The Electrical Grid and Electricity Supply | A Simple Explanation

Summary

This video explains how power grids work, detailing the main components involved in transferring electricity from power stations to homes. It covers the three key stages: generation, transmission, and distribution, and explains the importance of transformers in reducing power losses by increasing voltage and decreasing current. Viewers will learn how transformers, substations, and transmission towers function to efficiently deliver electricity over long distances, and how different voltages are used for various consumers. By the end, you'll understand the workings of power grids and how everyday electrical infrastructure operates.

Takeaways

• ⚡ Power grids consist of three main sections: generation, transmission, and distribution, with consumers at the end of the grid.
• 🔧 Power generation doesn't create power but converts energy from other sources (e.g., coal, hydro, wind) into electrical power.
• 🌡️ Power loss occurs due to the resistance in conductors, generating heat, and is mitigated by increasing voltage, which reduces current.
• 🔋 Transformers are critical to increase or decrease voltage, helping reduce power losses and allowing efficient long-distance power transmission.
• 🔄 Transformers operate through electromagnetic induction, transferring power between coils without direct contact and only work with alternating current.
• 🏗️ Transmission towers carry high-voltage lines and are designed to keep conductors far from the ground and other objects to prevent electrical arcing.
• ⚙️ Substations manage voltage changes, protect the grid, and allow sections of the grid to be isolated during faults or surges.
• 🏠 Step-down transformers reduce voltage as electricity gets closer to consumers, ensuring appropriate voltage levels for different types of users (industrial, commercial, residential).
• 🛠️ Substations and transformers help maintain grid stability, protecting equipment and ensuring reliable power delivery across large distances.
• 📡 Power grids are complex systems that depend on multiple components working together to ensure safe and efficient delivery of electricity to homes and businesses.

Q & A

What are the main components of a power grid?

The main components of a power grid are generation, transmission, and distribution. Additionally, end consumers are sometimes considered a separate component.

Why is it incorrect to say that power stations 'generate' electrical power?

It is incorrect to say that power stations 'generate' electrical power because, according to the law of conservation of energy, energy cannot be created or destroyed. Power stations convert other forms of energy, such as chemical, kinetic, or potential energy, into electrical power.

What is the purpose of step-up transformers in the power grid?

Step-up transformers are used to increase the voltage of electrical power after it is generated. This is done to reduce the current, which helps minimize power losses and allows for the use of thinner conductors during long-distance transmission.

How do transformers work on the principle of electromagnetic induction?

Transformers work on the principle of electromagnetic induction, which states that a conductor with current flowing through it creates a magnetic field. When this magnetic field changes, it induces voltage in a nearby secondary coil, allowing current to be transferred without direct contact between the coils.

Why are high voltage levels used in power transmission?

High voltage levels are used in power transmission to reduce the current, which in turn reduces power losses due to the heating effect in conductors. This allows for the use of smaller, more cost-effective conductors and minimizes energy loss over long distances.

What role do substations play in the power grid?

Substations play a critical role in regulating voltage levels, protecting the grid, and managing the flow of electrical power. They house equipment like transformers, circuit breakers, and surge arresters to ensure the safe and reliable operation of the power grid.

Why is air used as an insulator for transmission lines?

Air is used as an insulator for transmission lines because it provides sufficient insulation to prevent electrical arcing between the conductors and the ground. The high placement of transmission lines ensures a large air gap, enhancing the insulation effect and preventing short circuits.

What are the differences between step-up and step-down transformers?

Step-up transformers increase the voltage and reduce the current, which is ideal for long-distance transmission. Step-down transformers, on the other hand, decrease the voltage and increase the current, making it suitable for safe delivery of electricity to consumers at usable voltage levels.

Why are transformers so crucial to daily life and power distribution?

Transformers are crucial because they manage voltage levels throughout the power grid, ensuring efficient transmission and safe distribution of electricity. Without them, it would be impossible to deliver electrical power efficiently over long distances or safely to end consumers.

