UNESCO-NIGERIA TECHNICAL &

VOCATIONAL EDUCATION
REVITALISATION PROJECT-PHASE II

NATIONAL DIPLOMA IN
ELECTRICAL ENGINEERING TECHNOLOGY

ELECTRICAL POWER SYSTEM (I)

COURSE CODE: EEC 122

YEAR I- SEMESTER II

PRACTICAL

Version 1: December 2008

1
 TABLE OF CONTENTS

Week 1: Industrial visit to Steam power station

Week 2: Discussion on the Visit to Steam power station

Week 3: Industrial Visit to Gas plant power Station

Week 4: Discussion on the visit to Gas power Station

Week 5: Solar power plant Model

Week 6: Discussion on Solar power plant Model

Week 7: Solar cells output

Week 8: Discussion on solar cells output

Week 9: Wind Energy Model

Week 10: Discussion on Wind energy model

Week 11: Wind Electrical Energy output

Week 12: Discussion on Wind Electrical Energy output

Week 13: Disassembling and Re-Assembling of protective device

Week 14: Cable Testing and Fault Location

Week 15: Short Transmission Line Model

PRACTICAL WORK Week
1
TITTLE: INDUSTRIAL VISIT TO STEAM POWER STATION

OBJECTIVES:

I. For the students to see how a steam power station plant look like.
II. To have a physical look and identification of the different parts of the generating
station.
III. To know how electricity is being generated in the steam power plant.

REQUIREMENTS:

1. Students must be familiar with the necessary safety rules.

2. Students must wear all the safety wears before entering the plant e.g.; helmet, safety boot
3. Students must be accompanied by the lecturer teaching the electrical power course while
in the school.

PROCEDURES:

 On arrival at the venue (power station) the lecturer will present an acceptance letter of the
visit to the officer in charge of the industrial visit in the generating station
.
 The officer will appoint the person that will lead the team i.e. the students and the lecturer
into the plant. The officer or leader of the team with start by giving the general
description of the generating station, then move from one part of the station to the other.

 Finally, their should be period for questions and answer, where the students will be
asking question associated with the generating station.
Practical Work Week 2

TITTLE: DISCUSSION ON THE INDUSTRIAL VISIT TO STEAM POWER STATION

OBJECTIVES:

I. To determine the level of understanding in the students from the visit.

II. To allow the Students express their feelings and observation with respect to generating
power station (Steam power station).
III. To have an interaction the lecturer concerned to lead them during the visit so as clear
doubtful areas that are clear to the students while in the power station, on which the
could not asked.

REQUIREMENTS:

1. Writing materials such as pencils, biros, etc.

2. Student’s jottings i.e what the students must have jotted down during the visit.
3. Students who visited the steam power station and the lecturer teaching the electrical power
course while in the school and also accompanied during the visit.

PROCEDURES:

 The lecturer should start by given a general introduction of the discussion of the industrial
visit to the steam power station.
.
 A general summary of the industrial visit, mentioning what happened from the first point up
to the last point of the activities that took place during the visit.

 The lecturer should allow the students to give their on contribution base on their
understanding.

 Finally, the students should be given chance ask questions, where the students will be asking
question associated with the generating station.

ASSIGNMENT:
An assignment should be given to students to write report on the industrial visit, sharing their
experience, knowledge gained and observation.

1
PRACTICAL WORK Week
3
TITTLE: INDUSTRIAL VISIT TO A GAS PLANT POWER STATION

OBJECTIVES:

I. For the students to see how the gas plant power station plant look like.
II. To have a physical look and identification of the different parts of the generating
station.
III. To know how electricity is being generated in the gas power plant

REQUIREMENTS:

1. Students must be familiar with the necessary safety rules.

2. Students must wear all the safety wears before entering the plant e.g.; helmet, safety boot
3. Students must be accompanied by the lecturer teaching the electrical power course while
in the school.

PROCEDURES:

 On arrival at the venue (power station) the lecturer will present an acceptance letter of the
visit to the officer in charge of the industrial visit in the generating station
.
 The officer will appoint the person that will lead the team i.e. the students and the lecturer
into the plant. The officer or leader of the team with start by giving the general
description of the generating station, then move from one part of the station to the other.

 Finally, their should be period for questions and answer, where the students will be
asking question associated with the generating station.
Practical Work Week 4

TITTLE: DISCUSSION ON THE INDUSTRIAL VISIT TO GAS POWER STATION

OBJECTIVES:

I. To determine the level of understanding in the students from the visit.

II. To allow the Students express their feelings and observation with respect to generating
power station (Gas power station).
III. To have an interaction the lecturer concerned to lead them during the visit so as clear
doubtful areas that are clear to the students while in the power station, on which the
could not asked.

