Consumer Electronics Query About Power-Poles

[emuboy]

Power-poles are everywhere, and so common we often fail to notice them.

On the standard, mid-voltage range powerlines with three wires (unsure of proper term) there are different powerpole heads where the wires are affixed, and I was wondering the purpose of each.

The standard poles simply have three insulators that obviously hold the lines in place from one pole to the next; but others are quite ornate with many wires and insulators and others with switches combined with insulators.

Any electricians on the board please help.

 

[Kram]

I'm not exactly sure what you are talking about, can you post a picture?

 

[Wallaby]

Do you want your possums fried, toasted or grilled? Otherwise, can't help.

I imagine there are all sorts of boosters and capacitors depending on how far you are from a sub-station and how much current is required on that part of the grid.

 

[DarkPhoenix]

crazy was wondering something quite similar the other day.

The big ornate things are likely to be boosters. Electrical current can only travel so far before its diminished similar to how you need boosters to increase your wifi signal if you get too far from your router.

 

[HarryTiger]

But where would a booster get its electricity from?

It's easy to see how signal transmission works, they receive the signal and send it out again stronger using an electrical source.

But the electricity is the original quantity in this case.

 

[Kram]

It's been a while since I've thought about this sort of s**t..

From memory I think the 3 lines/phases at the top are 11kV.. Then they then go through the big step down transformer box you see on some poles to 230V on the set of 4 wires below (3 phases and the new 4th wire which is a neutral out of the star point the transformer) which is what us consumers use.

The higher the voltage the less loss you get from 'volt drop' that's why they transmit electricity at high voltages over the long distances then step it down locally.

I think that's right...

 

[Simple Jack]

It's been a while since I've thought about this sort of s**t..

From memory I think the 3 lines/phases at the top are 11kV.. Then they then go through the big step down transformer box you see on some poles to 230V on the set of 4 wires below (3 phases and the new 4th wire which is a neutral out of the star point the transformer) which is what us consumers use.

The higher the voltage the less loss you get from 'volt drop' that's why they transmit electricity at high voltages over the long distances then step it down locally.

I think that's right...

That's what I thought it was as well.

 

[telsor]

But where would a booster get its electricity from?

It's easy to see how signal transmission works, they receive the signal and send it out again stronger using an electrical source.

But the electricity is the original quantity in this case.

They're not boosted in quite that way...

The signal (wave) the electricity travels at attenuates.

As most household appliances get a little narky when their supply varies by too much, it needs to be cleaned up, so the "booster" actually reshapes it.

 

[MrRockett24]

I work for one of Australia's largest electricity distributors (as in we own the poles and wires from Power Stations to your house).

I was an electrician but now am an electrical network designer.

Some Electricians may be able to help somewhat...but going off what I knew then compared to now....they wont be able to help you with this stuff.

There are 100's of different structures we build on electricity poles for many many different reasons.

Some are to reduce the voltage from 22,000Volts to 230V/400V (Transfoemers)

Some are switches both sealed gas units and open air break switches, so we can supply electricity from 2 different locations. Eg: Canberra has electricity coming from Melbourne and Sydney, with 3 switches...1 in North Melbourne, 1 In Canberra and 1 in South Sydney. Now say Sydney has a problem and needs to turn power off for a while, we can close the switch in Canberra to keep electricity flowing through there and open the one in south sydney to stop the electricity at that point, then we continue to feed electricity from the Melbourne to that open switch in South Sydney. Basically they are a way of maintaining the most amount of people on supply in the event of a fault.

We do have "Boosters" but not called that...actually called "Regulators" but are just a transformer. They are generally used in very rural areas as the 22,000Volts can drop to say 20,500Volts...so we use the regulator the same way as a transformer except from dropping from 22,000Volts to 230V/400V...its setup a tad different to raise the 20,500Volts back up to 22,000Volts again. They dont use electricity to work, its not the same as a signal booster....its all got to do with how electricity is generated...I can explain if you want but il leave it until someone asks as it may be a bit lengthy.

There are overhead High voltage bare powerlines that then go underground via an insulated cable.

Low voltage bare powerlines that do the same.

