Why there is no Neutral in Transmission Lines? Explained | TheElectricalGuy
Vložit
- čas přidán 23. 08. 2023
- Understand why there is no neutral provided in transmission line and why we need neutral in distribution. Electrical interview questions.
Course on Transformer - courses.theelectricalguy.in/c...
Electrical courses ➜ courses.theelectricaalguy.in
Importance of Neutral wire - • Can we remove Neutral ...
===============================================
📌 Join me on Social Media
Facebook ➜ / iamtheelectricalguy
Instagram ➜ / the_electricalguy
===============================================
#electricalinterviewquestions #neutralwire
Ohh my god the way you explained.... Thank you so much
Happy to help
Fantastic Explanation.
Yes. That’s right in case of distribution network. In the video i am specifically talking about the transmission network..
😮😮
The correct explanation is, In 3 phase delta (or star without neutral) circuits, no need of neutral as return path. Because, the return path for the each Line current will be provided by reaming two other lines 😮
Exactly
And in residential connection neutral is required as almost all of our domestic appliances require 240V to run that is the phase voltage or the voltage between neutral and phase.
There isn't a neutral on the high voltage side for most single phase residential distribution in the U.S. The neutral that comes into the house is actually a center tap of the secondary side of the transformer winding. This gives us two opposite phases of 120V from each side of the secondary winding to the center tap, which is neutral. Across the entire secondary winding we get 120V + 120V = 240V, which we use to power higher power loads like stoves, clothes dryers, A/C compressor motors, etc. So the neutral in the house is just a construct of the center tapped secondary and is referenced to ground.
Here in western Canada, it is common to see three phase and single phase distribution lines in rural areas with no neutral wire; the earth is used exclusively as the neutral conductor. The single phase lines of this type are referred to as SWER - single wire earth return.
Plenty of SWER in South Africa and Namibia. South African development in th 90s. Pleased to hear they are using it in Canada.
And in AU
Same in Brazil. Very common, specially in remote areas, where power demand is low. Otherwise, 3 phase distribution system is the norm.
On single phase distribution, two wires are used. The top wire is usually the neutral and is grounded. If you trace it back, it goes back to one of the 3 phases and the neutral. The grounded neutral provides some lighting protection and when things like tree branches fall and break the lines, the grounded neutral will drop and contact the live phase wire tripping protection devices like fuses or upstream breakers. Thar tends to keep live wires from hitting the ground posing danger.
When the first telegraph lines were installed (about 1840, between Washington and Baltimore, I believe) they used a neutral wire to complete the circuit. Then they discovered that the circuit could be completed through a ground connection. This enabled them to use the return wire for additional communication.
Sort of, but telegraph lines were not 3 phase. They were DC. In that, the so called "neutral" was just a return and not a true neutral.
Transmission lines typically carry high-voltage electricity over long distances. Since transmission lines primarily transmit power from generating stations to substations, they operate at very high voltages, often ranging from hundreds of thousands to millions of volts.
In such high-voltage systems, the primary concern is to minimize energy loss and maximize efficiency. Neutral wires are not typically required for this purpose, as transmission lines are designed to carry balanced three-phase AC power. Additionally, the high voltage levels mean that any return currents can flow through the ground or other conductive paths, eliminating the need for a dedicated neutral wire. Therefore, transmission lines usually consist only of three phase conductors without a separate neutral conductor.
Ibn taymia discovered that?
Technically, there is no energy loss but there can be an electrical power loss.
@@georgejetson4378 Considering power is simply energy/time, that's a bit hard to support.
@@stargazer7644 Energy unlike power is conservative.
Perfect
Thanks for adding actual subtitles for the Deaf
Great video! Just one question. The secondary part of the distribution transformer is feeding an imbalanced load, therefore it needs the neutral to carry the imbalance. We also know that the load on the secondary of a transformer directly impacts the load on the primary due to the interactions of the magnetic fluxes. If this is the case, how come that we dont see an imbalance on the primary side aswell?
He explained it wrong. How can you balance the load? They cant. Only the end user, like a motor or heater with the same resistance on each fase.
Search for Delta Wye Substation. The solution is in the substation transformers. They are not just 3 separate transformers.