REQUIREMENTS:

1. Writing materials such as pencils, biros, etc.

2. Student’s jottings i.e what the students must have jotted down during the visit.
3. Students who visited the Gas power station and the lecturer teaching the electrical power
course while in the school and also accompanied during the visit.

PROCEDURES:

 The lecturer should start by given a general introduction of the discussion of the industrial
visit to the Gas power station.
.
 A general summary of the industrial visit, mentioning what happened from the first point up
to the last point of the activities that took place during the visit.

 The lecturer should allow the students to give their on contribution base on their
understanding.

 Finally, the students should be given chance ask questions, where the students will be asking
question associated with the generating station.

ASSIGNMENT:
An assignment should be given to students to write report on the industrial visit, sharing their
experience, knowledge gained and observation.

1
PRACTICAL WORK Week 5

Solar Energy
Model

TITLE; Solar Energy Model System

Objectives:
 Introduction to Solar Energy Model.
 Effect of the distance and angle on the solar cell's output voltage.
1
PRACTICAL WORK Week 5

Equipment Required:
 Solar Energy Model
 Power supply
 A multimeter
 Connecting leads

Discussion:
Solar energy model consists of several components. Read the following component’s
short description and identify them. In this experiment we will check how distance
and angel affect the solar cell voltage.

 Halogen lamps – 2 halogen lamps (25 watt each) in a lamp house located on a track which
enable to distance the lamp from the solar cell and to change its direction angle.

 Solar cell – The solar cell converts the light on it directly to electric energy. It acts as a
voltage source.

The solar cell house includes two phototransistors and is connected mechanically to an electric
motor by transmission. The motor and the light sensors are connected to an electronic circuit
which enables the solar cell to follow the light source.

 Voltage meter – An electronic circuit which measures the solar cell voltage and lights the
LED correspondingly.

 A motor – A small DC motor on the panel as an example for electrical load.

2
PRACTICAL WORK Week 5
 A buzzer – Another electrical load.

 A lamp – Another electrical load.

 Rechargeable batteries for energy storage.

 A capacitor – used for temporary energy storage and output voltage stabilization.

 Power main switch – turns ON and OFF all the systems of solar energy model.

 The energy source lamps ON/OFF switch.

 An external power supply – converts the Mains voltage to low AC voltage with a dimmer for
linear power changing.

 Digital multimeter.

3
PRACTICAL WORK Week 5

Procedure:
Step 1: Connect solar energy model to the power supply inlet sockets. Connect the power supply
to the Mains.

Step 2: Turn ON the main switch of solar energy model and the lamp switch.

Step 3: Change the power supply slide switch.

The halogen lamps should turn ON.

Step 4: Change the power slide switch in both directions and observe the lamp.

The slide switch has 4 states – 6V, 9V, 12V and 14.5V.

Step 5: Set the slide to 9V.

Step 6: On the rear panel there are two sockets.

Connecting these two sockets with the Connecting leads makes a short circuit and that is
what activates the following electronic circuit.

Connect these two sockets with the Connecting leads.

Check that the solar cell follows the lamps.

Step 7: Change the distance and the angle and observe the solar cell movement.

Step 8: Move the lamp track to angle 0o.

Check that the solar cell is directed to the lamps.

Step 9: Disconnect the Connecting leads from the two sockets on the rear panel in order to
switch OFF the following system.

4
PRACTICAL WORK Week 5
Step 10: The output of the solar cell is connected to the input of the voltmeter located on the
system panel.

We use the 0-5V scale.

Another switch is located on the front panel marked capacitor ON/OFF.

This switch connects and disconnects a capacitor in parallel to the solar cell output.

This capacitor store electrical charges and stabilizes the solar cell output voltage.

Disconnect the capacitor.

Change again the light intensity and the lamps distance and angle and observe the
reaction on the voltmeter.

The lamps current is an Alternate current (AC). That is why the solar cell voltage is
variable. We see it because several lamps are turned ON simultaneously on the
voltmeter panel.

Step 11: Connect the capacitor.

Turn ON its switch.

Change again the light intensity and the lamps distance and angle and observe the
reaction on the voltmeter.

This time only one light at a time turns ON.

When two lights turn ON simultaneously, it means that the measured voltage is on the
range between the two lights’ marks.

5
PRACTICAL WORK Week 5
Step 12: Write down the distance at which the solar output voltage is 3V for different light
intensity.

Light intensity 0 angle 10 angle 20 angle

6V
9V
12V

Intensity 1 is the minimum intensity and intensity 5 is the maximum.

Step 13: As you could see, the output voltage of the solar cell depends on the distance and the
angle too.

