SUBJECT 1: Hey, Tino.
What are you doing?
SUBJECT 2: Testing out this new light bulb
demo I just built to show how efficient LED light bulbs are
compared to the old style ones.
SUBJECT 1: That's cool.
Can I try it?
SUBJECT 2: Yeah, here you go.
All right, crank away.
So you're going to start cranking on a three watt
LED light bulb--
pretty easy, right?
SUBJECT 1: Yeah, that's real easy.
SUBJECT 2: Now I'm going to kick on 25 watts of the older style.
SUBJECT 1: Er!
Jeez!
SUBJECT 2: Pretty hard, right?
SUBJECT 1: That is tough.
SUBJECT 2: Yep.
That's 10 times the power almost.
SUBJECT 1: Man, imagine how many people
would take the power the United States at 500,000
megawatts of peak demand.
Good thing we have power generation stations
to take care of that.
SUBJECT 2: I heard that.
ERIK HURD: How do we generate the electricity that is
used all over the world today?
There are many different forms of power generation being used,
including the burning of fossil fuels, nuclear power,
and renewables.
Today, the majority of our electricity
is created by burning of fossil fuels, primarily coal
and natural gas, to spin turbines
that are connected to an electromagnetic generator.
This is changing as renewables and natural gas
are becoming more cost effective.
Utilities produced as energy inside of large power plants
also known as generation stations.
Let's start with the question, what is a generator
and how does it work?
A generator converts mechanical or kinetic energy
into electrical power or electricity
by electromagnetic induction, which
is simply varying a magnetic field within a coil of wire.
This phenomenon is explained by Faraday's law,
as shown here in this example.
As that induced current travels in a loop on the wire,
it will create a magnetic field.
Because the field is continuously
changing, or alternating, it creates
what we would call a sine wave or
alternating current waveform.
Historically the first generator invented
was a direct current or DC generator called a dynamo.
DC power produced by these generators
was limited because the generation source
had to be close to the loads.
Then came alternating current, produced by AC
generators, called an alternator,
or a synchronous generator.
The major advantage of the AC generation
is that with transformers, the voltage levels
can be changed up and down to transmit
that power far distances to the loads that require it.
So how does a generator work?
The two main parts of a generator
are the rotor and the stator.
The rotor is the part that rotates and consists
of many loops of copper wire or bars called field windings.
Field windings are used to create the magnetic field
induced on the metal core to which the wire is wrapped
around.
The stator is the stationary or static part
of the generator that consists of copper windings called
armature windings.
The power that is produced by the generator
will flow out of these armature windings towards the load.
Let's get a better understanding of the basics
of how the rotor and stator interact to generate power.
First of all, we need to understand
that the rotor spins inside the stator
and one full rotation is equal to a complete cycle of power.
In North America, this would equate to one 60 Hertz cycle.
For a generator to produce power,
an electromagnetic induction must
occur between the field windings in the rotor
and the armature windings in the stator.
A magnetic field must be created in the field
windings on the rotor.
Traditionally, this was done using permanent magnets.
But with larger scale generation being needed,
electromagnetic field coils were able to produce
substantially more power.
This is done by applying a DC current, or excitation current,
to the field windings through a pair of carbon brushes and slip
rings.
Slip rings are attached to the shaft of the rotor
and spin with the rotor while brushes are stationary
and connect to the end of a wire with a spring,
pushing on them against the slip ring,
making an electrical connection.
The field winding is a continuous wire
that is looped around a certain number of poles that
are part of the rotor core, with positive polarity connected
on one end and negative on the other.
North and south poles will be created
depending if the coils are wrapped
clockwise or counterclockwise around the poles.
This essentially is creating an electromagnet with a DC source.
This DC current can come from an external source
or from a small exciter rotor with a rectifier that
is attached at the same shaft as the main rotor
and is called self-excited.
This excitation current is a crucial part
in the voltage regulation of the generator.
The magnetic field strength of the field windings on the rotor
can increase or decrease by changing the amount
of excitation current.
The amount of current and the number of turns in the field
windings determine the strength of the magnetic field.
The control of the excitation system
allows the generator to maintain voltage, control reactive power
flow, and assist in maintaining power system stability.
During load changes or disturbances on the system,
the exciter must respond, sometimes rapidly,
to maintain the proper voltage at the generator
terminals for the load.
The two common types of rotors are cylindrical and salient.
Cylindrical will generally operate
at speeds of 1,200 RPM or more and salient at speeds
below 1,200 RPM.
So we know how the magnetic field
is created on the poles of the spinning rotor.
