PSZ 19:16 (Pind. 1/07)
UNIVERSITI TEKNOLOGI MALAYSIA
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND
COPYRIGHT
Author’s full name :
MUHAMMAD FAISAL HASSAN BIN ISMAIL
Date of birth
:
DICEMBER 9th 1989
Title
:
AUTOMATIC RECLOSE EARTH LEAKAGE CIRCUIT BREAKER
Academic Session :
2011/2012
I declare that this thesis is classified as:
CONFIDENTIAL
(Contains confidential information under the
Official Secret Act 1972)*
RESTRICTED
(Contains restricted information as specified by
the organization where research was done)*
OPEN ACCESS
I agree that my thesis to be published as online
open access (full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows:
1. The thesis is the property of Universiti Teknologi Malaysia.
2. The Library of Universiti Teknologi Malaysia has the right to make copies
for the purpose of research only.
3. The Library has the right to make copies of the thesis for academic
exchange.
Certified by:
SIGNATURE
SIGNATURE OF SUPERVISOR
891209-14-5625
(NEW IC NO. /PASSPORT NO.)
DR. MOHD FADLI BIN RAHMAT
NAME OF SUPERVISOR
Date: 20th JUNE 2012
Date: 20th JUNE 2012
NOTES :
*
If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the
letter from the organisation with period and reasons for
confidentiality or restriction.
AUTOMATIC RECLOSE EARTH LEAKAGE CIRCUIT BREAKER
MUHAMMAD FAISAL HASSAN BIN ISMAIL
A report submitted in partial fulfillment of the
requirements for the award of the degree of
Bachelor of Engineering
(Electrical)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
JUNE 2012
ii
“I hereby declare that I have read this thesis and in my
opinion this thesis is sufficient in terms of scope and quality for the
award of the degree of Bachelor of Engineering
(Electrical)”
Signature
:
............................................
Name of Supervisor : DR. MOHD FADLI BIN RAHMAT
Date
: 20th JUNE 2012
iii
“I declare that this thesis entitled “Automatic Reclose Earth Leakage Circuit
Breaker” is the result of my own research except as cited in the references. The
thesis has not been accepted for any degree and is not concurrently submitted in
candidature of any other degree.”
Signature
: ....................................................
Name
: MUHAMMAD FAISAL HASSAN BIN ISMAIL
Date
: 20th JUNE 2012
iv
Specially dedicated
to my beloved mother, father, brothers, sisters,
to others who encouraged and helped,
and who inspired me
throughout my journey of education
v
ACKNOWLEDGMENT
Alhamdulillah. Thanks to the Almighty Allah S.W.T, for His blessings and
guidance for giving me inspiration and strengths to complete this project with good
health until the last day of the project report has been submitted.
First and foremost, I would like to express my appreciation to my supervisor,
Dr. Fadli Bin Rahmat who has helped me a lot in giving me ideas, opinions and
valuable comment in the making of this project. I am deeply grateful to have him as
my supervisor and also my mentor. His guidance and supervision will help me in the
future life.
Last but not least, thanks to everyone who involved directly or indirectly in
completing this project either opinion, advice or support from the beginning of the
project until its completion. Thank You So Much
vi
ABSTRACT
Earth Leakage Circuit Breaker (ELCB) is a protective device that used to
isolate the faulty area from power supply when fault current occurred. For home
appliance, ELCB are used to protect the user from electrical shock that caused by
fault current by disconnecting the power supply. The fault current can occur due to
lightning or short circuit from line to ground when someone accidently touches the
energized part of the circuit. Therefore ELCB are designed to trip and isolate this
fault fast enough to prevent the lethal shock. But, the current ELCB that are
implemented at home cannot turn on automatically and need to turn on manually.