You do see an imbalance, except it doesn't only load one phase like the star secondary. The imbalance will appear as greater load across two phases on the delta primary. This is the same as if you were to disconnect the neutral line's tie from the starpoint of the transformer. All the single phase loads will draw from one phase, go onto the broken neutral, travel through another load and back to another phase.
(Of course you're now dividing line voltage unequally across differently sized single phase loads, but the analogue stands)
Thank you for educating me!
The actual reason there is no neutral on a transmission line is, If the line was run in a Y configuration over all to all smaller distribution sub stations,, there would be many ground return paths, through each substation along the line. And the energy return to source station distribution would be reduced. With the delta, no neutral configuration, all faults current is returned to the source station, through the earth ground and via the static/lightning line if equipped. To where there is fault current detecting equipment installed trips out the source of the transmission line. The fault current is returned to the source location to cut off the source. Like the breaker panel in your house , sort of. There is a ground source reference at every source transmission station. Transmission lines, some wired like Y configuration at the source station., but grounded at the source station only with sensing equipment on the ground. But exit in a delta. Some delta only stations have what's called a zig zag bank transformer or ground reference transformer. The CT's and VT's of the ground ref unit are connected to the protective equipment to shut down the line if there is a phase to phase fault or phase to ground (tree, downed conductor,car accident) issue.
Good explained
When there is no neutral then the currents are balanced by definition. They have to add to zero by Kirchhoff's laws but if the load impedances are not balanced then this only happens by the voltages across the three phases adjusting themselves. So if the loads are not well balanced then the three phase voltages will not be the same. In order to limit the imbalance in phase voltage and keep them in spec. the loads on each phase have to be distributed roughly equally between the properties. There are occasionally faults where the neutral connection to a local area goes open circuit and the result is out of spec and often damaging over-voltages appearing in peoples homes.
Excellent work.pls make video on surge impedence loading of transmission lines
Thank you so much...very informative,
If you have 3 phase power supply in your house, which is common in Europe and other places I believe, you can plug some devices that don't use the neutral wire at all. And they will work perfectly fine. One of them is a 3 phase motor. If you wire the windings in a delta pattern, you just hook up 3 phase wires to it and the neutral is completely not needed.
Very nicely explained, thank you
I was confused at first then the light bulb lit up when you explained the houses being unbalanced. Thanks!
well and simply explained !!! thank you
Glad it was helpful!
There is no neutral on transmission lines because it’s not needed. We don’t connect loads phase-neutral at the bulk electric level.
Distribution uses a neutral because it allows loads to be connected phase to neutral, which is also lower in voltage due to how a wye - grounded connected transformer works (about 57% lower, factor of rad 3). It’s also cheaper because you don’t have to insulate equipment to the same level as phase to phase voltage. A neutral wire also provides a low resistance path back to the substation transformer for faults. Since most solidly ground systems with neutral conductors also ground the neutral out in the field on the poles, if a wire falls down on the ground the current only has to travel the distance to the nearby grounded pole.
Transmission does have grounding at the substations for ground faults. It’s either done with grounding transformers or auto transformers that are grounded. Those grounding points are the return for a line to ground fault on a transmission line.
I have a question. I need to operate a waterpomp(2Hp/ 1 phase) at a distance of 100m on my land for agriculture. Can I use one single wire for load and at the end use a grounding wire that is connected to a 10 ft copper earthing rod on the spot as Neutral wire? So I don't have to use double wire for the 100m distance.
you can but dont use any earth protection device only u can use one switch for operation.
There are no L-N loads at transmission voltage. L-N loads downstream of transformers fed by transmission becomes unbalanced 3 phase current, I2, in the transmission circuit. Utility generators have I2 limits, so the utilities try to keep their LN loads equally loaded on the phases to keep I2 back up at the generators from getting too large. Note, unbalance does not cause neutral current, I0.
The diagram does not show max or min unless slight lag between voltage and current?
The exact topic i was thinking of today!! 🤯
Thanks, you answered the exact question I had in mind!
