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.
