What are these wires that are connecting powerlines?

[Nathi ORea]

TL;DR Summary

I am interesting in knowing what these 'wires' are that seem to be connecting these powerlines. I don't know much about electricity, but isn't 3 lines the various phases and one a neutral wire? Is this right?
Why would they join them like this?
There is construction a little further down (should be able to see in the photo). Maybe that has something to do with it.
I am in Australia, near Sydney, if that helps.

 

[berkeman]

My guess is that they are a safety short on de-energized powerlines while they are being worked on, but that's just a guess. @anorlunda would know for sure.

 

[anorlunda]

I agree with @berkeman , shorting cables protecting workers working on the line.However, that is a very strange line. I see 5 strings of insulators, indicating 5 conductors. 5?! Nobody uses 5 to my knowledge.There is also a second set of shorting wires visible. Three also appears to be a 6th site with no insulators, and something resembling a hammock on the pole.

Therefore, I can't rule out something bizarre and unconventional instead of shorting straps.

 

[berkeman]

However, that is a very strange line. I see 5 strings of insulators, indicating 5 conductors. 5?! Nobody uses 5 to my knowledge.

OP says he is from Australia, so maybe @davenn can comment.

and something resembling a hammock on the pole.

Wait,what?! Maybe for mandated rest periods?

 

[Nathi ORea]

Thank you so much for your reply!

The 5 does look a little out of the ordinary, if I get what you mean. There usually seems to be only 4. I put a picture of the wires just in front of my house.

Is the boxed thing the 'second set of shorting wires' you mean? They seem to be everywhere. I assumed they are non-conductive rods just to keep the wires apart in case of wind or whatever else?

Here are some in front of my house.
The lower one is the phone line.

 

[berkeman]

Is the boxed thing the 'second set of shorting wires' you mean? They seem to be everywhere. I assumed they are non-conductive rods just to keep the wires apart in case of wind or whatever else?

Of course those aren't temporary shorts. The rigid rods are indeed to add structural separation to the wires. That is completely different from the hanging shorting wire assemblies with the mechanical clamp jaws holding them onto the wires.

Was the power out to your neighborhood when you took this picture? If not, that would be very strange.

 

[Nathi ORea]

Of course those aren't temporary shorts. The rigid rods are indeed to add structural separation to the wires. That is completely different from the hanging shorting wire assemblies with the mechanical clamp jaws holding them onto the wires.

Was the power out to your neighborhood when you took this picture? If not, that would be very strange.

I am not sure if power was cut. I just drove past it and wondered these clamps were connecting the wires. This is a bit away from my house.

There is also a second set of shorting wires visible.

Sorry. I can't see a second set then.

Can I ask what those rods are made from? They look metallic to me.

Thanks again.

 

[Baluncore]

There is also a second set of shorting wires visible.

Of course those aren't temporary shorts. The right rods are indeed to add structural separation to the wires.

The straight connector is a white fiberglass rod that prevents wires swinging and contacting in strong winds. They do funny things here in Australia, the fiberglass rods are also used to support electric fences.

 

[Nathi ORea]

The straight connector is a white fiberglass rod that prevents wires swinging and contacting in strong winds. They do funny things here in Australia, the fiberglass rods are also used to support electric fences.

Ha ha.. What do you mean by funny? The rods aren't usually used overseas?

They don't ever seem to look 'white'?

Thanks so much for your reply

 

[Baluncore]

They don't ever seem to look 'white'?

That is probably because of atmospheric polution.
Down here everything is washed by the purest of rain.

However, that is a very strange line. I see 5 strings of insulators, indicating 5 conductors. 5?! Nobody uses 5 to my knowledge.

My guess is that the fifth wire is an Earth wire to handle the electrical storm currents. It is mounted on an insulator to prevent pole currents that would otherwise set fire to the dry wooden poles.

 

[anorlunda]

My guess is that the fifth wire is an Earth wire to handle the electrical storm currents. It is mounted on an insulator to prevent pole currents that would otherwise set fire to the dry wooden poles.

That's possible, but there is no reason a shield wire should have exactly the same length of insulation string as the power lines. Shield wires are grounded as soon as possible because we don't want the surge jumping the air gap to other conductors.

There's still a 6th mystery wire with no insulators. I circled it in red. It can't be phone or Internet, because those things are always lower on the pole than power lines.

And a mystery object I marked in blue. and a single wire circled in green leading down to somewhere.

