Why there is no Neutral in Transmission Lines? Explained | TheElectricalGuy

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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

rizwanullahzahoor

😮😮
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 😮

bhishmakaliyuga

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.

ccshello

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.

heronimousbrapson

He is right and he has also given the main reason why there is no neutral wire congratulations 🎉🎉

erastuskariuki

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.

nicolasuribestanko

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.

abuaymanassalafi

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.

davidh.

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

wanlambokshadap

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.

jamesspash

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?

GianniDoriaRuotti

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)

erickmartinsmxusca

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.

paulromsky

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.

petehiggins