Therefore the idea to create an automatic reclose device for ELCB come from this
problem and the design to overcome this problem has been developed. This thesis
will present the development of automatic reclose device for ELCB that will
differentiate between permanent fault current and temporary fault current.
vii
ABSTRAK
Alat Pemutus Litar Bocor ke Bumi (PLBK) adalah salah satu alat
perlindungan yang digunakan untuk memisahkan kawasan kesilapan daripada
sumber bekalan kuasa apabila kesilapan arus berlaku. PLBK yang digunakan untuk
aplikasi kediaman melindungi pengguna daripada kejutan elektrik yang disebabkan
oleh kesilapan arus dengan memutuskan bekalan kuasa. Kesilapan arus boleh berlaku
disebabkan oleh kilat atau litar pintas daripada wayar hidup ke bumi apabila
seseorang menyentuh litar aktif secara tidak sengaja. Oleh itu, PLBK direka untuk
terbelantik dan memisahkan kesilapan ini sepantas yang boleh demi menghalang
kejutan yang boleh membawa maut. Tetapi, PLBK yang ada sekarang tidak boleh
dihidupkan secara automatik dan perlu dihidupkan secara manual. Idea untuk
mencipta alat penghidup automatik datang daripada masalah ini dan rekaan untuk
mengatasi masalah ini telah pun dibangunkan. Tesis ini akan membentangkan
tentang pembangunan alat penghidup automatik untuk PLBK yang voleh
membezakan kesilapan arus kekal dan kesilapan arus sementara.
viii
TABLE OF CONTENTS
CHAPTER
I
II
TITLE
PAGE
SUPERVISOR’S DECLARATION
ii
AUTHOR’S DECLARATION
iii
DEDICATION
iv
ACKNOWLEDGEMENT
v
ABSTRACT
vi
ABSTRAK
vii
TABLE OF CONTENTS
viii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF ABBREVIATIONS
xv
LIST OF APPENDICES
xvi
INTRODUCTION
1.1
Background of Study
1
1.2
Research Objectives
2
1.3
Research Scope
3
1.4
Report Outline
4
LITERATURE REVIEW
2.1
Introduction
5
ix
2.2
Circuit Protection Device
7
2.2.1
Fuses
7
2.2.2
Transducer
8
2.2.3
Relays
10
2.2.4
Circuit Breaker
11
2.2.4.1
Oil Circuit Breaker
12
2.2.4.2
Air Blast Circuit
Breaker
2.2.4.3
Vacuum Circuit
Breaker
2.3
III
13
Earth Circuit Leakage Breaker
14
2.3.1
Voltage Operated Circuit Breaker
15
2.3.2
Current Operated Circuit Breaker
17
2.4
ELCB Construction
18
2.5
Electrical Fault
20
2.6
Previous Project
22
METHODOLOGY
3.1
3.2
3.3
IV
12
RC Servo Motor
23
3.1.1
Servo Power
26
3.1.2
Servo Speed
26
3.1.3
Servo Torque
27
3.1.4
Servo Wire Connection
27
Device Component
29
3.2.1
PIC Micro Controller 18F4550
29
3.2.2
Voltage Regulator LM7805
32
3.2.3
Crystal Oscillator
33
Hardware Development
34
CIRCUIT OPERATION AND DISCUSSION
4.1
Introduction
35
4.2
Project Flow
36
4.3
Circuit Design
37
x
4.4
V
Micro Controller PIC 18F4550 Operation
38
4.4.1
PIC Programming
38
4.4.2
Pulse Width Modulation
41
4.5
Circuit Operation
42
4.6
Result
44
4.7
Discussion
45
CONCLUSION AND RECOMMENDATION
5.1
Conclusion
46
5.2
Recommendation
47
REFERENCE
48
APPENDIXES
51
xi
LIST OF TABLES
xii
LIST OF FIGURES
FIGURE
TITLE
PAGE
2.1
Fuse
7
2.2
Typical Fuse Derating Curve
8
2.3
Current Transformer
9
2.4
Voltage Transormer
9
2.5
Electronic Overcurrent Relay
10
2.6
Circuit Breaker
11
2.7
Oil Circuit Breaker
12
2.8
Air Blast Circuit Breaker
13
2.9
Vacuum Circuit Breaker
14
2.10
Earth Leakage Circuit Breaker
14
2.11
TT Earthing System
15
2.12
Voltage Operated ELCB
16
2.13
Earth Leakage Using An Electrode
16
2.14
Current Operated ELCB
18
xiii
2.15
ELCB Schematic Diagram
2.16
ELCB is Taken Core Balanced Operated
18
Method With an Amplifier
20
3.1
Servo Motor
24
3.2
Servo Component and Servo Internal Part
24
3.3
PWM Waveform
25
3.4
Servo Speed
26
3.5
Servo Torque
27
3.6
Servo Connection
28
3.7
Servo Wire Code
28
3.8
PIC
30
3.9
Interface Using MPLAB IDE
30
3.10
PIC 18F4550
31
3.11
Voltage Regulator LM7805
32
3.12
Voltage Regulator Schematic Diagram
32
3.13
Schematic Diagram
33
3.14
Typical Capacitor Value
33
3.15
Flow Chart Of the Overall Project Implement
34
4.1
Circuit Operation Block Diagram
36
4.2
Circuit Design
37
4.3
PWM Input Signal
42
xiv
4.4
Operation Flow
43
4.5
Hardware Design
44
xv