Connect the multimeter in a voltage measurement mode at 20V range as follows: the red
probe to the solar cell output socket (ENERGY OUT) and the black probe to the ground
socket (GND). Check that the capacitor switch is in the OFF position.

Step 14: Set the power supply voltage to 9V.

Measure the voltage produced by the solar cell for different distances and angles once
when the distance decreases and once when it increases:

0 angle 10 angle 20 angle

Distance
Up Down Up Down Up Down
90mm
110mm
130mm
150mm
170mm
190mm

6
PRACTICAL WORK Week 5
Step 15: Mark these points on the following graph. Use three different colors for each angle.
Connect these points with lines according to the distance changing course.

Voltage [V]3

0
80 90 100 110 1200 130 140 150 160 170 180 190
Distance [mm]

Step 16: Repeat step 14-15 for the different light intensities of the solar cells.

Step 17: Turn OFF the lamps switch.

7
Practical Work Week 6

TITTLE: DISCUSSION ON THE INDUSTRIAL VISIT TO SOLAR POWER STATION

OBJECTIVES:

I. To determine the level of understanding in the students from the visit.

II. To allow the Students express their feelings and observation with respect to generating
power station (Solar power station).
III. To have an interaction the lecturer concerned to lead them during the visit so as clear
doubtful areas that are clear to the students while in the power station, on which the
could not asked.

REQUIREMENTS:

1. Writing materials such as pencils, biros, etc.

2. Student’s jottings i.e what the students must have jotted down during the visit.
3. Students who visited the solar power station and the lecturer teaching the electrical power
course while in the school and also accompanied during the visit.

PROCEDURES:

 The lecturer should start by given a general introduction of the discussion of the industrial
visit to the Solar power station.
.
 A general summary of the industrial visit, mentioning what happened from the first point up
to the last point of the activities that took place during the visit.

 The lecturer should allow the students to give their on contribution base on their
understanding.

 Finally, the students should be given chance ask questions, where the students will be asking
question associated with the generating station.

ASSIGNMENT:
An assignment should be given to students to write report on the industrial visit, sharing their
experience, knowledge gained and observation.

1
Practical work Week 7

TITLE; – Solar cells Output

Objectives:
 The solar cell’s Electric Motive Force.
 Measurement of the internal resistance.

Equipment Required:
 Solar Energy model
 Power supply
 A multimeter
 Connecting leads

Discussion:
Every voltage source has internal resistance. We can not see this resistance but we can
see its affection. Usually this resistance is marked with the letter r.
The output voltage of an electric battery without any electric load is higher than its voltage when it
is connected to an electric load.

The reason is that the load current flows also through the internal resistance and cause an internal
voltage drop, according to the Ohm's Law:

Vr  I  r

The internal voltage of the electric battery is caused by chemical reaction and is called Electro
Motive Force and is marked by the letter E.

The output voltage is equal to:

V  E  I r

1
Practical work Week 7
The higher the current is and the higher the internal resistance is, the lower the output voltage is.

An 'empty' electric battery means that its internal resistance is so high that its output voltage is very
small for even small currents.

That is the reason why we should check batteries only with electric load.

The solar cell is similar to an electric battery. It has Electro Motive Force (EMF) and internal
resistance. The EMF depends on the light intensity on the solar cell.

The solar cell is made of many small solar cells. Each cell is based on electronic component which
is exposed to light. Light on the solar cell causes the electrons to move from one side of the cell to
the other side. This movement creates excess of electrons in one side and lack of electrons on the
other side and electric voltage (small EMF).

Some of the solar cells are connected in series to create larger EMF. Many chains of cells in series
are connected in parallel to enable high current and power and to decrease the internal resistance.

In this experiment we will measure the Electro Motive Force and the internal resistance of the kit
solar cell.

Procedure:
Step 1: Connect Solar Energy model to the sockets of the power supply. Connect the power
supply to the Mains.

Step 2: Turn ON the main switch of Solar Energy Model.

Step 3: Set the power supply slide switch to 9V.

Step 4: Locate the lamp opposite the solar cell and set the distance to 110mm and the angle to
0.

Step 5: Turn ON the lamp switch.

The lamps should turn ON and light the solar cell.

Step 6: In this experiment we will measure the internal resistance of the solar cell. First measure
the voltage on the solar cell's output with the multimeter.

Vopen-circuit = ________V

This voltage is the Electro Motive force (EMF) of the solar cell.