Now let's see how the field transfers
onto the armature windings, or poles, of the stator
and turns into usable power.
The stator is enclosed inside a metal housing
and consists of two main parts--
the outer part of the stator, called the core,
and the armature windings.
The core is generally made of a low loss magnetic material
and used to support the coils of the armature windings
and is also a return path for the lines of magnetic field.
The magnetic field created on the rotor
induces a current onto the armature windings.
The stator windings tend to be larger, highly insulated,
and more complex than the field windings in the rotor
because they must carry the generated power through them
that is of a much higher voltage.
A three phase stator will consist of three windings
where for each phase, there is one group for each rotor poll.
Each group is interconnected and can be
considered as one large coil.
Each group has an output lead from a generator that is
120 degrees from one another.
The leads are typically y or star connected,
and the neutral is usually connected to ground
or brought out with single phase loads.
As the rotor spins, three separate voltages
are created at the stator terminals.
There are other considerations in the stator's
armature windings to consider, such as how
they're wound, how many coils per group,
as well as span and pitch.
The frequency of a generator is directly related
to the number of poles on the rotor and the speed
of which it spins.
For example, for a four pole rotor to rotate at 60 Hertz,
it would have to spin five times faster than a 20 pole rotor,
putting much more mechanical stress on the generator.
Salient pole machines may have 10 to 20 poles, reducing
the stress on these generators, but again run at a lower RPM.
Power plants may choose a rotor with a certain number of poles
depending on the speed needed for the application.
In other words, if the device that
will be spinning the rotor, known as the prime mover,
has a certain operating speed, the rotor
can be selected based off of that RPM.
Even with large fluctuations in load,
large utility generators don't allow the frequency
to change much because they are large rotating masses
and provide significant inertia to the grid.
This is extremely beneficial to the grid
by stabilizing the voltage, but it
could take up to a minute for these units
to get frequency back to the proper level
if something catastrophic happens
because they are so large.
Some widespread blackouts have been
related to significant frequency changes
in the response of large generators
and groups of generators.
Wind and solar have a much faster frequency response
due to the use of electronics, but they
don't provide as much grid stability provided
by large generators with rotating inertia.
For large systems generators, are paralleled with each other
to provide more capacity to feed loads,
and they must be synchronized with each other.
The objective of synchronization is to match speed and phase
position.
So there is little or no transfer of energy
when paralleling multiple units or connecting
to an existing grid, or bad things could happen.
Synchronizing requires matching voltage magnitudes, frequency,
and phase angle.
On systems with commercial or industrial generators,
synchronizing these generators requires a special transfer
switch with that capability.
AC generators have a lot of moving parts,
but the main power producing component is the prime mover.
The most common prime mover is a steam turbine or turbo machine.
It consists of at least one moving
part called a rotor assembly, which is a shaft
or drum with blades attached and is
used in thermal power plants.
This part makes the rotor spin at the desired speed
by using mechanical gears.
Governors on the prime mover system
are used to control the speed of the prime mover, which
then controls the speed of the rotor inside of the generator.
Most of the generation today is still
being produced by burning of fossil fuels,
with coal being the primary fuel of choice.
But in the United States, natural gas
has recently become the leading fuel over coal.
When fossil fuels are burned, they
create heat that boils water in a boiler,
producing steam, sending it to the condensing turbines,
and then exhaust that steam to a condenser.
The exhausted steam is the white smoke
that you would see coming out of cooling towers at a generation
station, and it is of no danger to the environment.
The steam turbine is a form of heat engine
that extracts the thermal energy from the pressurized steam
and uses it to do mechanical work on a rotating output
shaft.
This ultimately spins the rotor of the generator.
Not all fossil fuels are used to heat water to produce steam.
Natural gas power plants can also
burn natural gas mixed with a stream of air, which
combusts and expands through a gas turbine
to spin as its primary mover.
Nuclear power plants are another type of generation source
that provides a very large amount of power and about 11%
of the world's electricity.
In the United States, it provides around 20%
of the electricity used, which is behind natural gas and coal
and slightly more than renewables.
These plants operate in a similar fashion as fossil fuel
plants by heating water to produce steam,
except they don't burn fuels to create heat.
Nuclear power plants get their heat from a chemical reaction
where in the core of the nuclear reactor,
the fission of uranium atoms releases
energy that heats the water to about 520 degrees Fahrenheit.
Renewables are making a large impact
with power production in the world
and accounting for about a third of the world's generation.
The most significant are wind, solar, and hydro.
Hydropower, or hydroelectricity, is by far the largest
form of renewable energy and produces about 24%
of the world's electricity.