Automatic Circuit Reclosers (ACR's) that say a possum climbs up on the powerline and gets electrocuted...10 years ago the power would go off until an operator inspected the line to make sure it was safe to put back on...could take 6 hours and people were without power for that time.

ACR's work by turning off the power when it notices a fault on the line (Possum) and leaves it off for 3 seconds...enough time for said possum to have fallen/jumped off. Then it Turns power back on again...if it notices another fault...off it goes again...3 seconds again...then back on...if a 3rd time, it goes off and stays off until someone checks it and says its all good. Another way of keeping/getting people's electricity back on again as soon as possible.


Theres Heaps...but Please ask away....il answer anything you have and try and keep it simple cos some of the lingo we use can get a bit much.

Cheers.

 

[Wallaby]

I never cease to be amazed at the things I take for granted (like electricity) and how little I really know about it.

MrRockett's post just confirms how complicated our modern society is. It's rather humbling to consider how many experts there are out there all keeping a small part of it operating.

I remember once talking to a bloke who worked on repairing pot holes in roads. i said 'It's just filling in a hole, isn't it?'. Well, after about half-an-hour of technical discussion regarding things like vibration, laminar flow rates, drainage and such, I had a headache.

 

[MrRockett24]

I never cease to be amazed at the things I take for granted (like electricity) and how little I really know about it.

MrRockett's post just confirms how complicated our modern society is. It's rather humbling to consider how many experts there are out there all keeping a small part of it operating.

It is pretty funny because since I started this work...i notice the poles everywhere and take note of some oddities I may see...Thailand Honeymoon for example...some of our pics are of the structures they have there...pathetic I know.

Power poles...despite being EVERYWHERE...are one of the least vandalised items in society. Bet ya didint know that...they are soooooo dam obvious that no-one ever sees them.

A bit more tech sutff for ya...Theres a hell o a lot of these ACR's & Switches that are Remotely operated...so the opening and closing of the switches can be done without the need for someone to drive out and operate manually....pretty handy if its going to take 2hrs to drive there and its 2am in the middle of winter. Especially if its just a piece of bark on the line thats dropped off 10,000 NOW freezing customers.

There are 100's of switches all over the place because..like in my Melb/Canberra/Syd example...3 switches is pretty good...but it doesnt allow for much flexibility...say you want to shut off 50km of customers...smack bang between South Sydney and canberra...well with 3 switches..you cant....you have to drop off 100's of km of line and potentially 1000's of customers. AND when you take into account all the East/West locations that need power...it multiplies quickly and we need to maintain electricity to all them places and minimise disruptions.

So we install more and more switches to be able to re-direct electricity from all other places and basically localise a fault, or localise a shutdown (turn off power) for maintenance at...say... a 600m square area and only 50 customers maybe. Yes we can hit that type of accuracy.

Considering we used to drop off 100's of square km's and about 200-400 Transformers equalling 5000+ customers in semi rural areas EASILY - for say 6 hrs...thats a lot of people, so...if we can re-direct the electricity so <100 Customers are effected...and for maybe 30mins at worst (unless someone wipes out a pole, then it may be 2hrs) then everyone is happier.

There are also computer based schemes being developed as there are these 100's of switches all over the place...the computer scheme recognises a fault and will switch all the switches for that area and somewhat beyond into the best configuration to localise the fault and maintain these 100's/1000's of customers on supply...and its all done in less than 0.5 seconds.

Its a thing of beauty really...trying to keep >800,000 customers going so they can switch a light on at any time...and BAM...its on, or so their alarm clock doesnt reset

Part of the reason i stopped being a sparky really...

Electricity is fascinating stuff.

I Apologize for the long rant.

 

[Wallaby]

<Insert 'Get a Girlfriend' joke>

No, seriously very interesting. 'Electricity? Plug it into the wall. Switch On'. That's probably all 99% of the population (inc me) know. It's always good to increase one's knowledge (see my contribution to the 'Nerdy things you do' thread.

And I can bore with the best about IT Capacity Planning models (imagine mixing accountants with propellor heads).

 

[rocker_oz33]

l took out a power pole it had something on like a transfromer or something special.because over 6000 houses,movie cinema and shops lost there power.l knew something was wrong besides hitting a power pole everything just went black.with in 5-10 mins powercore people were standing around looking at it.everyone l know that l told about the cash hated me because there beer went warm,they were playing ps/computer games and did not save,were at the movies etc.