What would happen if we tried to deliver power directly from a power station to consumers without using transformers?

If power were delivered directly from a power station to consumers without using transformers, the high current required would cause significant energy loss due to heating, potentially melting conductors. This would make it impractical and unsafe to distribute electricity efficiently.

Outlines

00:00

📊 Introduction to Power Grids

In this opening paragraph, the instructor introduces the topic of the video: how power grids work. The discussion outlines the main components of the power grid, including generation, transmission, and distribution. By the end of the video, viewers will understand how power is transmitted from power stations to consumers and will be able to recognize components like transformers, substations, and transmission towers.

05:01

🌍 Problem of Power Losses and Solutions

This section delves into the challenge of transmitting electricity over long distances, which leads to power losses due to the resistance of electrical conductors. The concept of power loss (I²R) and the importance of reducing current by increasing voltage to minimize these losses are explained. The paragraph also highlights why large conductors are impractical and how high voltage transmission helps to reduce losses and save costs.

10:05

⚡️ Role of Transformers in Power Grids

This paragraph explains the critical role of transformers in managing voltage levels in the grid. It describes how transformers use electromagnetic induction to transfer current between coils without direct contact. The process allows for voltage adjustment, with step-up transformers increasing voltage for transmission and step-down transformers reducing voltage for distribution. Transformers are crucial for efficient power transmission over long distances.

15:06

🏢 Substations and Distribution

In this final section, the focus shifts to how electricity reaches consumers after high-voltage transmission. Substations are introduced as key components that help control and protect the grid. They house transformers and other equipment, such as surge arresters and circuit breakers. The paragraph concludes by discussing how electricity is stepped down to safe levels for different consumers, from industrial plants to households, ensuring that power is delivered efficiently and safely.

Keywords

💡Power Grid

A power grid refers to the network that delivers electricity from power plants to consumers. It consists of generation, transmission, and distribution systems, each playing a role in efficiently transferring electricity. The video explains how the power grid is divided into these sections, ensuring energy reaches homes from distant power stations.

💡Generation

Generation is the process of converting energy from different sources (like coal, water, or wind) into electrical power. The video highlights that while we say 'generation,' it's more accurate to say 'conversion,' as per the law of conservation of energy. Examples include coal-fired stations, wind turbines, and hydroelectric power plants.

💡Transmission

Transmission refers to the stage in the power grid where electricity is sent over long distances, often at very high voltages, to reduce energy loss. The video explains how increasing voltage and reducing current helps minimize losses in transmission, allowing for the use of thinner conductors to save costs.

💡Distribution

Distribution is the final stage in the power grid where electricity is stepped down to lower voltages suitable for consumers like homes or businesses. The video describes how transformers at this stage reduce voltage levels to safe values, such as 220V for homes, after being transmitted over long distances at high voltage.

💡Transformer

A transformer is a device used in power grids to change the voltage of electricity—either stepping it up for transmission or stepping it down for distribution. The video emphasizes their importance, explaining how they work through electromagnetic induction, helping reduce energy losses and making electricity delivery more efficient.

💡Electromagnetic Induction

Electromagnetic induction is the process where a changing magnetic field creates electrical current in a conductor. In the video, this concept is key to understanding how transformers operate, as it allows for the transfer of electricity between coils without direct contact, enabling voltage changes in the grid.

💡Voltage

Voltage refers to the electrical potential difference, or the force that pushes electric current through a conductor. The video explains the critical role of increasing voltage to reduce current during transmission, minimizing energy losses and enabling more efficient long-distance power delivery.

💡Current

Current is the flow of electric charge, measured in amperes (amps). The video discusses how higher current leads to greater heat and energy loss in power lines, which is why the grid operates by increasing voltage and reducing current to optimize energy transmission over long distances.

