Transcript Slide 1

P1.4.2 The National
Grid
Mr D Powell
Connection
•
•
•
Connect your learning to the
content of the lesson
Share the process by which the
learning will actually take place
Explore the outcomes of the
learning, emphasising why this will
be beneficial for the learner
Demonstration
• Use formative feedback – Assessment for
Learning
• Vary the groupings within the classroom
for the purpose of learning – individual;
pair; group/team; friendship; teacher
selected; single sex; mixed sex
• Offer different ways for the students to
demonstrate their understanding
• Allow the students to “show off” their
learning
Activation
Consolidation
• Construct problem-solving
challenges for the students
• Use a multi-sensory approach – VAK
• Promote a language of learning to
enable the students to talk about
their progress or obstacles to it
• Learning as an active process, so the
students aren’t passive receptors
• Structure active reflection on the lesson
content and the process of learning
• Seek transfer between “subjects”
• Review the learning from this lesson and
preview the learning for the next
• Promote ways in which the students will
remember
• A “news broadcast” approach to learning
Mr Powell 2012
Index
P1.4.2 The National Grid
a) Electricity is distributed from power
stations to consumers along the National
Grid.
b) For a given power increasing the voltage
reduces the current required and this
reduces the energy losses in the cables.
c) The uses of step-up and step-down
transformers in the National Grid.
Mr Powell 2012
Index
What is the National Grid

The “grid” is a system of
cables which link Power
Stations to homes,
businesses, industry and
other infrastructure.

Along the way it has to
modify the electrical current
to make sure that as much of
the energy is delivered as
possible.

Transformers do the
modifications!

This diagram shows the main
routes.
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Index
What is the National Grid

This image shows how the
grid is split in terms of
companies.

However, they are still all
linked together and sell
electricity to each other to
meet the demands.

This is a fake internal
market to allow the system
to be privatised and build a
profit driven service
instead of a nationalised
service.
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Index
Who produces the power.

The power comes from a variety of
sources.

The map shows all the nuclear power
stations

The house here is putting energy back
into the grid from its solar panels.
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Index
Stepping up / Stepping Down
132kV
25kV
230V
Power station
Step up
transformer
Step down
transformer
Homes

If we keep the voltage the same all the way and wanted the process to be
90% efficient. Throughout the grid we would have to use cables that were
13cm in diameter! They would weight 7000 tonnes . They

If we step up the voltage to 132kV the cables would be 4mm in diameter
but we would still only lose 10% of the energy in heat.

Also home electricity would be dangerous at such high voltages so it must
stepped down anyway.
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Index
Revision...
Copy the diagram and complete the questions in your books on the National Grid
Power station
Step up
transformer
Step down
transformer
Homes
We use the national grid to _ _transfer
_ _ _ _ energy to our homes. The step-up
transformers increase the _ _ voltage
_ _ _ _ _ _ and reduce the _ current
_ _ _ _ _. The
high voltage electricity now at _132
_ _ kV moves with _low
_ _ thermal losses
and means that the wires can be quite _ thin
_ _ _. Finally the step-down
transformers mean that the _voltage
_ _ _ _ is reduced to _230
_ _ V and is useable
in every day appliances. This can only be done with _alternating
_ _ _ _ _current.
_____
from a power station.
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Index
An Argument....
Should power cables be underground or overhead? Here are some of
the arguments used:
1.
2.
3.
4.
5.
6.
They take up valuable land.
They are more difficult to repair.
They are more difficult to install across roads, railways and canals.
They are much more expensive.
They spoil the landscape.
They produce electric and magnetic fields that might affect
people.
Which of the above arguments would you use to argue against:


Underground power cables?
Overhead power cables?
TASK
Imagine you are a spokesperson for an environmental group or power
company going on live radio. Write down an argument using your
own and these ideas from a perspective....
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National Grid....
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Why do we transform the current and voltage?
If we look at this real
situation where we are
transferring energy
down the system.
Look at your cases A-E
and compare using the
table on the sheet.
Case
Power Transmit /kW
A
400
Voltage /kV
Current /A
4
Power Loss / kW
Power
received /kW
1.6
B
C
8
393.6
D
E
1
0
Mr Powell 2012
Index
Transformers

These are really basic devices we can
change the voltage and current at
which the energy is transferred.

The idea of this is to save power.

The simple circuit consists of a Power
supply, two bulbs and a transformer.

The current to the lower bulb is
transferred indirectly by a magnetic
field induced in the iron loop.