LIST OF ABBREVIATIONS
TNB
-
Tenaga Nasional Berhad
ELCB
-
Earth Leakage Circuit breaker
PIC
-
Peripheral Interface Controller
RCD
-
Residual Current Device
DC
-
Direct Current
AC
-
Alternating Current
V
-
Voltage
RC
-
Radio Control
IC
-
Integrated circuit
S
-
Signal
PWM
-
Pulse Width Modulation
ms
-
Mili seconds
oz
-
ounces
lbs
-
pound
MCU
-
Microcontroller Unit
MHz
-
Mega Hertz
gnd
-
ground
-
xvi
LIST OF APPENDICES
APPENDIX
TITLE
A
RC Servo C36R User‟s Manual
B
PIC 18F4550 Data Sheet
C
Why Electronic not Electromechanical
ELCB
1
CHAPTER I
INTRODUCTION
1.1 Background of Study
Tenaga Nasional Berhad (TNB) has stated that each premise and building
needs to equip with over current protection device for the safety. In Malaysia, Earth
Leakage Circuit Breaker (ELCB) was used widely as the protection device for
current fault. ELCB is one of the important electrical devices to protect the load
when temporarily damage or permanent earth leakage occurred that would lead to the
short circuit [1].
Earth Leakage Circuit Breaker is an electrical device that can detect the
unbalanced current between the live conductor and neutral conductor hence
disconnect the circuit [2]. ELCB one of the protective device in electrical power
system that help to prevent electric shock to human. If there were any current leakage
to the earth from any electrical device, it will cut off the supply off to the house [2].
2
The „blackout‟ or the cut off electrical supply for such a long time will cause
a trouble for electrical users. It becomes even worse when the users are away or not
at home for a long time. This will caused to the problem of the damage of food in the
refrigerator or the death of fish in an aquarium and malfunction of security alarm.
These are the reasons why it is so important to have the automatic reclosed ELCB
implemented in our home.
Without automatic reclosed ELCB in our market nowadays have give, the
negative effect to the users especially in the industrial sector which electricity is the
life for their business. Therefore, the continuously electrical supplies are important to
make sure that our daily routine do not disturb. The aim of this project is to design
and develop a unit of auto reclosed ELCB that can differentiate and act differently
with different types of fault. The ELCB will trip if current fault occurred.
There are two types of fault. Temporarily fault and permanent fault.
Temporarily fault is caused by lightning strike and the ELCB will close back
automatically after 60 seconds. Permanent fault are caused by short circuit to the
ground by electric device or human. The ELCB close the switch automatically two
times and then stop the operation. This will indicates the permanent error had been
detected. Therefore, the fault needs to repair first before the ELCB will close again
[3].
1.2 Research Objectives
The first objective of this project is to study and understanding the operation
of automatic reclosed with Earth Leakage Circuit Breaker (ELCB). The function of
automatic reclosed is to pull up the ELCB switch during tripping to close the circuit.
3
The second objective is to design and build a driver for auto reclosed ELCB.
The driver was built by the electronic component that will function to pull up the
ELCB switch automatically. To achieve this objective, servo motor and mechanical
concept is used.
The last objective is to minimize the electrical disturbance due to the ELCB
tripping. Electrical disturbance is one of the problems that commonly occurred at
residential area. By implementing the automatic reclosed ELCB at our home, the
electrical disturbance can be minimizing.
1.3 Research Scope
The scope of this project is to design a circuit as simple as possible that can
be implemented at home. To achieve that, the used of smaller and cheaper
component are needed to reduce space and cost but highly safety. The driver must
be small enough to put at a small place and does not need too much space.