💡Resistance

Resistance refers to the opposition to the flow of electric current, causing energy loss as heat. The video explains how reducing current can minimize the heat generated by resistance in conductors, which is a key reason why transformers step up voltage for efficient power transmission.

💡Substation

A substation is a facility where voltage levels are adjusted and parts of the grid are isolated or protected. The video explains their role in both transmission and distribution stages, using components like transformers and circuit breakers to maintain the grid's stability and safety.

Highlights

The video explains the fundamental components of a power grid, including generation, transmission, and distribution, as well as their roles in delivering electricity from power stations to homes.

The video clarifies the misconception that power generation means creating energy, instead emphasizing the conversion of energy from one form to another in accordance with the first law of thermodynamics.

Various energy sources like coal, hydro, and wind are converted into electrical power using turbines and generators, illustrating the versatility of power generation methods.

The video introduces the challenge of power loss over long distances due to conductor resistance and explains the necessity of using transformers to increase voltage and reduce current.

Transformers play a crucial role in the grid by stepping up the voltage after power generation to minimize transmission losses, making the power grid more efficient and cost-effective.

The concept of electromagnetic induction is explained as the principle behind transformers, which allows voltage to be transferred between coils without direct contact.

The video highlights the importance of alternating current (AC) for transformers to function effectively, as the changing magnetic field is necessary for voltage induction.

Step-up transformers increase voltage for transmission, while step-down transformers reduce voltage to safe levels for end consumers, demonstrating the adaptability of transformers in different stages of the power grid.

Transmission lines, held by tall transmission towers, are air-insulated to prevent electrical arcing to the ground, ensuring safe and efficient power transfer over long distances.

Substations serve as critical nodes in the grid, containing equipment like surge arresters and circuit breakers to protect and isolate parts of the grid during faults or surges.

The distribution stage adjusts voltage levels based on the needs of various consumers, from industrial plants to residential homes, showcasing the grid's ability to cater to diverse electricity requirements.

The video underscores the ubiquity of transformers in urban areas, as they are essential for delivering low-voltage power to consumers safely and efficiently.

The importance of reducing current in transmission lines is explained, as lower current reduces power loss due to heat generation, thus enhancing the overall efficiency of the grid.

The video explains that air insulation is a practical solution for transmission lines to prevent short circuits and ground faults without the need for expensive physical insulators.

Power grids are designed with multiple safety measures like substations and insulators to ensure continuous and reliable electricity supply, even during unexpected events like lightning strikes or equipment failures.

Transcripts

- [Instructor] Hi, John here.

In this video, we're going to have a look

at how power grids work.

We'll look at all of the main components

that make up a power grid,

and I'll explain to you how they work together

in order that we can get electricity

from a power station to your home.

By the end of the video, you'll know how power grids work,

what all the main components are,

what their purpose and function is within the grid,

and if you're ever out and about in the real world,

you'll be able to walk passed things

like electrical transformers, or substations,

or transmission towers,

and you'll be able to identify them visually

and know why they're there and what their purpose is.

So let's start by looking

at a basic diagram of a power grid.

You can see here on our power grid

that we've got five letters,

and these five letters are A, B, C, D, E,

and they indicate different parts of our power grid.

If we look at letter A,

it marks the generation part of the power grid.

If we look at letter B,

this represents the transmission part of the power grid.

Letter C is the distribution part,

and letters D and E represent our end consumers.

Generally, when we're talking about power grids,

we split it into three main sections,

generation, transmission, and distribution.

If you wanna talk about letters D and E,

then we'll simply refer to them as the consumers.

I suppose you could call it

the consumption part of the power grid.

You can see on the diagram

that we've actually got some transformers

and substations between the letters,

we've got a power transformer,

transmission substation and distribution substation.

Don't worry about those too much now.

I'm gonna explain to you what transformers are used for

and why we have substations, et cetera

a little bit later in the video.

So let's go to letter A first, generation.

Now don't be fooled by the name.

We refer to it as power generation

in the power generation industry,

but we're not actually generating any power.