 

[Baluncore]

The red and green circles mark bundles of four insulated wires going to the customers premises. A catenary wire would have an insulator and be anchored to an eye-bolt through the pole.
I think the blue circle marks the where the two bundles are being gathered. There may also be service fuses there, which would explain the bulk.

 

[Borek]

6th wire: I saw similar thick, twisted wires in PL. I was always under impression they are for telecom/internet connections, just reusing existing poles.

 

[Nathi ORea]

Ok. so I drove past those lines again, and I tried to take some better pictures.

Here are the two posts which the clamp wires were between. You can see the wire clamps, and the hammock pole off in the distance

A look up at the first post. Do all these wires seem to be going into the one that's below?

Then here are these clamps I was wondering about and the other post with the hammock.

Then here is a picture of the 'hammock' pole.

Does this make it any clearer as to why these wires would be connected like this. It is kinda killing me.
I have really enjoyed all your input so far!

Was the power out to your neighborhood when you took this picture? If not, that would be very strange.

There doesn't seem to be any work being done in the area, but maybe there was recently. Surely this area would not be without power for this long.

 

[Baluncore]

The fifth wire could be the street light power that turns the lights on at night.
The "hammock" is insulation, with black and yellow stripes. It suggests that a crane has been operating above the wires.
The insulation would be installed for a period of time during construction of the adjacent building.

The insulation is often long term and is probably quite independent of the Earth jumper leads, which would only be used for a short period, unless the power had been transferred to underground.

 

[anorlunda]

That's much better. It looks like two single-phase circuits, possibly with a shield wire on top. The wires going down and diagonally are to a customer's entrance (as @Baluncore said).

I still think the jumper wires are shorts. It could be that service to those two single-phase circuits is cut off for reasons we don't know.

It could be that the yellow insulation blanket was there because men were working up there. They could remove the blanket before removing the shorting straps to restore those circuits.

Just because those circuits are shorted, does not imply that any customers are out of service. Most distribution circuits make a U shaped round trip from/to the substation. You can cut out anyone section of the U and everyone still gets power, although the direction of power flow in parts of the wires may reverse.

Real life power distribution can be very messy. It's hard to make any general statement which is always true. Therefore any answers in this thread (especially mine ) may be incorrect.

 

[Nathi ORea]

The insulation is often long term and is probably quite independent of the Earth jumper leads, which would only be used for a short period, unless the power had been transferred to underground.

The insulation is the yellow and black tape is it? So what would the shorts actually do in that case? Safety for workers (like someone said before)? Would the neutral wire still connected to the grid while the others aren't?

That's much better. It looks like two single-phase circuits, possibly with a shield wire on top.

I would really appreciate that you point out what the two single-phase circuits are? I thought there was three.

Real life power distribution can be very messy. It's hard to make any general statement which is always true. Therefore any answers in this thread (especially mine ) may be incorrect.

I am sure it is messy. I have always wondered about how many parts of our grid works, and Googling doesn't often help in explaining. I think I probably don't get some essential basics.

I think if I keep asking specific questions on this forum as to certain aspects of our power infrastructure then I'll get there in the end

I really appreciate everyone's time

 

[berkeman]

I am sure it is messy. I have always wondered about how many parts of our grid works, and Googling doesn't often help in explaining. I think I probably don't get some essential basics.

I think if I keep asking specific questions on this forum as to certain aspects of our power infrastructure then I'll get there in the end

Have you read through the series of Insights articles by @anorlunda about the AC power grid?

https://www.physicsforums.com/insights/ac-power-analysis-part-2-network-analysis/

 

[anorlunda]

So what would the shorts actually do in that case? Safety for workers (like someone said before)?

Yes safety for workers.

I would really appreciate that you point out what the two single-phase circuits are? I thought there was three.

Red single phase circuit 1
Blue single phase circuit 2
Yellow, shield wire lightning protection.
Three Green, cable bundles heading off to customer houses.

Most common, three phase power, is not shown in your pictures. You can learn the basics about three phase power on Wikipedia.
https://en.wikipedia.org/wiki/Three-phase_electric_power

 

[Baluncore]

In Australia we do not use split phase, we distribute 3 phases and have a local Multiply Earthed Neutral, MEN. If you follow those lines to the end of the street and around the corner you will find a transformer, or the end of the lines. Rings are rarely used here as the suburban growth forms a star network and domestic power is not deemed critical.

