditional crystalline materials.”

Again, that’s what I said. :)

sibeen said:

wookiemeister said:

sibeen said:

OMG

Falls off chair

He can make sense, who’dofthought.

you’ll be amazed how resistant people are to the thought that transformers shouldn’t be on poles

the only things that should be on poles are dancers

Damm

I wasn’t agreeing with all of your post. :)

If the infrastructure is on a pole then the transformer should be on a pole. Bringing the 66/22/11 kV down from a pole to a transformer and then back up to the LV lines is not a great idea.

that’s why you have all power underground

>Again, that’s what I said. :)

Yeah I’m just reading your mind, pinching your thoughts, telepathy you know. Channeling the Wook.

transition said:

Don’t know how true all this below is.

http://en.wikipedia.org/wiki/Energy_efficient_transformer

“In a typical power distribution grid, electric transformer power loss typically contributes about 40-50% of the total transmission and distribution loss. Energy efficient transformers are therefore an important means to reduce transmission and distribution loss. With the improvement of electrical steel (silicon steel) properties, the losses of a transformer in 2010 can be half that of a similar transformer in the 1970s. With new magnetic materials, it is possible to achieve even higher efficiency. The amorphous metal transformer is a modern example.”

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Amorphous_metal_transformer

“An amorphous metal transformer (AMT) is a type of energy efficient transformer found on electric grids. The magnetic core of this transformer is made with an ferromagnetic amorphous metal (e.g. Metglas), containing elements such as iron and glass former such as of boron, silicon, or phosphorus. These materials have high magnetic susceptibility, with low coercivity and high electrical resistance. The high resistance leads to low losses by eddy currents when subjected to alternating magnetic fields, a property particularly useful in transformers. Typically, core loss can be 70–80% less than with traditional crystalline materials.”

>the losses of a transformer in 2010 can be half that of a similar transformer in the 1970s

To put that in some perspective, a 200 kVA pole mounted transformer will have an efficiency above 98%.

>>To put that in some perspective, a 200 kVA pole mounted transformer will have an efficiency above 98%.

Which I suppose for a million watts through a transformer is twenty-thousand watts of loss, or similar to four small arc welders burning rods off inside the transformer.

transition said:

>>To put that in some perspective, a 200 kVA pole mounted transformer will have an efficiency above 98%.

Which I suppose for a million watts through a transformer is twenty-thousand watts of loss, or similar to four small arc welders burning rods off inside the transformer.

a drop in the ocean, there will be losses on the cables and all connections

then you’ve got millions of devices left on standby

the only reason they ever used AC was because they didn’t have the technology to adjust voltages with DC with any efficiency

DC uses all the conductor unlike AC

>DC uses all the conductor unlike AC

And how much skin effect do you get at 60HZ, wook.

50 for ostwalians sorry

More substantial than I thought.

http://en.wikipedia.org/wiki/Skin_effect

“The skin effect is due to opposing eddy currents induced by the changing magnetic field resulting from the alternating current. At 60 Hz in copper, the skin depth is about 8.5 mm.”

transition said:

>DC uses all the conductor unlike AC

And how much skin effect do you get at 60HZ, wook.

Quite a bit, actually. It is why switchboards are manufactured with busbars that are wide but not thick.

transition said:

>DC uses all the conductor unlike AC

And how much skin effect do you get at 60HZ, wook.

multiply the effect by all of the cable in the entire network from powerstation to kitchen and let me know

Jesus I am in fact learning shit today

“High-voltage, high-current overhead power lines often use aluminum cable with a steel reinforcing core; the higher resistance of the steel core is of no consequence since it is located far below the skin depth where essentially no AC current flows”

sibeen said:

transition said:

>DC uses all the conductor unlike AC

And how much skin effect do you get at 60HZ, wook.

Quite a bit, actually. It is why switchboards are manufactured with busbars that are wide but not thick.

probably for heat dissipation as well I bet, as well as for buildability

>Quite a bit, actually. It is why switchboards are manufactured with busbars that are wide but not thick.

Yeah come to think about it I note that, more bar.

transition said:

Jesus I am in fact learning shit today

“High-voltage, high-current overhead power lines often use aluminum cable with a steel reinforcing core; the higher resistance of the steel core is of no consequence since it is located far below the skin depth where essentially no AC current flows”

you don’t need to call me jesus

wookiemeister said:

sibeen said:

transition said:

>DC uses all the conductor unlike AC

And how much skin effect do you get at 60HZ, wook.

Quite a bit, actually. It is why switchboards are manufactured with busbars that are wide but not thick.

probably for heat dissipation as well I bet, as well as for buildability

99% skin effect, wookie. A circular bar would be stronger, and a square bar would be easier to work with. The busbars are 10mm thick, and that’s for a very good reason. In big boards you may have six 100 × 10 mm bars per phase. All having to be separated and supported.

>you don’t need to call me jesus

What struck me was I’d often thought about the weight to conductivity trade off when high strength steel cores were used (aluminium cable example) to reduce span sag and breaking presumably, so there’s my answer.

Only really though much about skin effect to apply to higher frequencies, particularly radio, and switching power supplies too.

sibeen said:

wookiemeister said:

sibeen said:

Quite a bit, actually. It is why switchboards are manufactured with busbars that are wide but not thick.

probably for heat dissipation as well I bet, as well as for buildability

99% skin effect, wookie. A circular bar would be stronger, and a square bar would be easier to work with. The busbars are 10mm thick, and that’s for a very good reason. In big boards you may have six 100 × 10 mm bars per phase. All having to be separated and supported.

how hard would it be trying to drill through square bar?

circular bar might well be stronger ever tried drilling through this shape and then trying to bolt it together? then you’ve got the problem of less surface area touching the connecting bar.

see?

this is why you use wide flat bar, you can bend it easily

you can connect it easily

you can drill it easily

transition said:

>you don’t need to call me jesus

What struck me was I’d often thought about the weight to conductivity trade off when high strength steel cores were used (aluminium cable example) to reduce span sag and breaking presumably, so there’s my answer.