The three-phase star transformer is just 3 independent single phase transformers. The red primary only cares the currents on the red secondary. Let's take the extreme case where only the secondary of the red phase of the right hand transformer has a load and the other two secondaries have no loads (no current). Then the currents in the three right hand side primaries are certainly not balanced. Stating that the circuit you have drawn is 'independent' just means that it is floating, ie: the absolute voltages with respect to ground could be anything. It doesn't mean that it is balanced, and no actual explanation is given for that assertions. I am guessing that the star points at each end are grounded in actual transmission lines. I must be missing something here. Please enlighten me.
But how do you connect balanced transmission line to unbalanced distribution line? Where do you connect N in the unbalanced distribution line? To the ground? Then we still have 4 lines in the transmission line: 3 wires and ground that carries N.
What’s the thin wire at the top of the pylons for, please? I’d always thought that was the neutral which could be light because it wasn’t carrying much current. Is it just a lightning conductor, then?
It's not the neutral wire and it's not connected to the transformer of that high voltage line. That's a shield for the pylons against lightning strikes. They are grounded for this reason. Some of them are OPGW cables (optical ground wires) and are made of optical fibers in the center, surrounded by steel and aluminum. It provides communication between electrical power plants.
Thanks, that’s clear now.
If the distribution network is unbalanced, wouldn't the uneven loads between phases cause an imbalance in the transmission network?
at around 5:11 you state from the graph that the current shown is zero when in fact this graph is showing voltage not current. So the voltage is zero at 360 and if no voltage, then there is no current. Semantics but the graph is VOLTAGE over time, nothing shown indicates what the current is.
in the Primary distribution (high voltage network that leaves the substations for the distribution transformers) there is also no neutral, there are only the 3 phase cables at the top of the pole, because in the high and medium voltage, energy is a circuit isolated by transformers, requiring neutral only in low voltage (or secondary distribution)
We can also calculate the value of the voltage with this equation v(t)=Vmaxsin(ωt+θ), knowing that phase two is shifted by 120 degrees relative to phase one, and the third phase is shifted by 240 degrees relative to the first; the sum gives zero."
Curious as to why you did not mention the neutral and Earth connection at the center point of the transformer on the distribution side.
Isn't integral to the explanation he is giving. Yes you would have your N to Ground connections to prevent floating voltages
Very good question!
Actually, mid points of stars on both sides can be grounded, and earth can play the role of neutral wire. But this is not usually done for the purposes of protection. Having grounded mid points and neutral wire is the best option
Electrical infrastructure is becoming critical for civilization, obviously. When everybody has a clear understanding we can make good decisions.
many thanks plz need to explain how as example in 11 kv lines with no potential difference and how different in the phoser works
I have seen lots of distribution lines that are delta connected with, of course, no neutral. Some power companies use them a lot, and they used to be more common years ago. So I would not say that a neutral _must_ be used, but rather that a neutral is desirable for distribution lines. I’m not an electrical engineer, but I imagine that a distribution line with no neutral would need to be derated to a lower power carrying capacity than a similar line with a neutral, and also that more attention must be given to load balancing when designing the distribution network.
3 phase incoming to DB, incoming to contactor, contactor to 9 mcb..my friend and I wanted to connect single phase to mcb.. We use the last mcb (which is the 9th mcb), switch position to off and connect live to mcb terminal.. Here is where I do not understand.. All other 8 mcb is live and neutral is connected to neutral point and my friend just use his bare fingers to open one of the nut on neutral point to connect our single phase connection.. Till this day I still do not understand why he doesn't get shock by touching the neutral.. Can you explain why sir?
because no current flows thru hm
Why is the transmission line balanced ? If a phase has a different load on the distribution network it should reflect a different load on the respective transmission phase, causing an imbalance. I believe it does cause different voltages in different phases if no neutral is there. I think it is called a neutral shift and can cause problems. However, power can be distributed such that an unequal load is unlikely. For example a large industrial power consumer will have a balanced 3 phase load on the distribution network. Consumer homes likely present a small load. However, if all the people in homes on the R phase decide to use the washing machine at the same time, a neutral shift will happen and might cause problems.
How about PE / Earth conductors, why is it not needed in transmission?
Thank you Sir
How much current on the neutral in the given diagram?
how can be balanced transmission line when the distribution side is unbalanced.?