The current has been transformed
and p.d. has increased and current
reduced
http://www.practicalphysics.org/go/Experiment_349.html
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Index
Transformers – Results....
The results show an ideal situation where
0.02W are lost due to heating effects
1:3
V, Voltage
(V)
I, Current
(A)
P, Power,
W
10 Turns
(Np)
1.98
0.25
0.5
20 Turns
(Ns)
3.96
0.12
0.48
P = VI
http://en.wikipedia.org/wiki/Transformer
http://www.practicalphysics.org/go/Experiment_349.html
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Index
Transformers & everyday uses...

Here is an example of how we can
transform voltages and currents.

The core is the same as in the previous
slide but now you can see that the
number of turns of wire are different.

The ratio of turns either steps up or
steps down the voltage.

What happens is when the current
flow (alternating current) flows back
and fourth in one set of wires it creates
(induces) a current in the other set of
wires.
This example is a travel adapter plug!

Mr Powell 2012
Index
P1 4.3 National Grid “Quick Test”....
Basic Demand
Student Assessed!
1.
Connect up these constituent parks in a flow chart to
show the “National Grid” in the right order
overhead power lines (132kV), step-up transformer,
underground cables, homes (230V), step-down
transformer, power station 25kV
(3 marks)
Med Demand
2. Give two examples of equipment where we use a
transformer in the home and explain why for one of
them? (3 marks)
High Demand
? / 10
4. Explain one disadvantage and advantage of using
underground power cables? (2 mark)
5. Why do we step up the voltage so high and then so low
for home use? (2 marks)
Mr Powell 2012
Index
P1.4.2 The National Grid
P1.4.2 The National Grid
P1.4.2 The National Grid
a) Electricity is distributed from
power stations to consumers along
the National Grid.
a) Electricity is distributed from
power stations to consumers along
the National Grid.
a) Electricity is distributed from
power stations to consumers along
the National Grid.
b) For a given power increasing the
voltage reduces the current
required and this reduces the
energy losses in the cables.
b) For a given power increasing the
voltage reduces the current
required and this reduces the
energy losses in the cables.
b) For a given power increasing the
voltage reduces the current
required and this reduces the
energy losses in the cables.
c) The uses of step-up and stepdown transformers in the National
Grid.
c) The uses of step-up and stepdown transformers in the National
Grid.
c) The uses of step-up and stepdown transformers in the National
Grid.
P1.4.2 The National Grid
P1.4.2 The National Grid
P1.4.2 The National Grid
a) Electricity is distributed from
power stations to consumers along
the National Grid.
a) Electricity is distributed from
power stations to consumers along
the National Grid.
a) Electricity is distributed from
power stations to consumers along
the National Grid.
b) For a given power increasing the
voltage reduces the current
required and this reduces the
energy losses in the cables.
b) For a given power increasing the
voltage reduces the current
required and this reduces the
energy losses in the cables.
b) For a given power increasing the
voltage reduces the current
required and this reduces the
energy losses in the cables.
c) The uses of step-up and stepdown transformers in the National
Grid.
c) The uses of step-up and stepdown transformers in the National
Grid.
c) The uses of step-up and stepdown transformers in the National
Grid.
P1.4.2 The National Grid
P1.4.2 The National Grid
P1.4.2 The National Grid
P1.4.2 The National Grid
We use the national grid to _ _ _ _ _ _ energy to
our homes.
We use the national grid to _ _ _ _ _ _ energy to
our homes.
The step-up transformers increase the _ _ _ _ _ _ _
_ and reduce the _ _ _ _ _ _.
The step-up transformers increase the _ _ _ _ _ _ _
_ and reduce the _ _ _ _ _ _.
The high voltage electricity now at _ _ _ kV moves
with _ _ _ thermal losses and means that the wires
can be quite _ _ _ _.
The high voltage electricity now at _ _ _ kV moves
with _ _ _ thermal losses and means that the wires
can be quite _ _ _ _.
Finally the step-down transformers mean that the
_ _ _ _ _ is reduced to _ _ _ V and is useable in
every day appliances.
Finally the step-down transformers mean that the
_ _ _ _ _ is reduced to _ _ _ V and is useable in
every day appliances.
This can only be done with _ _ _ _ _ _ _ _ _ _ _
from a power station.
This can only be done with _ _ _ _ _ _ _ _ _ _ _
from a power station.
Case
Power
Transmit
/kW
Voltage
/kV
Current
/A
Power
Loss /
kW
Power
received
/kW
A
B
C
C
D
E
D
What do you think?
A
E
B
P1.4.2 The National Grid - Worksheet
Case
Power Transmit /kW
Voltage /kV
Current /A
Power Loss / kW
Power received
/kW
A
400
100
4
1.6
398.4
B
400
75
5.3
2.8
397.2
C
400
50
8
6.4
393.6
D
400
24
16.6
27.5
372.5
E
400
1
400
400
0