To balance the load, alternate small customers get N and one 230V phase. The thin bundles of two twisted wires are 1PH supply to a small customer.
Bigger customers get N and all three 230V phases, = 400V, 3PH. The thick bundles of 4 insulated wires are the 3PH supplies going to bigger customers.

The street lights are controlled by a single wire. To test street lights, the area is enabled then they drive along the streets during the day.

In those pictures I see the neutral, three phases, and street light control, with diagonal bundles to customers.
If the jumper clips remain in place, I would look to see if the power has gone underground.

 

[anorlunda]

In Australia we do not use split phase , we distribute 3 phases and have a local Multiply Earthed Neutral, MEN.

@Baluncore has local knowledge which trumps general knowledge.

But lest American viewers try to interpret that, the split phase used in America is done on the customer side of the distribution transformer. Overhead on the poles you will never see a neutral wire. (I know, never say never.) Overhead you will see only single-phase circuit(s) [two conductors each] or three-phase circuit(s) [three conductors each].

And in the American system, there is one distribution transformer for each customer [perhaps 2-3 customers], not one for a whole neighborhood or a whole street.

Reading my posts and @Baluncore 's posts you can also see different strategies in large scale distribution topology: U, ring, or star geometries. Mesh topologies are also used some places.

Once again, this demonstrates how confusing it is to discuss wiring questions on PF where we have global contributors. Practices vary widely, and each poster replies according to his local experience.

Yet another PF Insights article would only serve to confuse things more because it could never include all the schemes used in the home countries of all PF members.

About the only thing we have in common around the world is that the electron is never positive. (I know, never say never.)

 

[Nathi ORea]

@Baluncore has local knowledge which trumps general knowledge.

But lest American viewers try to interpret that, the split phase used in America is done on the customer side of the distribution transformer. Overhead on the poles you will never see a neutral wire. (I know, never say never.) Overhead you will see only single-phase circuit(s) [two conductors each] or three-phase circuit(s) [three conductors each].

And in the American system, there is one distribution transformer for each customer [perhaps 2-3 customers], not one for a whole neighborhood or a whole street.

View attachment 285598

Reading my posts and @Baluncore 's posts you can also see different strategies in large scale distribution topology: U, ring, or star geometries. Mesh topologies are also used some places.

Once again, this demonstrates how confusing it is to discuss wiring questions on PF where we have global contributors. Practices vary widely, and each poster replies according to his local experience.

Yet another PF Insights article would only serve to confuse things more because it could never include all the schemes used in the home countries of all PF members.

About the only thing we have in common around the world is that the electron is never positive. (I know, never say never.)

I think that is incredible how different it all it around the world. You would think there would be one most efficient way of doing things and everyone would do that.

I appreciate everyone's time replying to me so much.

Thanks guys.

 

[Nathi ORea]

In Australia we do not use split phase, we distribute 3 phases and have a local Multiply Earthed Neutral, MEN. If you follow those lines to the end of the street and around the corner you will find a transformer, or the end of the lines. Rings are rarely used here as the suburban growth forms a star network and domestic power is not deemed critical.

To balance the load, alternate small customers get N and one 230V phase. The thin bundles of two twisted wires are 1PH supply to a small customer.
Bigger customers get N and all three 230V phases, = 400V, 3PH. The thick bundles of 4 insulated wires are the 3PH supplies going to bigger customers.

The street lights are controlled by a single wire. To test street lights, the area is enabled then they drive along the streets during the day.

In those pictures I see the neutral, three phases, and street light control, with diagonal bundles to customers.
If the jumper clips remain in place, I would look to see if the power has gone underground.

Is the MEN what is connected to the neutral hole on our power points right? And the Earth hole (bottom one) is the one that gets connected to a copper pipe outside isn't it?

I tried to Google this, but gee.. the lingo. I have so much trouble understanding this stuff.

 

[Baluncore]

Is the MEN what is connected to the neutral hole on our power points right? And the Earth hole (bottom one) is the one that gets connected to a copper pipe outside isn't it?

For a single phase outlet for a customer in Australia and NZ, yes.

The Multiple Earthed Neutral, MEN, is so called because it is connected to Earth stakes at many poles in the street. Inside your distribution box the MEN goes to a “neutral bar”, N. That neutral bar is connected to the 'N' terminal on the top right of every outlet throughout the premises.

Each distribution box also has an Earth stake that connects to the “protective Earth bar”, PE in the distribution box. That PE is connected to the 'E' terminal at the bottom of every outlet throughout the premises.