The project we focused on ELCB that will implemented at single-phase home
user, which used 240 V input voltage and have the current rating 60 ampere. The
servo motor used must be strong enough to pulled up the ELCB switch. To pull up
the ELCB switch, it must have the pulled force of 3kg and pull stroke about 20 mm.
4
1.4 Report Outline
Chapter I will explain about the early process before begin the project. It
includes the project background, research objectives, scope of project and thesis
outline. Project background is about ELCB and the problem related to it. Research
objectives are the target to resolve the problem. Scopes of project are the limitation
of problem to solve.
Chapter II will explain about the literature review. The explanation are about
the protective device that used in the power system, types of circuit breaker, types of
ELCB and the types of fault current occurred. The function of ELCB was also
explained in detail.
Chapter III will discuss about the methodology that are used to solve the
problem. The explanations are including the types of component used to solve the
problem, their function in detail and the operation of the component to achieve the
research objective.
Chapter IV will explain about the development of automatic reclose device.
The explanations include the operation of the circuit design, the function of servo
motor and how the PIC will control the entire device operation. This chapter also
discuss about the result obtain and the problem that encountered during the making
of device.
Chapter V will explain about the conclusion that had been made from the
result obtain. Also the recommendation on future research to produce a perfect
automatic reclose device for ELCB at home.
5
CHAPTER II
LITERATURE REVIEW
2.1 Introduction
Safety and protection is the important aspect in our life. There are so many
ways to protect ourselves from danger. In other way, we might know the danger that
will come to us but we do not have the ability to fell the presence of electricity and
the danger that we will encountered. This is because electric current are fast and flow
like a surge. We are lucky because there is a regulation nowadays that was made to
ensure the safety in using electricity [11-13].
Based on IEEE Standard Dictionary of Electrical and Electronic Terms,
fourth edition, the definition of „protection system‟ is The electric and mechanical
devices and circuitry, from sensors of the process variable to the actuation device
input terminal, involves in generating those signals associated with the protective
function [18]. Meanwhile, „protective function‟ gives the meaning of The sensing of
one or more variables associated with a particular generating station condition, the
signal processing, and the initiation and completion of the protective action at values
of the variables established in the design bases [18]. Furthermore, the definition of
6
„protective action‟ is the initiation of the operation of a sufficient number of
actuators to affect a protective function [18].
The function of protective equipment is to cause prompt removal from
service of any network element which suffering from abnormal manner that may
cause damage to electrical installation. Abnormal manner is a condition when an
event occurs that causes the operation of any system component to exceed its normal
operating limits. The protection system is another engineering system designed not to
prevent faults but to respond to their occurrence and minimized their effects [13-18].
There are so many method and technique created to protect user from
electricity danger. These protective electrical systems are available in variety shape
from fuse until circuit breaker. Circuit breaker that are commonly used can isolate
the load system from damaged that might be happened. So far, circuit breaker are
widely used and become the solution in electrical protective system [12].
It should realise that protective equipment can minimize [13]: -
1.
The cost of repairing the damage
2.
The speed of fault to other equipment causing damage from
overheating and abnormal mechanical forces.
3.
The time equipment is out of service.
4.
The loss in revenue.
7
2.2 Circuit Protection Device
Circuit protection device are used to protect wires and connectors from being
damaged by excessive current flow caused by over current or short circuit. The
examples of circuit protective devices are fuses, fuse elements, fusible link, and
circuit breaker. There are available in variety of types, shapes, and specific current
rating [10].
2.2.1 Fuses
Figure 2.1: Fuse
Fuse is a type of low resistance resistor that functions to provide over current
protection for load or source circuit. A fuse also a combination of protective device
and circuit breaker. It is the most common protection device and places in an
electrical circuit. The fuse will blows out when the current flow exceeds its rating.
The excessive current will be due to short circuit, overloading mismatched loads or
device failure [13].
8
Figure 2.2: Typical Fuse Derating Curve
The fuse element will melt, opening the circuit and preventing other
component of the circuit from being damaged by the over current. The excessive
current will caused excessive heat. This excessive heat will melt the fuse element.
The rating of the fuse will be determined by the size of the metal element. Fuses are
protective device that only can be used once. After blown, they need to be replaced.