 

[rdhopkins2]

Very interesting indeed.
Some people might think of sparkies as a bunch of morons but there's actually a heap more to know than many realise. Photovolatics also, anyone?

 

[Caesar]

Very cool thread. I just learned a whole lot of new stuff.

 

[Carl Hooper]

Haha.. I'm an electrician. Power poles are actually rare where I live.

A lot of power is now underground, and go to a dome normally situated between two properties (metro area). Much more safer and easier to work with for us sparkies!

I'm amazed too sometimes, at how little I knew about electricity before becoming a sparky!

 

[joshuag]

Hi. I've always been interested in this type of thing also. It's a bit of a weird interest but since being a kid I've always looked at the poles when going on drives. I still do. I've almost had a few crashes in the past so I have to keep my eyes on the road instead.

One thing I've always wanted to know is what those tiny (or slightly larger) boxes are on the lowest crossarms, usually on the brace, where house wires meet up. The newer poles don't use these as much, and I know outside of Victoria you would see these in South Australia, then rarely in other states.

Also, sometimes I see higher voltage powerlines go underground between two poles in a suburban street. Are they underground transformers? I'm not talking about where new apartments are being built where the wires are moved underground for safety (or higher costing apartments maybe). I see poles from the 1960's with this. Sometimes I see this where those old brick substations are but other times there are no visible substations.

There are many things I'd like to know but I won't go crazy.

It's funny, I was walking to the shop before and took a back street and saw three small poles set up in someones backyard with all the devices and wires. You could probably almost use it as a clothes line. That's what spurred me to look online for discussions on this type of thing.

Thanks

 

[MrRockett24]

One thing I've always wanted to know is what those tiny (or slightly larger) boxes are on the lowest crossarms, usually on the brace, where house wires meet up. The newer poles don't use these as much, and I know outside of Victoria you would see these in South Australia, then rarely in other states.

Also, sometimes I see higher voltage powerlines go underground between two poles in a suburban street. Are they underground transformers? I'm not talking about where new apartments are being built where the wires are moved underground for safety (or higher costing apartments maybe). I see poles from the 1960's with this. Sometimes I see this where those old brick substations are but other times there are no visible substations.

There are many things I'd like to know but I won't go crazy.

Thanks

Go crazy mate, im happy to answer

Firstly, the smaller boxes on the lowest crossarm (low voltage) are whats called the "Service Fuses". These fuse the overheadwire coming in from the pole to the house. Some older places have the service fuse on the facia of the house...like mine, but newer ones are on the pole.

Secondly...some HV does go from pole to pole underground...so does LV by the way, generally its for crossing rail lines, major inptersections, bridges...but recently the trend has been out the front of residential developments as it looks nicer

 

[joshuag]

Thanks for the reply. One thing I also notice is a lot of the new poles are leaning when installed. When going to other states I don't notice this. I thought this might be because power companies have so many jobs to do with so many developments that they don't have time to let the poles set in the soil before hooking the lines up....so they shift. Just my theory. Could it also be the wood used? I know with the hexagonal shaped poles more popular in the 80's and 90's, a lot of them seem to bow with the pressure, compared to the new green poles.

Perhaps I've gone a bit off topic here haha.

Josh

 

[Simple Jack]

We do have "Boosters" but not called that...actually called "Regulators" but are just a transformer. They are generally used in very rural areas as the 22,000Volts can drop to say 20,500Volts...so we use the regulator the same way as a transformer except from dropping from 22,000Volts to 230V/400V...its setup a tad different to raise the 20,500Volts back up to 22,000Volts again. They dont use electricity to work, its not the same as a signal booster....its all got to do with how electricity is generated...I can explain if you want but il leave it until someone asks as it may be a bit lengthy.

Sounds like it would just be a transformer, or is it something more complex?

 

[MrRockett24]

Sounds like it would just be a transformer, or is it something more complex?