Step 7: Turn the multimeter into a current measuring mode, 200mA range. Connect it between
the solar cell's output and the ground.
2
Practical work Week 7

Ishort-circuit = _________A

The internal resistance:

Vopencircuit
r = _________
I short circuit

What did we measure here? Every voltage source has an internal resistance, which we
can't see, but can feel its outcome.When a voltage source is not connected to an
electrical consumer, current does not flow through the internal resistor and electrical
voltage is not developed on it (according to the Ohm's Law). Thus the output voltage is
equal to the internal voltage of the source.

EMF Vopen-circuit

Vopen-circuit = EMF

When an electrical consumer is connected to a voltage source, current flows in the

circuit. This current also flows through the internal resistance and causes electrical
voltage to drop on it. The voltage between the source's probes (the voltage that will
reach the consumer) will be equal to the internal voltage (EMF) minus the voltage drop
on the internal resistance.

As bigger the internal resistance is, the voltage that reaches the consumer is smaller. We
wish that the internal resistance will be as small as possible.

When we connect a current meter without an electrical consumer between the solar cell's
probes, we cause all the internal voltage to drop on the internal resistance. It allows us to
measure the internal resistance:

Vopencircuit
r
I short circuit

Step 8: Repeat this measurement for different distances and different levels of intensities and fill
in the following tables:

Internal Resistance r Electro Movie Force EMF

Distance 90 110 130 150 170 Distance 90 110 130 150 170
Intensity Intensity
3
Practical work Week 7
6V 6V
9V 9V
12V 12V

4
Practical Work Week 8

TITTLE: DISCUSSION ON THE SOLAR CELLS OUTPUT

OBJECTIVES:

I. To determine the level of understanding in the student.

II. To allow the Students express their feelings and observation with respect to Solar Cells
output.
III. To have an interaction the lecturer concerned to lead them during the practical so as clear
doubtful areas that are clear to the students while doing the practical, on which the could
not asked.

REQUIREMENTS:

1. Writing materials such as pencils, biros, etc.

2. Student’s jottings i.e what the students must have jotted down during the visit.
3. Students who performed the practical and the lecturer teaching the electrical power course.

PROCEDURES:

 The lecturer should start by given a general introduction of the discussion.

.
 A general summary of the practical, mentioning what happened from the first point up to the
last point of the activities that took place during the practical.

 The lecturer should allow the students to give their on contribution base on their
understanding.

 Finally, the students should be given chance ask questions, where the students will be asking
question associated with the generating station.

ASSIGNMENT:
An assignment should be given to students to write report on the industrial visit, sharing their
experience, knowledge gained and observation.

1
Practical work Week 9

Wind Energy
Model

TITLE; – Power System Generation using Wind Energy Model System

Objectives:
 Introduction to wind Energy model.
 Affect of the distance and angle on the wind electric generator's output voltage.

Equipment Required:
1
Practical work Week 9
 Wind Energy Model
 Power supply
 A multimeter
 Connecting leads

Discussion:
Wind Energy Model consists of several components. Read the following component’s
short description and identify them. In this experiment we will check how distance
and angel affect the electric generator voltage.

 A fan – Used as a wind generator and located on a track which enable to

distance the fan from the wind electric generator and to change its direction
angle.

 A wind electric generator – A motor with a propeller that converts the wind
directly to electric energy. It acts as a voltage source.

 Voltage meter – An electronic circuit which measures the electric generator

voltage and lights the LED correspondingly.

 A motor – A small DC motor on the panel as an example for electrical load. A

lever is located on its axle to create mechanical load.

 A buzzer – Another electrical load.

 A lamp – Another electrical load.

 Rechargeable batteries for energy storage.

 A capacitor – used for temporary energy storage and output voltage

stabilization.

 Power main switch – turns ON and OFF all the systems of Wind Energy Model.

 The energy source lamps ON/OFF switch.

 An external power supply – converts the Mains voltage to low DC voltage with
a slide switch for power changing.

2
Practical work Week 9
 Digital multimeter.

Procedure:
Step 1: Connect Wind Energy Model to the power supply inlet sockets. Connect the
power supply to the Mains.
Step 2: Turn ON the main switch of Wind energy model and the energy source
switch, the fan should rotate.
Step 3: Change the power supply slide switch, the fan speed should change
accordingly.
Step 4: Change the power slide switch in both directions and observe the fan's
speed. The acceleration and deceleration takes time.
The slide switch has 4 states – 6V, 9V, 12V and 14.5V.
Step 5: Set the slide to 9V.
Step 6: The output of the wind electric generator is connected to the input of the
voltmeter located on the system panel.
We use the 0-15V scale.
Another switch is located on the front panel marked capacitor ON/OFF.
This switch connects and disconnects a capacitor in parallel to the wind
electric generator output.