In the United States, there are more than 2,000 hydropower
plants in operation and account for around 7%
of the total energy.
The most well-known hydropower plant in the United States
is the Hoover Dam, and it has a total
of 17 generators, each able to generate
up to 133 megawatts, with a total capacity of 2,074
megawatts.
The power plant with the largest available capacity in the world
is the Three Gorges Dam in China,
which utilizes 32 turbines each with a capacity of 700
megawatts and two additional 50 megawatt turbines.
That's an overall capacity of 22,500 megawatts.
To put that in perspective, that is more than double the amount
being produced by the largest nuclear power
plant in the world, which is almost 7,500 megawatts.
Hydroelectric plants generate electricity
like fossil fuels and nuclear power plants
but spin a turbine using the force
of water instead of steam.
A hydro plant uses the pressure of water created
by either a difference of elevation for dams
or the force of water in rivers.
In either case, the head pressure
can be regulated by control gate so when the water flows down
a control pipeline, caught a pen stock,
the pressure builds up, spinning a turbine at the bottom,
and turns the rotor of an AC generator.
Wind power is the next highest producing renewable
behind hydropower at 6% of the United States total generation.
Wind generation is continuing to rise as more of an effort
goes into the production of renewable energy.
Wind generation relies on the spinning of a wind turbine that
turns the rotor of a generator.
This type of generation can be done for individual homes
all the way up to utility scale applications that are generally
many units connected together as a wind farm.
Typically, utility scale windmills in the United States
produce about 1,500 kilowatts each
and have blades that are about 80 feet long.
Our current wind power capacity in the US
is around 82,000 megawatts, second only to China
and the European Union.
The US Department of Energy, or DOE,
projects the US to have 404,000 megawatts of peak wind power
capacity by 2050.
That will be enough to fulfill one third of the power demand
with all turbines at peak output if future projections
are accurate.
Solar power has been on a steady rise
as it becomes more available and a good economic investment.
There are lots of incentives in place
to promote the growth of solar generation
for your home or business.
Solar generation is a totally different type
of generation compared to all the others mentioned so far.
There is no prime mover or AC generator with solar panels.
Solar panels strictly rely on the solar radiation
from the sun to be absorbed by photovoltaic panels
to produce DC power.
The DC power is then converted into AC
by the use of power electronics inside an inverter.
36% of all new electricity generating capacity additions
this past year are actually from solar power.
Solar power has been holding quite steady since 2013
by being about 30% of all added electric power
capacity in the United States year over year.
Our current solar capacity is 69,000 megawatts,
which is on track to double by 2024, adding over 15,000
megawatts each year.
Here at the Power Systems Experience Center,
we have a small wind turbine and several different solar
installations to illustrate how these alternative energy
solutions are viable and can be connected
to your grid or microgrid.
So what does Eaton have to do with generators or power
generation?
Eaton works closely with electric utilities
and provides large and medium voltage circuit breakers
and switch gear for generation stations
as well as electrical equipment to support
the operation of these power plants, like transformers,
arresters, protection systems, and more.
In addition, our services team supports
upgrades and reconditioning of existing switch gear
and excitation systems, as many of these stations
are relatively old.
As some utilities are moving away
from traditional coal fired sources,
they are converting some generators
to synchronous condensers, utilizing
much of the same hardware from these generation systems.
These large, rotating machines can provide or absorb
reactive power, or VARS, to support
the voltage and reactive power requirements of the power grid.
A synchronous condenser is a DC-excited synchronous motor
whose shaft is not connected to anything but spins freely.
This provides stability and voltage control--
when needed, absorbing VARS when load is lost
or providing VARS like a capacitor when
load is added to the system.
Eaton's engineering services group
has been very instrumental in several of these upgrades,
repurposing the synchronous generators
and converting them to synchronous condenses.
Eaton offers two solutions--
brownfield conversion, converting
existing systems, as well as greenfield,
or new installations.
These are especially important for systems
where wind is a significant power generation
source because of the intermittent nature
of the wind.
In addition to traditional power generation stations,
Eaton is heavily involved in the installation and operation
of renewable resources, including significant equipment
and work with hydro power and solar installations.
Finally, our services team is leading the way in the industry
with microgrid solutions tying it all together.
Our microgrid energy optimizer can take any generation source
or energy storage solution and optimize resiliency and cost
depending on the application.
If you want to learn more about different types of power
generation, how electricity is distributed
after it is generated, and how it can be connected
to your power system, contact us or your local Eaton
representative to schedule a visit to the Power Systems
Experience center today.