There is only one place on the premises where there is a deliberate connection between PE and N, and that is a single link between the PE and N bars in the distribution box. PE and N are never intentionally connected inside equipment that will be plugged into an outlet.

The active phase has a service fuse outside the premises before it reaches the meter in the distribution box. (That service fuse can be removed to disconnect the power if you don't pay your bill). After passing through the meter the active goes to a master switch, and then to the “active bar”, A. Active is supplied through over-current breakers to the different parts of the premises, where it becomes the active, A, top left terminal of an outlet. That is the one that bites. It is not unknown for the A and N to be accidentally reversed on an outlet, but that should not kill you. It is also possible for PE and N to be reversed, but that should be detected as residual current through the single link between the N and PE bars.

That is how the three bars, PE, N, and A, in the distribution box are connected through breakers to outlets by three conductor cables. Only the MEN on the poles in the street are connected directly to an outlet without interruption.

During normal operation, the current in A will be equal and opposite to the current in N, and very little PE leakage current should flow. A residual current device, RCD, checks that the A and N currents are equal and opposite.
https://en.wikipedia.org/wiki/Residual-current_device
That can be used to disconnect the circuit if a ground fault occurs.

 

[Chris S]

If the looped wires are for worker safety, I believe the initial question that has been answered by describing the wires as providing a short circuit to protect workers would more accurately, and more specifically, be described as bonding wires, which connect both cables so that any existing difference in voltage between the cables will be eliminated (equalized) by the bonding wires, thus preventing any difference in voltage between the cables that could travel through a person or bird that is too close to both cables as the difference in voltage between the cables attempts to equalize. Any existing difference in voltage between the cables travels through the path of least resistance (the bonding wire) instead of anything or person that gets too close to both cables. I say "too close" instead of "touching" because the very high voltage on the cables can arc between the cable and person without contact.

 

[Baluncore]

I say "too close" instead of "touching" because the very high voltage on the cables can arc between the cable and person without contact.

You can identify the voltage by examining the length of the insulator strings used. The differential voltage between anyone of those lines and ground is 240 VAC, the same as is present at a power point outlet in the house.

 

[anorlunda]

Actually, the shorting straps trigger a trip of a remote circuit breaker in case someone accidentally tries to energize that line.

Residual charges are not the biggest concern. The full voltage and current capabilities of the line in case of accidental energization is the concern.

The most severe electric contingency a power plant can have is to accidentally close the breaker when three phase shorting straps are installed close to the plant. It can set the maximum current interruption requirement for the plant's main circuit breaker.

I remember one incident 40+ years ago when that happened, and the breaker failed to interrupt. The fault propagated back from the high side to the low side and into the isolated phase bus ducts back to the generator. That caused a hydrogen explosion, which broke the shaft, which then triggered a lube oil fire. It destroyed most of the plant. However, if there were any linemen working out past those shorting straps, they were protected.

 

[rbelli1]

the breaker failed to interrupt

How do you test something like this?

It is a breaker that should only trip in case of an insanely bad thing happening. But failing a test (inadvertent or not) causes the whole place to burn down.

BoB

 

[anorlunda]

How do you test something like this?

It is a breaker that should only trip in case of an insanely bad thing happening. But failing a test (inadvertent or not) causes the whole place to burn down.

BoB

Not entirely true. They are meant to trip for much more common events; not just the extreme ones. But there has to be a maximum interruption capability. I don't know how they test the very biggest ones.

No matter how big the biggest circuit breaker, there will always be the possibility of a source with more current than that.The insane contingency is a fault between the generator and the transformer in a big power plant. Currents there can be 25 KA or more. There is no breaker able to interrupt that. Therefore they use "isolated phase bus ducts" as shown in the picture (see the door in the hut to judge the scale). Short circuits between those ducts are exceedingly rare, but if it happens the only remedy is to run like hell.

A more common failure that can burn the whole place down is not electrical, but mechanical failure of the end winding retaining ring of the generator. The first picture below shows a cutout view of the ring. The second picture shows the result of a failure of the ring. I always get nervous when asked to stand close to massive rotating machines. If they suddenly break, there's not even time to run like hell.

 

[Jon Richfield]

The straight connector is a white fiberglass rod that prevents wires swinging and contacting in strong winds. They do funny things here in Australia, the fiberglass rods are also used to support electric fences.