The power that we're referring to is electrical power,

and it's not possible to create or destroy energy,

and therefore it's not possible

to create or destroy electrical power either.

If you wanna get technical,

this is actually called the first law of thermodynamics,

also known as the law of conservation of energy,

and it simply means that we can transfer energy

from one form to another,

but we cannot create or destroy it.

So in order to get the energy

that we're gonna put into our power grid,

we're going to need to find another energy source

and then convert that energy source into electrical power.

Now there are various ways of doing this.

If we're burning coal, then we burn coal within a furnace,

we release the chemical energy that the fuel contains,

we turn it into heat, we transfer that heat to water,

the water gets heated up and turns to steam,

we put the steam through a steam turbine,

the turbine rotates,

and we transfer the mechanical motion,

that is the mechanical energy,

can also say mechanical power,

to a generator.

Now this generator is actually what they refer to

as a synchronous three phase generator,

at least 95% of the times in the power industry

that's what it will be,

and the generator converts the mechanical power

that it's getting from the steam turbine

into electrical power.

So we started with chemical energy

that's contained within a fuel,

and we burned it and we turned it into, in the end,

electrical power.

If we're looking at a hydroelectric power station,

we'll take the pressure energy, or potential energy,

we'll take the kinetic energy,

and we'll harness this

by letting it flow across a hydro turbine runner,

the runner rotates,

and then we pass this mechanical motion

or mechanical power onto our generator,

and the generator turns that mechanical power

into electrical power.

So there are a number of different ways

in order that we can harness different energy sources

in order to get our electrical power.

Those are just two common ones.

A wind turbine is much the same.

We're just taking rotary motion

and using that to rotate a rotor in a generator.

So now that we've generated our electrical power,

I say generated,

but I suppose we really should say converted.

Either way, we've got our generated electrical power,

and now we're gonna need to feed it into the grid

so that we can send it to our consumers.

Now it's at this point that we encounter our first problem.

Most power stations are very far away from end consumers.

If we were to lay a cable or a electrical conductor

from our power station to our end consumers,

and let's just imagine for a moment

that our end consumer is 20 kilometers away,

well we're going to encounter losses

due to the resistance of our electrical conductor

and also due to the heat that's generated

as electricity or electrical current, that is amps,

flows through our conductor.

This wouldn't be such a big problem

if we could have a very large conductor,

but unfortunately, having a very large conductor

that stretches across 20 kilometers of land

is not very practical.

So we need to go back and have a look at why

we've got such large losses

whenever we dispatch power over a distance.

Well the equation for electrical power

is voltage times current,

and the equation for power loss is I squared R.

The I indicates current, and the R indicates resistance.

We can vary the resistance in our cables

by having good electrical conductors,

and these include materials like copper and aluminum

which have high conductivity.

But these materials cost a lot of money,

and considering we're potentially going to need

thousands of kilometers or thousands of miles of conductor,

we want to make these conductors as thin as possible,

so they need to have quite a small diameter.

The problem here is,

as we reduce the diameter of a conductor,

its ability to carry current reduces also.

When current flows, it generates heat.

If we have a very thin conductor and a very high current,

the current will simply melt the conductor.

So how do we reduce the current?

Well we can reduce the current by increasing the voltage.

Power equals voltage times current,

or P equals V multiplied by I.

So if we increase V by a factor of 10,

then I has to reduce by a factor of 10.

That has to occur

because if we want to balance both sides of the equation,

the power out has to remain always the same.

That means if we increase the voltage,

we have to proportionately decrease the current.

So we need to increase the voltage, that much we know.

And if we can do that, we'll reduce the amount of heat

that's generated as current flows through our conductor.

That means we can have thinner

or smaller diameter conductors,

which is ultimately gonna save us some money.

But the other large benefit here

is that power losses are represented

by P equals current squared, multiplied by R.

So power loss equals current squared,

multiplied by resistance.

