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The Power Grid

TCIP Educational Development

TCIPG: Trustworthy Cyber Infrastructure for the
Power Grid

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Lesson 1

The Power Grid

Use the applet at http://tcipg.mste.illinois.edu/applet/pg

to explore how power is distributed from generators to
the communities. In the applet there are five different
types of generators delivering electricity to three
communities.
1. When the applet opens, are the generators making more
or less power than the communities are using? ____
Some of the generators are able to vary their production.
Click on the up and down arrows to the right of MW output

Courtesy of DOE/NREL, Credit - Warren Gretz

labels to change the

Read about
the power
grid here.

The power grid refers

to the system of
producers and consumers
of electricity. It

includes power generators, the users

of electricity, switches that control
the electricity, and the system of

2. Find the five generators available in the applet. List the

types and their outputs here. If a generator is able to vary its
output, give its range.
a.
b.
c.
d.

substations, power lines, and

e.

transformers that deliver the

The arrows show the direction of the power flow and indicate the

electricity.
A community might have a generator
to provide its power. The generator
may be able to vary its production as
the usage of the customers changes,

amount. Open or close the blue switches by clicking with the mouse.
Explore the system by changing the power outputs and opening or
closing the switches.

When the applet opens (or is reset), power is being produced by

four of the five generators.

but there may be times when the

3. Find the total amount of power being produced. ________

demand for energy is too great for

You can see the power moving from the generators through the

the generator. Then the community

substations and to the users in Commerceton, Industryville, and

buys electricity from another

Residenceburg.

source. At other times the

generator may be making more
electricity than the community is
using, so it
One estimate of home
energy use states 3.3 MW wants to
are needed for 1000 homes
sell it.

4. Find the total amount of power being used by these

communities. _________
Any power that is not used by the communities in the system is
sent to other users in other systems.
5. How much power is being sent to external systems?
_________________

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The Power Grid

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Lesson 2

When the applet at http://tcipg.mste.illinois.edu/applet/pg opens (or is reset), power is being produced by four of the five generators.
1. Close the switch to put the nuclear plant online. What changes?

Watch the arrows and

the numbers alongside
the transmission lines
to see changes in the
system.

2. How much power is being sent to external systems? ________________

3. What happens if the switch to one of the external systems is opened?

4. How can you match the power generated to the power used?

A power substation

You see some

5. Reset the system and take all of the generators

parts of the

offline. What happens?

power grid all

around you.
There is
probably a
power pole with a transformer drum very

6. Put only the hydroelectric plant back online. Now

what happens?

near where you live. If your neighborhood

has underground power, the transformer
is in a green box that is about one meter
on each side. There is a power substation
like the one in the photo nearby too.
Substations can split the power
distribution into two or more directions,
but they do not make or use power. So

Reset the system, then answer these questions.

7. Adjust the coal power plant to be on line at maximum
power. How much electricity is flowing into substation 3?
___________________
8. How much electricity is flowing out of substation 3?
____________ Where is it going?

the power entering a substation is equal to

the power leaving the substation. Another
job of the substation is to take the high
voltage power produced by the generators
and transform it to a lower voltage that

9. What changes when you open the switch on the line

leaving the coal plant?

can be used in homes, schools and

businesses.

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The Power Grid

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Lesson 3

When the applet at http://tcipg.mste.illinois.edu/applet/pg opens

Victoria Towers residents sit outside with their
flashlights during the power blackout Aug. 14, 2003,
in Meriden, Connecticut (Photo AP)

(or is reset), all of the power flow arrows are green. The
transmission lines have varying capacities. Just

as in an actual power system, if a line is asked to carry too much power the line
will be opened creating a power outage. To make it easy for the system
operator (thats you!) to see when lines are in danger of becoming overloaded,
the arrows in the applet change color.
1.

Reset the system and notice the line leading from Substation 5 to
Commerceton. How much power is this line carrying? _________ Click on
the up arrow to increase Commercetons power demand. What happens to
the arrows on the line?

2. At what load do the arrows change to orange? _______________ What

color are the arrows when the demand is 1000 MW? ___________________ What happens
when the load on the line is increased again?
How can you fix it?

Explore the applet to find the line maximum capacities for all the lines.
Power leaving the generating

Reset the system, put the nuclear power plant online and then

plant is carried by high

increase the power demanded by Residenceburg to 1850 MW.

voltage, long distance

3. Whats causing a problem?

transmission lines to a
distribution substation. These lines
look like the photo. The power leaves
the substation on the lines you see

4. Reduce the potentially dangerous line overload without

taking the nuclear plant offline. How do you do this?

strung from power poles. The

transmission lines that have the largest
diameters are designed to carry the

5. Its a hot summer day and power demand in Residenceburg

most power. Transmission lines become

is 1600 MW. Commerceton is demanding 850 MW and

hot and expand if they carry more

Industryville needs 800 MW. You put all of your

power than they are designed to carry.

generators online at maximum capacity. Are all of your

This can cause the line to sag and touch

lines operating safely?

the ground or some other object.

When this happens the line is opened
and a power outage will occur.

6. Are you able to produce enough power to meet the demand

or do you need to get power from the external system?

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The Power Grid

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Lesson 4

When the applet at http://tcipg.mste.illinois.edu/applet/pg opens (or is reset), the generators are
producing more power than the communities are using, and power is being sent to the external
system. Power system operators try to match power generation to demand, because this is usually
least expensive. When communities need more power, the generators are adjusted. The
transmission line flows need to be kept at safe levels too.
Reset the system and then set the power demand for
Residenceburg at 1500 MW, for Industryville at 600 MW
and for Commerceton at 800 MW. Turn the nuclear
power plant on to meet this increased demand.
1.

Bad weather can sometimes cause breaks in

transmission lines. What happens to the system when
you open the line between substations 4 and 6?

Courtesy of DOE/NREL, Credit - Kelly, Marguerite

Reset the system, turn on the nuclear power plant and then open the line between substations 1
and 2.
2. What happens?

3. What is the problem?

4. Fix it by changing one switch. What did you do?

There are six major Regional Transmission

Organizations (RTOs) or Independent
System Operators (ISOs) in the United

5. Reset the system and then set both the coal

generator and Industryville to 600 MW. What is
happening between substations 2 and 3?

States. These voluntary, independent

organizations monitor electricity generation
and demand and communicate with power

6. Open the line between substations 2 and 3. Now

what is happening?

plants and utilities to balance supply and

demand. The Federal Energy Regulatory
Commission (FERC) encourages the
formation of these nonprofit organizations
because they promote efficiency in
wholesale electricity markets.

7. What happens to the other communities?

8. Which line in this system do you think is most

likely to overload?

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