I think of a caveat. If the distribution transformer is composed of 3 separate single phase transformers, as sometimes is done, then the transmission line would have to incorporate a neutral conductor or at least utilize ground path to transfer unbalanced power. Otherwise voltage on the unbalanced load will collapse
Question…if increasing the load on the secondary or a transformer also causes an increase in current on the primary of the transformer. Why would there not be an imbalance on the primary side going to the substation is the secondary side of the three phases leaving the substation could have an unbalanced load? Or am I misunderstanding how a load on the secondary effects primary current in a transformer?
Load on the secondary does not affect the primary!! Ps - yes there will be an impact on the primary due to changes in the load on the secondary.
@@GauravJ Thank you for the reply. I’m just still a little confused since prior to this video I have read as well have seen videos explaining the effects of secondary current and secondary back emf actually cancelling some of the primary windings back emf which in turn causes an increase in current in the primary winding. It seemed to make sense and now I am learning something else that is new so I am just trying to make sense of it. It seems as though there are some transformers where the secondary affects primary current but in the case of three phase high voltage transmission lines to a substation it is not the case? Not sure if having secondary neutral and primary neutral bonded makes any difference or not (referring to single bushing transformers supplying power to homes here in the US) i’m not doubting you so I’m sorry if it’s coming across that way, just trying to learn. Seems as though the more I learn, the more I realize how ignorant I am lol.
@@GauravJ If I have a simple transformer and the secondary suddenly draws more watts because of increased load, wouldn't the primary also be supplying an increased amount of watts? So if the distribution side secondary has different loads on the respective phases wouldn't that translate to different loads on the respective primaries and make the transmission side unbalanced?
I totaly agree, when there is a fault on the secondary side of a transformer, that fault will reflect as a high current also in the primary side causing its protection cut out assembly to disengaged. Thus secondary load changes affect the primary circuit of the primary. This is true for every transformer, single phase or three phase,low voltage or high voltage,however in the distribution side,which is a wye configuration,the utility company make sure that load distribution to each phases are balance as possible as they can to minimized imbalances, it will not be perfectly balance since the use of every household,commercial and industries are variable. However placement of transformers particularly single phase are arranged in a manner to minimized imbalances back to utility main three phase transformer.the utilit transformer is usually configured delta primay at 69kV for example while its secondary is wye at say 13.2KV with grounded neutral for single phase loads and will carry the minimized unbalance current back to utility transformer. This minimized unbalance load will have very small effect on the 69KV delta side of the utility transformer, and basically this 69Kv is supplied by powergrid say 230/69KV transformer which has wye-delta configuration. That any minimized imbalances at the 69KV will be even minimized further down back to the generating stations by the succeeding high capacity power transformers.Hence for the wye configured 230KV side with no neutral conductor along those line currents are almost balance, The high Line voltage will even make the imbalances if there is such to have insignificant effect on the three phase voltages even there is no neutral conductor connecting the two sides of the distant transformer of the power grid and the distribution or the utility company. The higher the transmission voltage the better to use wye with no neutral to save coil insulation for the transformer due to line voltage divide by square root of 3, rather than a delta configured that the phase voltage will be equal to line voltage hence it will require thicker insulation for the coils. This are only few considerations in the design to use wye or delta in the high voltage transmission lines. So wye or delta can be possible configuration in high voltage transmission lines because the three phases are almost balance in terms of their line currents.
Interesting that you explain how the currents sum to zero by using a voltage vs. time diagram for the 3 phases. For clarity, you should have used a Current vs. time diagram instead.
Please sir can you work a video on " difference between grounding and earthing ".....i got confused on it !
Thank you
Have been looking for this for 3 years.
My local distribution also has no neutral. All of the RESIDENTIAL
single phase step down transformers have ONE BUSHING and no observable neutral wire back to the substation.
Every transformer (along the line of one of the phases)) is NATURALLY connected to ground from the transformer can.
Comment please.
The neutral is almost certainly strung along in the secondary space, with the services and secondary conductors. It may not be at the top of the pole with the other primary equipment.
@@req44 Well, it is clear to me. Only one conductor running at the top of the pole.
Many many single phase step down transformers being connected to this SAME one conductor. Naturally each can is connected to earth coming from a COMMON POINT
inside the transformer.