As I stated in the quote you put in your reply..."We do have "Boosters" but not called that...actually called "Regulators" but are just a transformer"

The way a transformer works is based around how electricity is generated. By the interaction of a pulsing magnetic field, and copper (coils) electricity is produced. The way a Transformer works is that the 22,000 Volts in goes throuugh (for the sake of the thread) a copper winding containing 22,000 turns. This copper is wound around an iron core in the shape of a doughnut. The interaction of the electriicty and the copper produces a magentic field which cuts the iron core and produces magnetic flux which flows through and around the iron core (Think the magnetic flux is like water the the iron core is like a water pipe).

Now the magnetic flux flows around and on the opposite side of the incoming Copper Windings, there is another set of Copper windings. These are far far less in number than the incoming. To gain a direct ratio of 22,000V In to 415V Out means that there are only 415 windings on the output side. This provides only 415V out as the magnetic flux cant "Cut" as much copper as there is only 415 windings compared to the 22,000 on the incoming side. Thus, the resultant voltage is less and thats how we get 415V.

The big question is howcome I ahve to use such larger wires for Low VOltage than I do for High Voltage. The reason is that there is a limit to how much POWER can be distributed to a certain area before it needs upgrading.

Example...the 22,000Volts on the high voltage may only have 100 Amps flowing. This provides a Apparent Power of 2,200,000 VoltAmps (2.2MVA) Now when this goes through the transformer, the output MUST equal the input...so with an output of 415Volts, the increase in amps is in the magnitude of Ratio of 22,000 : 415 for the voltage....the Amps are approx 5300 AMPS. (415 x 5300 = 2.MVA)

So the High voltage cables donty have to be very big...only required to take 100 Amps, however the Low Voltage Cables need to be large enough to take 5300 Amps. The cable to take this could be approx 4 Cables at the thickness of a average hunam forearm.

A regualtor is the exact same thing as a transformer (it is one actually) just in reverse. Instead of 22,000V In and 415 Out...its setup more for 21,000Volts In : 22,000Volts out, so as to bump the voltage back up anjd maintain a quality supply within Victorian Code.

How electricity is generated is that the super heated and super pressurised steam hits turbine fins (much like an aeroplane) and this interaction of changes the energy from a form of Pressure to Mechanical (it makes the turbine spin) Now the turbine is connected to the ROTOR of the generator which is all magnets and it spins (3000rpm) it is encased in the STATOR. A Large cylinder filled with Copper windings so when the Magnetic field is produced, (AND SPINNING VERY IMPORTANT) the magnetic flux cuts the copper windings and this changes the Energy from Mechanical to Electrical and thus Electricity is produced. Approx 11,700 Volts are produced in Power stations from memory, and this is fed into Large Transformers that take the 11,700 Voltas in and produce from 110,000Volts and 220,000 Volts to even 500,000Volts. The benefit of higher volts is that it can be sent long distances before we start to drop down to say 495,000 Volts.

Phew...sorry for rambling, but if there is anything needing clarification, im happy to try and explain in an easy manner.

 

[MrRockett24]

Thanks for the reply. One thing I also notice is a lot of the new poles are leaning when installed. When going to other states I don't notice this. I thought this might be because power companies have so many jobs to do with so many developments that they don't have time to let the poles set in the soil before hooking the lines up....so they shift. Just my theory. Could it also be the wood used? I know with the hexagonal shaped poles more popular in the 80's and 90's, a lot of them seem to bow with the pressure, compared to the new green poles.

Some newer poles may lean due to different stresses placed on them. Wind/Conductor Tension/Wind on the conductor.

However I get a lot of these and they are due to increased Rainfall making the ground soggier then normal which allows the pole to find its own Centre of gravity more than dry ground.

Also a lot of councils will cut away the side of an emabnkment to aid in drainage in some areas, thus reducing the amount of dirt at the footing of the pole and allowing it to lean.

We do straighten these when severe but realistically sometimes a 7degree lean is allowable from our design guidelines and dependant on the area.

There is no difference betwen the older hexagonal poles and the new Green ones. This is just a form of treatment on the pole much like Treated pine.

Cheers

 

[Simple Jack]

As I stated in the quote you put in your reply..."We do have "Boosters" but not called that...actually called "Regulators" but are just a transformer"....................................................................
......................................................................................
Phew...sorry for rambling, but if there is anything needing clarification, im happy to try and explain in an easy manner.

I missed that first bit obviously.

And thanks for taking the time for the explanation but I actually already knew all of that.