This capacitor stores electrical charges and stabilizes the wind electric
generator output voltage.
Disconnect the capacitor.
Change again the fan speed, distance and angle and observe the reaction on
the voltmeter.
The wind electric generator does not create a stable voltage.
Step 7: Connect the capacitor.
Turn ON its switch.
Change again the fan speed, distance and angle and observe the reaction on
the voltmeter.
This time only one light at a time turns ON.
When two lights turn ON simultaneously, it means that the measured
voltage is on the range between the two lights’ marks.
Step 8: Write down the distance at which the wind electric generator output voltage
is 12V.
Power voltage 0 angle 10 angle 20 angle
9V

3
Practical work Week 9
Step 9: As you could see, the output voltage of the wind electric generator depends
on the distance and the angle too.

Connect the multimeter in a voltage measurement mode at 20V range as

follows: the red probe to the wind electric generator output socket
(ENERGY OUT) and the black probe to the ground socket (GND). Check
that the capacitor switch is in the OFF position.
Step 10: Set the power voltage to 9V.
Measure the voltage produced by the wind electric generator for different
distances and angles once when the distance decreases and once when it
increases:
0 angle 10 angle 20 angle
Distance
Up Down Up Down Up Down
90mm
110mm
130mm
150mm
170mm
190mm

4
Practical work Week 9
Step 11: Mark these points on the following graph. Use three different colors for
each angle. Connect these points with lines according to the distance
changing course.
18

15

12

Voltage [V]9

Step 12: Repeat step 10-11 for the different speeds of the fan.
6

0
80 90 100 110 1200 130 140 150 160 170 180 190
Distance [mm]

5
Practical Work Week
10

TITTLE: DISCUSSION ON THE INDUSTRIAL VISIT TO WIND POWER STATION

OBJECTIVES:

I. To determine the level of understanding in the students from the visit.

II. To allow the Students express their feelings and observation with respect to generating
power station (Wind power station).
III. To have an interaction the lecturer concerned to lead them during the visit so as clear
doubtful areas that are clear to the students while in the power station, on which the
could not asked.

REQUIREMENTS:

1. Writing materials such as pencils, biros, etc.

2. Student’s jottings i.e what the students must have jotted down during the visit.
3. Students who visited the Wind power station and the lecturer teaching the electrical power
course while in the school and also accompanied during the visit.

PROCEDURES:

 The lecturer should start by given a general introduction of the discussion of the industrial
visit to the Wind power station.
.
 A general summary of the industrial visit, mentioning what happened from the first point up
to the last point of the activities that took place during the visit.

 The lecturer should allow the students to give their on contribution base on their
understanding.

 Finally, the students should be given chance ask questions, where the students will be asking
question associated with the generating station.

ASSIGNMENT:
An assignment should be given to students to write report on the industrial visit, sharing their
experience, knowledge gained and observation.

1
Practical Work Week
10

2
Practical Work Week
11

TITLE – Wind Electric Generator Output

Objectives:
 The wind electric generator's Electric Motive Force.
 Measurement of the internal resistance.

Equipment Required:
 Wind Energy Model
 Power supply
 A multimeter
 Connecting leads

Discussion:
Every voltage source has internal resistance. We can not see this resistance but we can
see its affection. Usually this resistance is marked with the letter r.

The output voltage of an electric battery without any electric load is higher than its
voltage when it is connected to an electric load.

The reason is that the load current flows also through the internal resistance and cause
an internal voltage drop, according to the Ohm's Law:

Vr  I  r

The internal voltage of the electric battery is caused by chemical reaction and is called
Electro Motive Force and is marked by the letter E.

The output voltage is equal to:

V  E  I r

The higher the current is and the higher the internal resistance is, the lower the output
voltage is.

1
Practical Work Week
11
An 'empty' electric battery means that its internal resistance is so high that its output
voltage is very small for even small currents.

That is the reason why we should check batteries only with electric load.

The wind electric generator is similar to an electric battery. It has Electro Motive
Force (EMF) and internal resistance. The EMF depends on the wind intensity on the
wind electric generator.

The electric motor is composed of an electromagnet, located on the central axle

(called rotor) and two rainbow shape magnets on the motor's surface.

Electromagnet is an electrical coil, which turn into a magnet when current is flowing
through it.

When current is flowing through the motor's coil, the electromagnet rotor wishes to
arrange itself according to the two magnets on the motor's surface. The South Pole is
attracted to the magnet with the North Pole and the North Pole is attracted to the
magnet with the South Pole.

Fix Fix
Magnet Magnet

Rotor

N S N S N S

As soon as the electromagnet reaches this situation, the current direction in its coil is
changing and it keeps rotating in order to adjust itself to the new situation. The
current changes again and so on. This is how the motor rotates when we supply it with
an electrical voltage.