Yippee! That was my guess, and I am not even an Aussie!

 

[Vitina]

I would like to add that this is called a grounded Y system.
The neutral carries any imbalance current.
The size of the conductors and direct connections to lighting indicates low voltage (240 volts to ground, 400 volts 3 phase) system. Ground conductor is separate from neutral because
1. Unbalanced currents will develop a voltage on neutral (this is usually small, about 0-10 volts but can have a relatively large current associated with it).
2. The ground dissipates accumulated static charge and protects wires under it from lightning.
That is 5 wires, 4 insulated (phase 1,2,3, and neutral), (and the separate ground over the top).
Oh, and the neutral is grounded but usually only at the transformer end so as not to carry power current.

 

[Baluncore]

Ground conductor is separate from neutral because
1. Unbalanced currents will develop a voltage on neutral (this is usually small, about 0-10 volts but can have a relatively large current associated with it).
2. The ground dissipates accumulated static charge and protects wires under it from lightning.
That is 5 wires, 4 insulated (phase 1,2,3, and neutral), (and the separate ground over the top).
Oh, and the neutral is grounded but usually only at the transformer end so as not to carry power current.

I would dispute some of that. Australia uses the MEN system, so the centre of the 'Y' is neutral and is earthed at the transformer. Then there is an Earth stake connected to the neutral at every pole servicing a customer.

Single phase customers have different current demands so they generate unbalanced phase currents, those currents return through the neutral where they cancel to some extent.

The 4 wire 3PH 400 VAC street level distribution does not usually have a protective Earth wire above to catch the lightning. In built up areas there will usually be a street light on every second pole. I believe the fifth wire seen on the pole is not an earth, but is a control wire for the street lighting.

 

[Nathi ORea]

For a single phase outlet for a customer in Australia and NZ, yes.

The Multiple Earthed Neutral, MEN, is so called because it is connected to Earth stakes at many poles in the street. Inside your distribution box the MEN goes to a “neutral bar”, N. That neutral bar is connected to the 'N' terminal on the top right of every outlet throughout the premises.

Each distribution box also has an Earth stake that connects to the “protective Earth bar”, PE in the distribution box. That PE is connected to the 'E' terminal at the bottom of every outlet throughout the premises.

There is only one place on the premises where there is a deliberate connection between PE and N, and that is a single link between the PE and N bars in the distribution box. PE and N are never intentionally connected inside equipment that will be plugged into an outlet.

The active phase has a service fuse outside the premises before it reaches the meter in the distribution box. (That service fuse can be removed to disconnect the power if you don't pay your bill). After passing through the meter the active goes to a master switch, and then to the “active bar”, A. Active is supplied through over-current breakers to the different parts of the premises, where it becomes the active, A, top left terminal of an outlet. That is the one that bites. It is not unknown for the A and N to be accidentally reversed on an outlet, but that should not kill you. It is also possible for PE and N to be reversed, but that should be detected as residual current through the single link between the N and PE bars.

That is how the three bars, PE, N, and A, in the distribution box are connected through breakers to outlets by three conductor cables. Only the MEN on the poles in the street are connected directly to an outlet without interruption.

During normal operation, the current in A will be equal and opposite to the current in N, and very little PE leakage current should flow. A residual current device, RCD, checks that the A and N currents are equal and opposite.
https://en.wikipedia.org/wiki/Residual-current_device
That can be used to disconnect the circuit if a ground fault occurs.

Thanks for that. I think that makes sense to me.

It is not unknown for the A and N to be accidentally reversed on an outlet,

Yikes!

 

[Baluncore]

Yikes!

The system is fail-safe since the Active and Neutral inside appliances are both assumed to be live, and so are never deliberately exposed, or connected to Earth. The RCD operates on both A and N, while fuses and over-current breakers operate on the Active, before the wires can get crossed.

When the same domestic equipment is plugged into a 230 VAC outlet in the USA, where there is split phase, both the A and N wires are expected to be live. That is quite normal.

 

[awaygood]

In order to work on high-voltage equipment, that equipment must be (1) de-energised, (2) isolated from any live circuits, (3) earthed (grounded) on both sides of the equipment to be worked on, (4) protected by some form of barrier with notices indicating danger of high voltage, and (5) a 'permit to work' issued on the technicians, giving exact details of what is to be done. What you see in this photograph is the protective earthing conductors attached to the de-energised and isolated conductors on one side of the equipment.