Why there is no Neutral in Transmission Lines? Explained | TheElectricalGuy
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- เผยแพร่เมื่อ 22 พ.ย. 2024
- Understand why there is no neutral provided in transmission line and why we need neutral in distribution. Electrical interview questions.
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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..
This is 100 y. old system, now you have DC lines + and - and iinverters. Where do you live ? Why you have this old system ?
DC system has a lot of advantages. pLease switch to modern tech. not this 3F for apes. It is a shame.
😮😮
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.
And also in Distribution side he was not provide Graph and explain it unbalance current phenomenon
In few words.
Because in a transformer the 3 phases are coupled magnetically.
Sharing what I know/learned:
- The long distance transmission lines for a power distribution systems are 3-phase "3-wire" systems. These power grid designs are for efficient power distribution and at the same time, save cost.
- There can be additional thinner lines situated at the highest points on the tower. They are mainly for lightning protection. These wires are too thin for neutral (N) line as return path.
- The steel tower structure itself is grounded locally for Protective Earth (PE), but it is NOT for alternative path for Neutral. The earth (soil, rock, etc.) is never intended for Neutral "N" return path nor for 3-phase power imbalance.
- 3-wire transmission line with no real physical Neutral wire in existence, I would call it a Delta system.
My 2 cents.
He is right and he has also given the main reason why there is no neutral wire congratulations 🎉🎉
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.
Is the earth literally used as a return path or is it more like a capacitor that stores and returns charge cycle to cycle? I ask because we have SWER in my neighborhood and it seems like a long, long way back to anyplace where there might be a neutral. I've never understood this and am hoping you can answer or point me to more details?
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.
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
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)
The return path is the other phases. Just as a 240v appliance doesn't need a neutral in the USA. When one phase is positive, the other is negative. In three phase, the same happens but distributed across the three. He really didn't explain it correctly in reference to neutral.
In split phase (USA) you need the neutral to return power used in an imbalanced manner across the two phases (which are 120v potential) one uses a light bulb and another phase uses a dishwasher for instance. If you neutral goes open, the imbalance can return 240v into a 120v appliance.
Moreover, in Europe, single phase is different. You have a hot that is 240v with a neutral that is zero.
I wish someone would have explained this to us the simple way like you did, Gauravji....
Renewed understanding key concepts:
1. Transmission n/w
2. Distribution n/w
3. Balanced/ Unbalanced load
4. Netral wire concept
Perfect explanation! 🎉 he emphasized the need for a balanced circuit to not have a neutral line.
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.
This happened to our neighborhood during the previous large geomagnetic storm. I have a server farm and have a lot of monitoring systems and our voltage went up to 300 volts on one phase and caused some damage throughout the neighborhood. It tripped over half our breakers but the main breaker did not trip since the over voltage only existed temporarily.
That day was insane (weekend).
My schooling taught:
(for long distance transmission) =supply end as Star to provide centre-tap for earth purposes only;
the downstream transformer as a delta winding as there’s no supply neutral anyway
Your explanation Sir was EXCELLENT. Thank You !
Glad it was helpful!
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.
Exactly. But since its a single phase transformer ( using only one phase at the primary ) , it automaticaly unbalances the high voltage lines.
very comprehensive. good job 👍
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.
Some notes. What you call "Star" is commonly known as Wye 'Y' configuration. It uses 3 phases with a Netural in the center. You really didn't show the the 3 wire configuration known as "Delta", there is no Netural in a Delta (triangle) configuration. Both configurations transfer power equally, but for long distances the Delta is used to save the need for a forth cable (cost savings in that case). Transformers are used to convert Delta to Y so that different phases and voltages can be used. The Delta can only power 3 Phase equipment (which only factories have), but Y can power (in the US) 3 phase 208V, split phase 240V, and single phase 120V all from a single Y secondary. The Netural is normally tied to ground at the Transformer and again at the home as it enters the breaker panel.
I was confused at first then the light bulb lit up when you explained the houses being unbalanced. Thanks!
Thanks for adding actual subtitles for the Deaf
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)
THank you for the excellent explanation.
Found this explanation useful as I'm preparing to enrol for PhD or Ms in Electrical Engineering
all the best!!
Thank you so much for the explanation :)
Can 5:14 be used to conclude that neutral in the socket "is neutral" because it is connected to all 3 phases?
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.
The reason is that the distribution system always feeds into a balanced load, ie, transformer windings.
Very interesting explanation
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."
Great job explaining this…..
why didn't you say anything about the return path of the current and N's role in that? sorry but also what does the "balanced" mean that you keep saying ?In your example of the houses you explained this differences in Current (Amps). So are we trying to balance current or voltage here?
Excellent work.pls make video on surge impedence loading of transmission lines
Good, informative video!
Great video, very good, thank you Sir! 😊
I would add ... in the high voltage lines ( 420 KV ), the currents are not so hight ( Power = Voltage x Current ), and any difference ( or algebric sum ) among them is far more little ...
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.
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.
well and simply explained !!! thank you
Glad it was helpful!
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'm used to looking up and recognizing the wye configuration for secondary output of residential transformers. One day I looked up and I think I recognized a delta output from a pole transformer going to an auto shop. How do they manage to get a neutral wire to serve the shop from a delta configuration? Was I mistaken?
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
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.
Thank you so much...very informative,
Glad it was helpful!