The larger the voltage, the larger the current, which flows through the coil, the
magnetic gravity will grow and the turning velocity will grow.

2
Practical Work Week
11
When we rotate the shaft of the DC motor mechanically, an electric voltage induces
into the rotor coil.The DC motor acts as an electric generator.

This voltage is the generator EMF and depends on the rotation speed. The EMF
creates an electric current through a load, which connected to the generator poles.

The generator has internal resistance. As we know, the load current depends on the
generator EMF and the internal resistance.

The interesting point is that the internal resistance depends on the load current. This
current flows through the electromagnet coils, turns it into electromagnet, creates
mechanical load and reduces the EMF.

In this experiment, we will measure the Electro Motive Force and the internal
resistance of the kit wind electric generator.

Procedure:
Step 1: Connect Wind Energy Model to the sockets of the power supply. Connect
the power supply to the Mains.

Step 2: Turn ON the main switch of Wind Energy Model.

Step 3: Set the power supply slide switch to 9V.

Step 4: Locate the fan opposite the wind electric generator and set the distance to
110mm and the angle to 0.

Step 5: Turn ON the fan switch.

The fan should rotate, and after some time the wind electric generator
propeller should rotate too.

Step 6: In this experiment we will measure the internal resistance of the wind
electric generator. First measure the voltage on the wind electric generator's
output (ENERGY OUT) with the multimeter.

Vopen-circuit = ________V

3
Practical Work Week
11
This voltage is the Electro Motive force (EMF) of the wind electric
generator.

Step 7: Turn the multimeter into a current measuring mode, 10A range. Connect it
between the wind electric generator's output and the ground.

Ishort-circuit = _________A

The internal resistance:

Vopencircuit
r = _________
I short circuit

What did we measure here? Every voltage source has an internal resistance,
which we can't see, but can feel its outcome.

When a voltage source is not connected to an electrical consumer, current

does not flow through the internal resistor and electrical voltage is not
developed on it (according to the Ohm's Law). Thus the output voltage is
equal to the internal voltage of the source.

EMF Vopen-circuit

Vopen-circuit = EMF

When an electrical consumer is connected to a voltage source, current flows

in the circuit. This current also flows through the internal resistance and
causes electrical voltage to drop on it. The voltage between the source's
probes (the voltage that will reach the consumer) will be equal to the
internal voltage (EMF) minus the voltage drop on the internal resistance.

As bigger the internal resistance is, the voltage that reaches the consumer is
smaller. We wish that the internal resistance will be as small as possible.

4
Practical Work Week
11
When we connect a current meter without an electrical consumer between
the wind electric generator's probes, we cause all the internal voltage to
drop on the internal resistance. It allows us to measure the internal
resistance:

Vopencircuit
r
I short circuit

Step 8: Repeat this measurement for different distances and different levels of
intensities and fill in the following tables:

Internal Resistance r Electro Movie Force EMF

Distance 90 110 130 150 170 Distance 90 110 130 150 170
Intensity Intensity
9V 1
12V 2
14.5V 3

5
Practical Work Week
12

TITTLE: DISCUSSION ON THE WIND ELECTRICAL GENERATOR OUTPUT

OBJECTIVES:

I. To determine the level of understanding in the student.

II. To allow the Students express their feelings and observation with respect to Wind
generator output.
III. To have an interaction the lecturer concerned to lead them during the practical so as clear
doubtful areas that are clear to the students while doing the practical, on which the could
not asked.

REQUIREMENTS:

1. Writing materials such as pencils, biros, etc.

2. Student’s jottings i.e what the students must have jotted down during the visit.
3. Students who performed the practical and the lecturer teaching the electrical power course.

PROCEDURES:

 The lecturer should start by given a general introduction of the discussion.

.
 A general summary of the practical, mentioning what happened from the first point up to the
last point of the activities that took place during the practical.

 The lecturer should allow the students to give their on contribution base on their
understanding.

 Finally, the students should be given chance ask questions, where the students will be asking
question associated with the generating station.

ASSIGNMENT:
An assignment should be given to students to write report of the practical, sharing their experience,
knowledge gained and observation.

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TITLE: Disassembling and re-assembling Protective Device

Protective Device
We will choose the circuit breaker as protective device and the contactor as control
device.
Circuit breaker
Circuit breaker is used to protect any electrical installation from the danger of
over currents.
 Introduction

Circuit breaker is a piece of equipment

which is designed to protect an electrical
apparatus from damage caused by overload or
short circuit. Unlike a fuse which operates
once and then has to be replaced, a circuit
breaker can be reset (either manually or
automatically) to resume normal operation.