So the big number here is current.

On this example here,

you can see that if we double the current

and make no other changes to the equation,

we quadruple our power losses.

That doesn't happen if we double our resistance value.

So our priority, if we wanna reduce power losses,

is to reduce the value of current,

and we can do this by increasing the voltage.

So to recap, in order to have smaller conductors,

which ultimately saves us money

because they can be much thinner

or have smaller diameters than larger conductors,

and in order to reduce our power losses

mostly due to the generation of heat,

we need to reduce our current level as much as possible.

How are we going to do that?

This is why we have electrical transformers.

People underestimate just how important

electrical transformers are to our daily lives.

You may think that they're not that important,

and perhaps you may think

you haven't seen many of them around before,

but if you live in a city or town,

I can guarantee that there'll be a transformer

within about 400 meters radius

of where you're sitting right now.

You might not notice them

because sometimes they're hidden inside houses,

or small buildings,

or sometimes they've just got a wall around them

so no one can see them,

but they are a hundred percent there.

They're essential to the way we live our daily lives.

Let's now discover exactly why.

We need to increase the voltage.

We know that much because we need to reduce the current.

Transformers work on the principle

of electromagnetic induction,

and this states that every conductor

that has current flowing through it

creates a magnetic field.

If we take a conductor

and we wrap it into the shape of a coil,

and then we take another conductor and place it nearby,

we can actually transfer current

from one conductor to the other

without them ever physically

coming into contact with each other.

Electricity and magnetism are linked.

That means if one of the conductors

is connected to a power source

and electrical current is flowing,

the magnetic field that surrounds that coil

is going to have an impact on the other coil nearby.

What's really interesting though

is this only works with alternating current.

The magnetic field has to be constantly changing

in order that we can induce voltage in our other coil.

The coil that's connected to the main power supply

is referred to as our primary coil.

The alternating current that is flowing through that coil

creates a magnetic field that expands and contracts

as the current flows back and forth through the coil.

This induces voltage in our secondary coil.

In this way, we can transfer current

from our primary coil to our secondary coil

without them ever coming into contact with each other.

As current flows back and forth on our primary coil,

the magnetic field increases and decreases,

and that causes current to flow back and forth

in our secondary coil.

In electrical transformers, we actually mount these coils

onto a big block of steel.

The big block is called the transformer core,

and although it looks like a solid piece of metal,

it's actually made up of a lot of thin, laminate sheets

which are either glued or clamped together.

The reason we have the core

is just to focus the magnetic field

from the primary winding to the secondary winding.

The core makes the transformer a lot more efficient.

What's really fascinating is if we add more windings

to the secondary side of our transformer,

we can increase the voltage.

If we reduce the number of secondary windings

on our transformer,

we reduce the voltage.

Remember, we want to increase the voltage

in order that we can reduce the current

and reduce our power losses.

So transformers that are installed

directly after power stations

have many, many more secondary windings

than primary windings.

This allows us to increase the voltage.

Transformers that increase voltage

are referred to as step-up transformers,

and transformers that reduce voltage

are referred to as step-down transformers.

The transformer directly after a power station

is called a generator step-up transformer, or GSU for short.

Once we have increased the voltage,

we're gonna send our electrical power to a substation.

This is usually some type of open air switch yard.

And then we're gonna feed that power

into our transmission lines.

And these lines are held by our transmission towers.

Transmission towers have a very unique shape.

They're often very tall,

and there's a good reason for this.

The electrical conductors that are used

on our transmission lines are not insulated.

In your home, when you have an electrical conductor

like a copper cable for example,

you're going to have a sheet of plastic or rubber

around that cable,

and that is what insulates the cable

and stops the electrical current

from shorting out by going to ground.

So insulate the conductor in our homes

in order that current flows where we want it to

and that we don't have short circuits.

The conductors that we use on our transmission lines

do not have any plastic or rubber surrounding them,

but they are, however, insulated.