AKA multi point grounding system. Still looking for this mysterious neutral
conductor ( which is not evident)
comment please
Post a picture of the poles and I'm sure we'll find the neutral. Electricity doesn't work too well without a return, and the earth, as good as it is, can never be relied on to replace a conductor for regular use.
My friend, check-out SWER systems (single-wire earth return) and I reckon you shall find the answer you are looking for. Hope it helps from a fellow electrical engineer!
Found this explanation useful as I'm preparing to enrol for PhD or Ms in Electrical Engineering
all the best!!
Surely you still need to load each phase as evenly as possible, else you're going to have wildly different currents in each phase. Yes, it's balanced, but the maximum capacity can't be achieved unless the currents in the three phases are equal.
Since load and source are connected with transmission line, if load is unbalanced in power system does it also makes lines unbalanced or not ??
No. It does not.
In addition, faults also register as phase imbalances, so in addition to ground return faults the protective devises also watch phase imbalance.
Hello sir! I would like to ask you a question about Parallel transformer. How can 2 transformers be parallel to each other? And how many point it can be parallel?
hello your questios make no sense pls try again
Star delta configuration is always used. If lighting current enters the line how it get earthed if it is deta delta configuration.
High voltage transmission lines do not use Y scheme. They use exclusively delta configuration, thus system is balanced, and neutral does not exist.
Who connect secondary with primary through neutral. It's only we connect secondary coil in star winding pattern and from all RYB connected point, we take neutral conductor.
We have a 110 kV railway power line here. One circuit has two conductors!
There are two circuits on the mast, so four conductors.
At the other end is a transformer with one primary and one secondary winding. No three-phase network.
The railway then runs to ground at 15kV 16⅔ Hz
Sir i have a doupt. In between the transmission line there is no neutral because its a delta connection, but if any fault comes in the transmission line like transient what will happen then
the circuit breaker will open that circuit.
Thanks. Good information for a learner of electricity
Thanks for watching
Sir do you have any course for How to read the schematic drawing
we have a course on circuit breaker control schematics. Below is the link -
courses.theelectricalguy.in/courses/Circuit-breaker-control-Schematics-Masterclass--Beginner-to-Advanced---647b08bce4b08fb4470c3021
You get 3 windings. What you do with them is up to you.
Many of the comments express thanks for explaining why 3 phase transmission does not require a neutral wire . ( see 2:07/8:45 ) But I wonder if these people understand that in the
920 Kv TRANSFORMER : the current of RED phase flows to the PRI ; that current is returned from the PRI back to the YELLOW and Blue windings of the 920 kv transformer
YELLOW Red Blue
BLUE Red Yellow
Good video, thank you for sharing
Glad you enjoyed it
Hi Sir, your videos are very helpful and informative, please also make a video about neutral ground resistors. Thank you sir
good
Thanks for making this video!
Glad it was helpful!
Please be aware that in the UK phase colours changed to Brown, Grey and Black with the neutral now blue many years ago.
Thats how we know how far out from the source station the issue is. Phase A to ground. 8 miles. Or phase AB. 6 miles. Trees normally.
The reason is that the distribution system always feeds into a balanced load, ie, transformer windings.
But in transmission, delta to delta will be used sir. So no neutral. Is it not correct explanation?
It is not necessary to use only the delta delta connection in transmission ..
thanks very good explained with quality.
Glad it was helpful!
I love Gaurav's videos!!!!
An asyncron motor is connected with three phases and grounding for the housing.
But there is no neutral.
Thank you for sharing such valuable information sir! Would it also be possible for you to share your knowledge about Open Delta (V-V) and Open Wye - Open Delta Connections? Hoping for you to notice my comment and make a video about the topic I mentioned. 😁
Sir I want to join ur circuit breaker course...but it's bit expensive...any offer coming in future???
Great video sir.
I have a doubt like if at genaration side if generator armature winding is star than neutral is not used there also?,or what?
because that voltage also will be stepup by transformer
So my doubt will neutral from generator to stepup transformer be connected or not?
Transformers are in star. Phase to phase 440v. Phase to star point 240volt.
There is a neutral in Wye secondary generated electrical systems. Allot of generated electricity is Delta - Wye.
The return is via earth.