Circuit breakers are often implemented

with a solenoid (electromagnet) whose
strength increases as the current increases and
eventually trips the circuit breaker. 5. Bimetallic strip
1. lever
6. adjusting screw
Alternatively a bimetallic strip may be used 2. lever mechanism
7. Solenoid
3. Contacts
which heats and bends with increased current. 8. Arc divider
4. Terminals
Some circuit breakers incorporate both Figure 1 : Construction of the circuit
techniques. This allows the properties of the breaker
circuit breaker to be tailored to suit the

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application, with the electromagnet generally responding to short, large surges in current
(short circuit) and the bimetallic strip responding to smaller but longer-term (overload) over
current conditions, the construction of circuit breaker is shown in figure

 Apparatus

1. One circuit breaker.

2. Tools box

 Procedure :
o Disassembling the circuit breaker
o Identify the all parts of the circuit breaker as shown in figure (5-1).
o re-assembling the circuit breaker

Use the Circuit breaker in the protected circuit

 Introduction

To discriminate between the current the circuit breaker can handle and the current it
has to interrupt.

 Apparatus

3. 15 rating circuit breaker.

4. 0 to 100 £1 variable resistors (high power rating).
5. 240 V ac power supply.
6. Connecting wires.
7. Ammeter.

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 Procedure :
1. Connect the circuit as shown in fig. (4-2).

supply
Circuit
breaker
I>

Figure 2: circuit diagram of the protected circuit

2. Put the resistance (R) at its maximum value, and then turn on the power supply.
3. Perform the adequate variation of the circuit breaker rating before any alte-
ration of the load resistance, according to the above table. Close the circuit
breaker.
4. Start from full resistance to zero resistance, decreasing it in 10 steps.
5. Fill, in table in your worksheet, the circuit breaker tripping time, until you reach zero
resistive loads.
6. Turn off the system, by opening the circuit breaker.
7. Put the load resistance 'to zero, then turn "ON" the circuit breaker and note the
tripping time.

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Solve the following questions:
1. Calculate the various values of current (I) if
we are to start from full resistance to zero Tripping
Current Resistance
resistance, decreasing it in 10 steps. Tabulate Time
(Amps) (Ohms)
(seconds)
the values obtained in table (5-1).

Table 1

2. Write your own conclusion regarding the mechanisms that tripped the circuit
breaker in step 5 and in step 7.

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TITLE: CABLE TESTING AND FAULT LOCATION

OBJECTIVE:
To determine the type & position of various faults on a model 3-core distribution cable

APPARATUS:
A Wheatstone bridge
An Ohmmeter
10.8 Ohm rheostat
6-km cable located in laboratory bench
(The circuit for this is shown in Fig. 1.It contains four 120-ohm resistors for each phase as shown in
the Figure. Each 120-ohm resistor represents 1.5 km of the cable length) 20 V DC Power Supply

THEORY:
When fault finding, an engineer would have access to the terminals at the sending and
receiving ends of a cable. He may also have access to a joint box where two sections
of each phase could be separated. A measuring bridge could therefore be connected at
any set of 3 phase terminals but could not be connected at intermediate points
between the terminal sites and the joint box.
The bridge comprises three pairs of accurately adjusted non-inductive ratio arms and
a four-decade variable resistance for balancing purposes.
A sensitive galvanometer is incorporated which is protected by diodes against
accidental overloads and a variable sensitivity switch in series with the galvanometer
is also fitted.
Range of measurement: 0 to 1.111 Megs
It can be shown that the bridge equation is
R1/R2 = Rx/R3
Where R1 and R2 are the "ratio arms"
R3 is the 4-dial variable resistance
Rx is the unknown resistance.
A DC supply of 2 Volts in series with a protective resistor of 10.8 ohms is required
for the bridge.
A null balance is obtained by adjustment of the four-decade variable R3 and
observing the movement of the detector.
The detector only works when the press switch is depressed, and turning the
sensitivity control clockwise may increase the sensitivity of the galvanometer.
Table of setting for various ranges of Rx
Rx ohms R1 ohm R2 ohm
If necessary, the bridge may be supplied from an Ac source and used with an
oscilloscope as a detector.
Procedure:
Use the ohmmeter to check the continuity and phase connections. Prepare a table to
receive your results and your comments on the type of fault for each test.
Test 1
Use the Wheatstone bridge to find the resistance of each conductor and thus the
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resistance per meter run of he cable. FIG.2
The galvanometer resistance should be anti-clockwise at the beginning of each test
Why? Set the supply voltage to 2 V. What is the purpose of the 10.8-ohm rheostat?
Test 2 Single-line to ground fault
1. Join terminal A to E. Check each phase for ground and between ohase for a short.
Which phase has a fault? What is the type of fault?
2. Find the resistance from the sending end to the fault. FIG.3. Use the resistance per
meter, r to find the distance to the fault.
3. Connect B to E with the fault resistance and check the type of fault.
R2/R3 = R1/Rx
(R2+R3)/R3 = (R1+Rx)/Rx = 2r/Rx
Therefore, Rx = 2r R3/(R2+R3)
Test 3 Line- to- Line fault
Join C to D with the fault resistor. Identify the faulty phases and establish the type of
fault. Find the distance to the fault. FIG.4
Test 3 Line- to- Line fault
For a line to line fault in phases Y & B,
Rx = 2r.R3/(R2+R3).
For a line to line fault in phases R & Y, the circuit of FIG.4 should be appropriately
changed, and then
Rx = 2.r. R2/(R2+R3)
Test 4 Three-phase fault
Link C, D and B. Identify the faulty phases and establish the type of fault. Find the
location of the fault. FIG.5. 2Rx = R1
R3 R2