You just can't see the insulation.

They're what we refer to as air insulated.

And the reason we have to hang these conductors

on a large tower

is because air is not such a fantastic insulator

that we can leave the conductors

hanging around one meter above the ground.

If we did this, the air surrounding the conductor

would be ionized to such a degree

that we would get an electrical arc

from the conductor to ground.

This arc would look like a large spark.

So we hang our conductors high above the ground

so that there is a large air gap

between the conductors and ground.

This gives us a large amount of air insulation.

Not only that, but it keeps the transmission lines

well out of the way of the general public

because we don't want people

driving into our transmission lines

or accidentally flying a kite into them

and causing a ground fault.

It's not good for the power grid,

and it's definitely not good

for the person holding the kite.

Although we've insulated our transmission lines

from the ground,

we also need to insulate them from the tower itself,

which would act as a very efficient conductor

if our transmission lines came near

or touched onto the tower itself.

To ensure this doesn't happen,

we hang our transmission lines from the tower

using insulators.

Insulators allow us

to bring the transmission lines to the tower

without bringing them too close to the tower.

Initially, when we generated electrical power

using our generator,

we may have had a voltage of 20,000 volts.

When we reach the transmission stage,

we may have a voltage of 130, 230, 340, 500,

or even 765,000 volts.

That is a lot of volts,

especially when you consider in your home

you may use 220 volts or 110 volts.

So we've massively increased the voltage

in order to reduce our transmission losses

and in order to be able to reduce

the size of our conductors.

We're now distributing our power

across potentially hundreds of kilometers or miles

before we reach the next part of the power grid.

Once again, we reach a substation.

Substations contain all of the equipment we need

in order to reduce and increase voltage.

Not only that, but they allow us to separate

various parts of the grid from each other.

This means we can protect

different parts of the grid from each other

so that if we have things like lightening strikes

or power surges,

we can isolate certain areas of the grid

rather than have a complete blackout.

Substations are critical if we want to ensure

that the machinery and the components

that make up the power grid

are as protected as much as possible

so that we can increase the reliability of the grid.

Substations contain items such as surge arresters

or lightening arresters,

circuit breakers, switchgear,

disconnectors, and transformers.

We've left the transmission stage,

and now we're gonna go to the distribution stage.

We don't want to send electrical power to our end consumers

at 765,000 volts.

They're not gonna like that very much at all.

So we'll reduce the voltage using a step-down transformer.

And remember, this is a transformer

that has far fewer windings on the secondary side

than it does on the primary side.

Different consumers require different voltages.

Industrial plants, for example,

may require voltage to be delivered

at 30,000, 20,000, or 10,000 volts

depending upon the application of the plant.

Large office buildings and hospitals

will require lower voltages.

And by the time we reach the general consumer

living at home,

they're gonna require voltages of 380 volts to 40 volts,

or even 110 or 120 volts.

Because there are multiple consumers

requiring multiple voltage levels,

we're going to need multiple transformers,

and each specific transformer

is going to cater for one specific voltage level.

Now that we've reduced the voltage to quite low levels,

it's essential that we deliver that electrical power

over as short a distance as possible.

And this is the reason why,

if you're living in a city or town,

a transformer will be located nearby.

So you now know how we get electrical power

from our power generation source,

which may be a coal-fired power station,

perhaps a series of wind turbines

or a hydroelectric power plant, et cetera,

and how we transfer that electrical power to our homes

even though our homes may be miles and miles

or kilometers and kilometers away from the power source.

If you wanna learn more about engineering,

then be sure to check out our website.

We've got over 25 hours of engineering video tutorials,

and we cover everything from diesel engines

to valves to pumps to power stations.

If you think that sounds interesting,

then check out the links in the video description area.

If you enjoyed this video,

then please do like it or share it on social media.

It really does help us out.

And don't forget you can subscribe to the YouTube channel.

Thanks very much for your time.