Good explained
Glad it helped
The exact topic i was thinking of today!! 🤯
Adding a neutral would be a waste of wire, because no current would flow in it. That's because if significant current did flow in the neutral it would only happen if the loading on the phases was unbalanced, and therefore suboptimal use was being made of those 3 conductors too.
Great video good explanation
So if a single line of threephase delta hvac is cut and the hot sidetouches the ground, i wont get shocked since theres is no connection with other phases and no neutral grounded like a star connection
Thank you for educating me!
if secondary is unbalanced how can primary be balanced? ;)
Because primary is the main power station, secondary is distributor end at the sub station, so even if the secondary means substation unbalaced , the primary means power station doesn't effect.
6:40 Neutral is needed in distribution system because it is not balanced=we can not control the load
Looks like your drawing of P and S above the R line at the 2.12 min mark were incorrect. Primary is on the left not the right side and vices Versa.
Nope. He mean primary side of the shown secondary and vice versa. He's actually correct
Electrical infrastructure is becoming critical for civilization, obviously. When everybody has a clear understanding we can make good decisions.
Awesome video! does that also go for sub-transmission lines (66kV)?
Transformers are in star. Phase to phase 440v. Phase to star point 240volt.
In addition, faults also register as phase imbalances, so in addition to ground return faults the protective devises also watch phase imbalance.
But why is a circuit that is unbalanced on the secondary side (distribution line), balanced on the primary side (transmission line)? I understand that they are independent of each other, but how?
Sir why did you took
R phase =0
Y phase =-Imax
B phase = Imax
Please teach this
sir in sending and recieving end in transmission t/f neutral grounding is done or necessary?
How much current on the neutral in the given diagram?
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.
At 4:30, it looks like a circular argument. You're saying that the currents are balanced, BECAUSE the currents are balanced. The voltage waveforms are depicted, but does that mean the current waveforms are also balanced? But what if they are not balanced? Is that possible? Can an unbalanced load on the secondary of the downstream transformer cause an unbalance in the transmission line? I'm kind of thinking that BECAUSE there is no neutral, the currents are naturally balanced. Any "excess" or "shortage" of current in any phase is carried by the other 2 phases. In other words, the transmission line is self-balancing because, as you said at the start, the transmission lines are electrically isolated from the source and loads, and that's OK.
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
The simple reason transmission lines are delta with no neutral is, If there is a fault to ground, the fault current returns through the earth and the grounded static line if provided to the source station where it is a grounded at the a source transformer via why out put configuration or a delta grounding transformer to sense the return current and to trip the source breaker. Simple.
Is the imbalance current flows through earth via neutral ? or only the earth fault current flows through the earth.? please explain.
Which size of cable using in Transmission line?
Sizes are mentioned as rabbit, wolf, panther , zebra, moose etc as per size
Very nicely explained, thank you
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.
So we can use star connection without neutral?
In 11KV , I have seen no neutral, but before substation why there are 6 wires?
And at distribution (step down) transformer, how the neutral line is introduced, please explain the connections
Neutral line comes from the star point of the transformer which is grounded at the transformer.
Enlighted by your analysis of this.Thanks.
what if the delta connection of transformer,are they having a neutral wire to comnect ?
If the distribution network is unbalanced, wouldn't the uneven loads between phases cause an imbalance in the transmission network?
I asked the same question.
Logically, i think it does.
From what i know, the power company uses the earth and also a wire on top of transmission lines poles tower as a return path to the main generator to even charges.
The wire on top of pole towers is grounded, and his main purpose is to protect the power lines from getting hit by lightning. And also, if an airplane or helicopter happens to fall on the wires, it will hit this wire first.
@@martf1061The earth wire on top of Extra High Voltage line is only grounded . It does not provide any return paths. Yes the phases stay unbalanced in a line slightly but since the grid network is interconnected, it gets balanced.
if secondary is unbalanced how can primary be balanced
Because the transmission circuit is electrically isolated from the distribution circuit. The first thing he said.
Hi Sir, your videos are very helpful and informative, please also make a video about neutral ground resistors. Thank you sir
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.
THANK YOU
Thanks very much.
How about PE / Earth conductors, why is it not needed in transmission?
How can you say that Iy and Ib are maximum at the same time . Whereas they are 120 seperated.
Star delta configuration is always used. If lighting current enters the line how it get earthed if it is deta delta configuration.
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
Hi Gaurav, your videos are great. Please do a video about Transformers vectors group and why we need them.
Thank you. Sure. Will try
Please sir can you work a video on " difference between grounding and earthing ".....i got confused on it !
there is no difference , you asking like what is the difference between india and bharat or hindostan,
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.
In Australia the only place you will find a neutral wire is between the low voltage transformer and the customer.
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.
You do not connect them. You use transformers.
Thank you, GJ.
High voltage transmission lines do not use Y scheme. They use exclusively delta configuration, thus system is balanced, and neutral does not exist.
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.
Please be aware that in the UK phase colours changed to Brown, Grey and Black with the neutral now blue many years ago.
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
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...🤔
There is a neutral in Wye secondary generated electrical systems. Allot of generated electricity is Delta - Wye.
Thanks, you answered the exact question I had in mind!
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!
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.
thanks very good explained with quality.
Glad it was helpful!
The diagram does not show max or min unless slight lag between voltage and current?
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
what about DELTA connected Transmission Lines?