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TITLE: Short Transmission Line - Equivalent circuit and Phasor diagram

Short Transmission Line

The equivalent circuit and vector diagram of a short transmission line are

shown in the figure given below.In the

equivalent circuit short transmission line is represented by the lumped
parameters R and L. R is the resistance (per phase) L is the inductance (per
phase) of the entire transmission line.As said earlier the effect of shunt
capacitance and conductance is not considered in the equivalent circuit.The line
is shown to have two ends : sending end (designated by the subscript S) at the
generator, and the receiving end (designated R) at the load.

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The phasor diagram is drawn taking Ir, the receiving end current as the reference.

The terms with in the simple brackets is small as compared to unity, using
binomial expansion and limiting only to second term
Vs ≈ Vr + IrR cosΦr + IrX sinΦr

Here Vs is the sending end voltage corresponding to a particular load current

and power factor condition. It can be seen from the equivalent circuit that the
receiving end voltage under no load is same as the sending end voltage under
full load condition i.e Vr(no load) = Vs . Therefore

where Vr and Vx are the per unit values of resistance and reactance of the
line.From the equivalent circuit diagram we can observe that
Vs = Vr + Ir ( R + jX) = Vr + IrZ
Is = Ir

In a four terminal passive network the voltage and current on the receiving end
and sending end are related by following pair of equations
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Vs = AVr + BIr
Is = CVr + DIr

Comparing the above two sets of equations, for a short transmission line A =
1, B = Z, C = 0, D = 1. ABCD constants can be used for calculation of
regulation of the line as follows:

Normally the quantities P,Ir and cosΦr at the receiving end are given and
ofcourse the ABCD constants.Then determine sending end voltage using the
relation Vs = AVr + BIr. Vr(no load) at the receivind end is given by Vs/A

when Ir = 0.

Classification of transmission lines Classification of

transmission lines
Transmission lines are classified as short, medium and long. When the length
of the line is less than about 80Km the effect of shunt capacitance and
conductance is neglected and the line is designated as a short transmission
line. For these lines the operating voltage is less than 20KV.
For medium transmission lines the length of the line is in between 80km -
240km and the operating line voltage wil be in between 21KV-100KV.In this
case the shunt capacitance can be assumed to be lumped at the middle of the
line or half of the shunt capacitance may be considered to be lumped each end
of the line.The two representations of medium length lines are termed as
nominal-T and nominal- π respectively.
Lines more than 240Km long and line voltage above 100KV require calculations
in terms of distributed parameters.Such lines are known as long transmission
lines.This classification on the basis of length is more or less arbitrary and the
real criterion is the degree of accuracy required.

Performance of Transmission Lines - Efficiency and Regulation

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Performance of Transmission Lines
The performance of a power system is mainly dependent on the performance of
the transmission lines in the system.It is necessary to calculate the
voltage,current and power at any point on a transmission line provided the
values at one point are known.

The transmission line performance is governed by its four parameters - series

resistance and inductance,shunt capacitance and conductance.All these
parameters are distributed over the length of the line.The insulation of a line is
seldom perfect and leakage currents flow over the surface of insulators
especially during bad weather.This leakage is simulated by shunt
conductance.The shunt conductance is in parallel with the system
capacitance.Generally the leakage currents are small and the shunt
conductance is ignored in calculations.
Performance of transmission lines is meant the determination of efficiency and
regulation of lines.The efficiency of transmission lines is defined as

The end of the line where load is connected is called the receiving end and
where source of supply is connected is called the sending end.

The Regulation of a line is defined as the change in the receiving end voltage,
expressed in percent of full load voltage, from no load to full load, keeping the
sending end voltage and frequency constant.