Only really though much about skin effect to apply to higher frequencies, particularly radio, and switching power supplies too.

yeah

you’ve got soldering irons that use it too

wide thin bar allows for heat transfer to the air more efficiently

its a buildability issue too the best shape to run the current through isn’t always the best shape to work with, especially when you’ve got corners that the bar might follow

buildability is the one thing the designer tends to overlook

they don’t consider someone has to put their hand in somewhere, or try to tighten up a nut in an impossible place. the people who work on this stuff aren’t allowed input on basic matters.

Shorter the bolts through a bus the less stretch with thermal cycles probably + the thinner bus has less expansion.

the other problem with putting together large switchboards is that no one will be using a bench drill to make the holes

the best you might have is a centre punch and a hand drill strong enough to make a decent hole through the flat bar

no one will try to finish the hole they’ll just leave the burr in place

normally you can finish the hole by using a larger drill bit or a de-burrer – though ideally you should have another hand drill set up for just this purpose

ideally you should have a proper saw to cut the bar, ideally a band saw

I would saw its better to make this stuff on site simply because most plans don’t go to plan – have one person marking up and another checking – use the most responsible people to make the cuts.

when it comes to bolting the thing together I think you need to have a torque wrench to stop over tightening

you should tighten down once and mark the head of the nut, then get a different person to check all of the nuts and place their criss across the original cross it makes sure no nut is left loose.

wookiemeister said:

the other problem with putting together large switchboards is that no one will be using a bench drill to make the holes

the best you might have is a centre punch and a hand drill strong enough to make a decent hole through the flat bar

no one will try to finish the hole they’ll just leave the burr in place

normally you can finish the hole by using a larger drill bit or a de-burrer – though ideally you should have another hand drill set up for just this purpose

ideally you should have a proper saw to cut the bar, ideally a band saw

I would saw its better to make this stuff on site simply because most plans don’t go to plan – have one person marking up and another checking – use the most responsible people to make the cuts.

when it comes to bolting the thing together I think you need to have a torque wrench to stop over tightening

you should tighten down once and mark the head of the nut, then get a different person to check all of the nuts and place their criss across the original cross it makes sure no nut is left loose.

no one.. means that you have left out the watchmakers and other instrument makers.. you know, the blokes who make your tools.

So todays educational highlights are

1. skin effect at low frequencies like 50HZ are substantial, and about 8.5mm is the important figure if recall.

2. My soldering iron has an iron core tip so it doesn’t bend at higher temperatures?

transition said:

Shorter the bolts through a bus the less stretch with thermal cycles probably + the thinner bus has less expansion.

you need to use split ring washers or possibly nylocks – I’m not sure what the view is with nylocks – you’d hope that the heat wouldn’t be that much

the bars would have to be held away from each other if they were the same phase and held back from each other if different phases

the designer would have to account for fault currents trying to wrench bars apart or together

cables that are single phase need to be anchored down because of this kind of thing

the switchboard design is an art all of its own. to meet approval a major type of switchboard would normally be tested at something like 2V at a 1000A and covered in thermocouples

1. skin effect at low frequencies like 50HZ are substantial, and about 8.5mm is the important figure if recall.

——

Hey onty, do you ever get sick of over thinking?

>Hey onty, do you ever get sick of over thinking?

Nah mate there’s only so much sex a person can have in a day, how about you?

something like switchboard would need to account for expansion and contraction

watch out for circulating currents

don’t use cleats that completely encircle a cable with metal on a single phase cable it sets up circulating currents that will melt their way into the cable

the thickness of the bar that sibeen quotes is also most likely to resist bending forces

you’ve got skin effect but what happens when bars want to keep pulling together? you need a bar thick enough to resist these forces in normal operation and fault conditions

wookiemeister said:

the thickness of the bar that sibeen quotes is also most likely to resist bending forces

you’ve got skin effect but what happens when bars want to keep pulling together? you need a bar thick enough to resist these forces in normal operation and fault conditions

Which made big electrical stuff, heavy duty.

roughbarked said:

wookiemeister said:

the thickness of the bar that sibeen quotes is also most likely to resist bending forces

you’ve got skin effect but what happens when bars want to keep pulling together? you need a bar thick enough to resist these forces in normal operation and fault conditions

Which made big electrical stuff, heavy duty.

one of the the biggest costs would be the labour to put it all together I bet if its being put together on site.

unless its all been premade in china somewhere and you’ve just got some removalists that specialise in installing the cabinets

one major problem I found is the construction crews rarely have decent drill bits that can make nice holes, none of them own a drill doctor or the like.

An interesting thing to come out of this thread is power transformer efficinecy improvements by way of tweaking core materials, but just how widely used are these new core materials. Some of the transformers in operation would date back decades, but then the new core materials may not be widely used still, for cost reasons or something.

transition said:

An interesting thing to come out of this thread is power transformer efficinecy improvements by way of tweaking core materials, but just how widely used are these new core materials. Some of the transformers in operation would date back decades, but then the new core materials may not be widely used still, for cost reasons or something.

because its not worth replacing them for a sliver of efficiency improvement.

in the future we might just be using DC rather than AC

transition said:

An interesting thing to come out of this thread is power transformer efficinecy improvements by way of tweaking core materials, but just how widely used are these new core materials. Some of the transformers in operation would date back decades, but then the new core materials may not be widely used still, for cost reasons or something.

availability of being made accessible.