Figure 2.2 showed the typical derating curve for fuse that used to determine the fuse
rating [7].
2.2.2 Transducer
The current transformer (CT) will reduced the high magnitude primary
current to values suitable for relay operation. CT essentials to insulate the secondary
(relay) circuit from the primary (power) circuit and provide currents in secondary,
which are proportional to those in the primary. The primary winding of CT carries
the actual power system current, which is connected to the load [13].
9
Figure 2.3: Current transformer
In case of high voltage system, it is not possible to connect the voltage coil of
the protective device directly to the system. Therefore, it is necessary to step down
the voltage and insulate the protective equipment from the primary circuit. This can
be achieved by using voltage transformer or which is similar to a power transformer
[13].
Figure 2.4: Voltage transformer
10
2.2.3 Relays
Relay is a protective device that functions to isolate a faulty section with the
least interruption to service by controlling the circuit breaker when fault occurred.
Therefore, the relay must be able to detect and to measure abnormal condition and
close the contacts in the tripping circuit [13].
Figure 2.5: Electronic Overcurrent Relay
Overcurrent relay will operates when its current exceeds a predetermined
value. It can be instantaneous and not inherently directional. Differential relay is
intended to respond to the difference between incoming and outgoing electrical
quantities associated with the protective apparatus. Directional relay responds to the
relatives phase position of current with respect to another current [18].
11
2.2.4 Circuit Breaker
Figure 2.6: Circuit Breaker
Circuit breaker is an electrical switch that operated automatically to protect
electric circuit from damage caused by overload or short circuit. It function is to
detect a fault condition and disconnect the current flow immediately. Unlike fuse,
circuit breaker can be reset to resume the normal operation. Circuit breaker is
available in variety size from small size for domestic appliances up to large
switchgear to protect high voltage circuit. A circuit breaker has two contacts, a fixed
contact, and a moving contact. Under normal condition, these two contacts remain in
closed position. When the circuit breaker is required to isolate the faulty part, the
moving contact moves to disrupt the circuit [4].
12
2.2.4.1 Oil Circuit Breaker
Commonly used for voltages up to 300 kV, oil circuit breaker was designed
in two types, dead-tank, and live-tank. The steel tank in dead-tank breaker is partly
filled with fluid. On the top of the tank, there are mounted porcelain bushings to
provide insulation from line voltage to the ground tank. The bushing also permits the
connection of the high-voltage element to the breaker element submerged in the oil
[18].
Figure 2.7: Oil Circuit Breaker
2.2.4.2 Air blast circuit breaker
Air blast circuit breaker is suitable for high current interruption at low
voltage. Air at atmospheric pressure is used as an arc-extinguishing medium. It
occupy to pairs of contact, main contact and arcing contact. The main contact carries
13
current when the breaker is closed. It will separate first when the contact is opened
while the arching contact remains closed. The current then shifted to the arching
contact from the main contact. The arching contact separate later and the arc are
drawn between them [13-15].
Figure 2.8: Air Blast Circuit Breaker
2.2.4.3 Vacuum Circuit Breaker
Vacuum circuit breaker is very simple and compact that power required to
close and open its contact is much less compare to other breaker. Without producing
excessive transient overvoltage, it is capable of interrupting capacitive and small
inductive current. The advantages of vacuum circuit breaker are like suitable for
repeated operation, least maintenance, silent operation, long life, high speed of
dielectric recovery, and less weight of moving part [13-14].
14
Figure 2.9: Vacuum Circuit Breaker
2.3 Earth Leakage Circuit Breaker
An Earth Leakage Circuit Breaker (ELCB) is a device used to detect current
leaking to earth from electrical installation and cut the power supply. It will detect
fault current from live to the earth (ground) wire within the installation it protects. It
also will switch off the power if sufficient voltage appears across the ELCB‟s sense
coil and remain off until manually reset. The purpose of ELCB is to prevent humans
and animal to get injury from electric shock [1-2].
Figure 2.10: Earth Leakage Circuit Breaker
15
ELCB were mainly used on TT earthing system. Most ELCB nowadays are
replaced by Residual Current Device (RCD) especially in the new construction [3].
The first design ELCB only responded to sine wave fault current, but not to rectified
fault current. Disadvantages of ELCB over RCD are they are less sensitive to fault
condition therefore having fewer nuisance trips [6-8].