Thanks, Gaurav for a great talk
Superb explanation, thank you sir 👍
You're most welcome
I thought that for long distance transmission, the delta configuration would be used, and then at the substation after stepping down the voltage, it would be converted to a star configuration for distribution.
My thought too...🤔
The structure metal is grounded as underground lines..., I suppose, there U have your neutral. It will make a fase neutral short circuit.
Hi Gaurav, your videos are great. Please do a video about Transformers vectors group and why we need them.
Thank you. Sure. Will try
Nice ,,well done sir
Thank you 😊
The transmission line is three phase so there is no neutral wire.
Thank you for the explanation
Glad it was helpful!
Surely such transmission lines are Delta connected, only to be transformed to Star
at the local sub-station, thereby not using a neutral and saving cable cost !
Transmission 115 kv and above Y
does long distance transmission have delta connection wire configuration and short distance transmission line have star connencted configuration?
This is incorrect. In the US, transmission lines are delta connected, not Wye. There is no grounded conductor. Distribution transformers are delta-Wye. The secondary of the distribution substation transformer is Wye connected and the center point is grounded and becomes the neutral connection. The distribution neutral may or may not be run to each pole. At the final pole transformer for a residential service the primary wire is connected to the primary winding and the other end of that winding is grounded
On the secondary side of the pole transformer, two “live” wires go to the house. These are 240 volts. A third wire that is the center tap of that secondary winding is grounded at the pole and at the service entrance to the house That becomes the neutral wire for the house.
This is what is called a multigrounded secondary service which is the most common in the US.
For commercial three phase service three single phase pole transformers are normally used connected with their primary windings in Wye with a grounded neutral and secondary windings also Wye connected with a grounded neutral.
It's not true the load conected on the secondary of a transformer will not impact the primary currents.
What will happen in case of Earth fault?
Thanks sir 👍
wow what a explaination
People are shocked when they learn I'm not a good electrician.
Poor electricians are shocking for sure. Their families are often energized.
What country?
explanation provided here is wrong load imbalance on secondary side will indeed effect the primary...
the exact reason why we don't see neutral on High voltage transmission is because those set of wires are Delta comnected.
Which configuration? ΥΔ, ΔΔ or ΔΥ?
@@MultiSigen Y∆ with generation in star and transmission in delta , it can be ∆∆ too with generation in delta and transmission also in delta
transmission is generally in delta
Exactly my thought .. so now am behind with the explanation above...🤔
Well, the whole reason we can use delta connections is because the load is balanced!
Why we have not found shock by neutral
Am I missing something? At 360º Iy≠-Imax and Ib≠I max just by looking at it.
It was just an example for understanding. But even if you take the actual values at 360 degrees the sum will be zero.
@@GauravJ Ah ok. I got a bit confused there. It might be better, if using 360 as an example to put amplitude as Imax*sqrt(3)/2 to avoid confusion. But you are right, the add up to zero.
Exactly, if at any time one of the phases is 0, neither if the other two can be max. It was an unnecessary simplification causing more confusion.
Transmission network - no neutral, what about sub-transmission networks?
Not required there as well
Nutral is not just for balancing the loads. Its important for return current to the source. To complete circuit. Thats why nutral is grounded at the transformer side. To provide easy path for current with lowest resistance to back to the source. At Distribution side of course.
thank you brother
Very nice
The neutral doesn’t “ balance the loads” … if the loads are equally loaded you do not require a neutral at all. In a balanced system minus & plus values are equal so the neutral conductor will equal zero at all times.
The neutral carries the remainder of the current in an unbalanced load. As per kerchov law that states what goes in must equal what comes out.
The path of least resistance is the neutral, the general mass of the earth has a variable resistance & the neutral is a constant connection of a set resistance they don’t even compare in resistivity. So if you are waiting for the star point to earth to become the “ path of least resistance” then you have a very long wait before its value beats the neutral. SMH.😂
@@goaway9487 You cant balance the load. How wil you do that ? This only works ive you for sure the users only use balanced machines, like motors. But that never will be the case, only in end users line. The earth is the nul line, he explained it wrong
Search for Delta Wye Substation. The solution is in the substation transformers. They can do a bit of balancing.
But engineers have to balance single phase going to subdivisions periodically to ensure the load is mostly balanced across the three phases.