Figure 2.11: TT Earthing System
2.3.1 Voltage Operated ELCB
Introduced in the early 20th century, voltage operated ELCB have provided a
major advanced in safety for main electrical supplies with inadequate earth
impendence. It detects the increasing in potential between the protected
interconnected metalwork and a distant isolated earth reference electrode. ELCB also
has a second terminal for connecting to the ground. This terminal was connected to
the earth rod that passes through the ELCB by connecting to its two earth terminals.
One terminal goes to the earth wire and the other terminal goes to other type earth
connection. [6]
16
The voltage operated ELCB cannot be used anymore because it lack of
compatible and efficiency. The installation of voltage operated ELCB was very
difficult, which the electrode must be cultivated far away from other metal that will
reduce the efficiency of ELCB to react [6-7].
Figure 2.12: Voltage Operated ELCB
Figure 2.13: Earth Leakage Using an Electrode
17
This system commonly used in a places, which grounding is very high but
earth loop impedance value should not more than 5 ohms (for housing). The leakage
current will flow into the coil in operation and continued to E1, when there is leakage
current between the conductor and the earth in the voltage exceeds 45V. The
operating coil will become a complete circuit and draw switch breaker circuit to the
position “off” and disconnect the supply. A direct connection with the resistance R
will be created when the test switch is pressed. Switch test is used to test the circuit
breaker still operated or not. To ensure the operation of this circuit is always in a
state of good or efficient, this test should be performed monthly [4-6].
2.3.2 Current Operated ELCB
Commonly called Residual Current Device (RCD), current operated circuit
breaker will disconnect a circuit whenever it detects than the electric current is not
balanced between the energized conductor and the return neutral conductor [6-8].
This imbalanced indicate that someone has accidently touching the live part of the
circuit and the current leakage through this body, which is grounded. The result of
these conditions is the lethal shock. This device was designed to disconnect quickly
enough to prevent injury caused by the shock. Current operated ELCB also can
disconnect the circuit when there is over current due to lightning strike and short
circuit conditions [7].
In normal condition, the current flow in the neutral and live conductor is
same. Therefore, no flux will produce. However, if there is the leakage current to the
earth, the current will flow through earth coil and not flow through the neutral
conductor. Flux will produce and the voltage in the secondary coil will triggered a
signal to cut off this electrical system [11-12].
18
Figure 2.14: Current Operated ELCB
2.4 ELCB Construction
Figure 2.15: ELCB Schematic Diagram
19
Electrical appliance and device are manufactured using different material.
Some of these substances are good material and some are good conductor of
electricity. This is the reason many types of ELCB were invented. Nowadays, most
of the ELCB available at home are the „core balanced‟ type [4].
A „toroid‟ (wire wound around an iron ring) has the Active & Neutral
conductors passing through the centre of it. If the current in one wire does not match
the current in the other, a secondary current (the toroid is a current transformer & not
a voltage transformer) is produced at the terminals of the toroid, which is then used
to activate the trip mechanism. ELCB are generally available for two wire, three
wire, & four-wire system in arrange of tripping current and tripping speed. For home
application, there will be either two wires or four-wire system [9].
(a)
20
(b)
Figure 2.16: (a) and (b) ELCB is taken core balanced operating method
with an amplifier
The vector quantity of the current flowing in each phase becomes Ia + Ib + Ic
= 0 if there is no leakage of electricity in the equipment and no voltage will be
induced in the secondary winding of the zero phase current transformer (same result
even when the current of each phase is not in balanced). However, if the ground fault
occurred due to the failure of insulation of the equipment and circuit, vector quantity
of the current will be Ia + Ib + Ic = Ig, thus including a voltage equivalent to Ig in the
secondary winding of the ZCT. This voltage is very small that it cannot trip the
ELCB directly. Therefore, it will feed to the amplifier, excites the shunt trip coil, and
activates the ELCB [6].
2.5 Electrical Fault
The abnormal situation in electrical system in which the current may or may
not flow through intended part. Equipment failure also attribute to some defect in the
circuit, for example are loose connection, insulation failure, or short circuit. A fault
21
which current flow bypasses the normal load is called short circuit fault. An open
circuit fault occurs if a circuit is interrupted by some failure [13].
The fault current that occurs in power system is usually large and dangerous.
The short circuit fault are the commonest and most damaging since the excessive
current will cause thermal and mechanical damaging to the plant carrying it. The
occurrence of fault cannot be prevented because of aging, human error and external
interference [13].
Faults can damage or disrupt power systems in several ways [13-15]:-
1.
Large faults current will cause overheating of power system
component.
2.
The extremely high temperature in arc due to short circuits will
aphorized any known substances, causing equipment destruction.
3.
The system voltage can be lowered or raised outside their acceptable
ranges.
4.
Three-phase system can become unbalanced thus causing three phases
to operate improperly.
5.
Faults block the flow of power
6.
Faults can cause the system to become unstable and „break up‟
22
2.6 Previous Project
For previous project, the researcher had made a research about the force that
is needed pulled the ELCB switch. These devices have to convert from high AC
voltage to low DC voltage, very costly and inefficient due to battery supply. He
successfully completed the project and creates the automatic reclosed ELCB but this
device will continuously on the ELCB after tripping [9-10].
The second researcher had improved the device by adding one timer,
therefore will operate to switch the ELCB based on times only. If the ELCB tripped
more than two times, a permanent fault is assumed to be occurred. Although the
device had been improved, the device still needs to convert the high AC voltage to
low DC voltage [11].
The third researcher also creates the automatic reclosing ELCB that the
device will switch on the ELCB two times after tripping and manage to reduced his
project cost by using battery as the main supply. Nevertheless, the ac input voltage
still used as input supply for motor. In his design, relay and counter are used to
enable the circuit to operate two times. The designed used AC motor 240 V and
counter with 9 V voltage supply. This device probably will harmed the circuit if
lightning current flow through main supply [12].
The designed that are used before used counter that will count two times the
number of tripping. Relay are used as switch for circuit which in normal condition,
the relay will prevent the supply connected to the circuit completely. In tripping
condition, transistor will received the signal from counter to operate the motor and
switch on the ELCB [9-12].
23
CHAPTER III
METHODOLOGY
3.1 RC Servo motor [26]
Radio Control (RC) servo motor are a small actuators that designed for
remotely operating model vehicle like cars and airplanes. Nowadays, RC servo
motors are very popular with robotic design because of its ability to rotate and
maintain at certain position, location or angle. These movements can be control by
pulses from only a single wire. Inside this small box of RC servo motor contain of
small motor, gearbox, a potentiometer and electronic circuit. A potentiometer is used
to measure the position of output gear, while the electronic circuit control the motor
to the desired position with specific gear change.
Servo motors have three wires that connect to power wire (V+), ground wire
(V-), ad signal wire (S). The power wire is in red colour typically and connected to
the supply 5 volts. The ground wire is in brown colour and connected to the ground
point at the circuit. The signal wire is in orange colour and connected to the signal
pin at microcontroller PIC. The signal wire will received Pulse Width Modulation
(PWM) signal from external controller circuit.
24
Figure 3.1: Servo Motor
The servo controller is the external electronic device that control RC Servo
by generates and sending pulse width modulation signal (PWM). The electronic part
inside the servo will translate this PWM signal into position values and instructed the
servo to move. The PWM signal was converted to electrical resistance value and
powered on the DC motor. The rotation of motor also makes the potentiometer to
rotate and produce the electrical resistance. This electrical resistance value then sent
back to the servo electronic until the potentiometer value matches the position value
translated from PWM signal.
(a)
(b)
Figure 3.2: (a) Servo Component (b) Servo Internal Part
25
The “neutral” position of the servo is the position when pulse width signal
(PWM) of approximately 1.5 ms (1500 µs). Neutral is defined as a point when the
amount of potential rotation of counter clockwise and amount of potential of
clockwise are exactly the same. The servo moves some number of degrees counter
clockwise from the neutral when the pulse signal (PWM) sent to servo is less than
1.5 ms. The servo also moves some number of degree clockwise from the neutral
point when the pulse is greater than 1.5 ms. For servo motor the maximum pulse
input will be 2.0 ms, the minimum pulse input will be 1.0 ms and the stop movement
(neutral) at 1.5 ms.
Figure 3.3: PWM Waveform
26
3.1.1 Servo Power
Servo power is a term that defined as the amount of DC voltage needed to
operate a servo without damage. RC servo motor commonly run on 5 volts DC but
they often work with voltages between 4.5 – 6.0 volts with the current range from
200 mA to 1 Amp. Servo motor tends to be faster and stronger at higher voltage but
can heat up faster when stalled or in a hold position with stress forces against the
servo output shaft.
3.1.2 Servo Speed
Servo speed is a term that defined as the amount of time ( in seconds ) that a
servo arm attached to the servo output shaft will move from 0 to 60 degrees. The
lower the time (seconds) the faster the servo can move an attached wheel or arm. For
example a servo rated at 0.20 seconds/ 60 degrees takes 0.20 seconds to sweep
through a 60 degrees arc. But the faster the servo may results in lower of torque
available.
Figure 3.4: Servo Speed
27
3.1.3 Servo Torque
Servo torque is a term that defined as ounce-inch (or oz-in) force in ounces
times inches. It is the total push or pulls power a servo can apply on one servo arm
when moving. Servo torque is measured by the amount of weight (in ounces) that a
servo can hold at 1-inch out on the servo output arm in the horizontal plane.
Figure 3.5: Servo Torque
3.1.4 Servo Wire Connection
There are three connections for RC servo motor, VCC, grounding and signal.
The colour for each wire is different depends on their type.
28
Figure 3.6: Servo Connection
Figure 3.7: Servo Wire Code
29
3.2 Device Components
There are several components that used as a driver for automatic reclose
Earth Leakage Circuit Breaker (ELCB). The components choose for these projects
are:
a)
RS Servo Motor C36R
b)
PIC Microcontroller 18F4550
c)
Voltage Regulator 7805
d)
Crystal
e)
Basic switch
f)
Resistor
g)
capacitor
h)
Battery 12 V
3.2.1 PIC Microcontroller 18F4550 [23-24]
Nowadays, almost all modern devices used embedded microcontroller that
can be programmed to perform any number of task. There are many types of
application that used the number of different types of microcontroller. The easiest
and the most popular microcontroller used for such task oriented applications are the
8-bit PIC 18F4550 microcontroller from Microchip. The PIC 18 family of MCUs
(Microcontroller Unit) with a maximum clock speed of 40 MHz and 128 Kb of Flash
memories are some of the fastest and most feature loaded 8-bit PIC on the market.
30
Figure 3.8: PIC
These PIC are small enough for embedded application but powerful enough
to allow a lot of freedom and complexity in design process. The centralized interface
between the programmer and the device is allowed by using MPLAB Integrated
Development Environment (MPLAB IDE). For low cost real time debugging of all
PIC, the MPLAB ICD 2 In-Circuit is the most powerful and cost efficient tools.
Figure 3.9: Interface using MPLAB IDE
31
One of the typical PIC 18F4550 feature-loaded is every I/O pin are connected
to an internal peripheral device. The other feature including 8 and 16 bit timer
modules
with
various feature,
master synchronous
serial
port
modules,
capture/compare/PWM module, 10 bits analogue to digital converter, universal
synchronous receiver and transmitter and many more. Interestingly, all of these
feature can be turn on and off in the program code.
Figure 3.10: PIC 18F4550
Some special feature include 100,000 erase/write cycle Enhanced Flash
program memory typical, 1,000,000 erase/write cycle data EEPROM memory typical
and the Flash/Data EEPROM Retention can last for more than 40 years. One of the
application that used PIC 18F4550 is to control the servo motor. With a simple
programming using MPLAB IDE, the servo motor can easily control to move at
desired position.
32
3.2.2 Voltage Regulator LM7805 [19]
Voltage regulator is one of the DC-DC Converter that converts the DC
voltage of input supply into the desired DC voltage. It usually has three legs and
converts the varying input voltage and produces a constant regulated output voltage.
The family of 78XX voltage regulators are designed for positive input.
Figure 3.11 Voltage Regulators LM7805
The LM7805 can hold current up to 1 Amp and the input leg can hold the
voltage up to 36 VDC. The capacitor is recommended to put parallel between an
output leg and common leg for maximum voltage regulation. Basically, 0.1mF was
used to eliminate any high frequency AC voltage that will combine with output
voltage. For LM7805 voltage regulator, the output voltage should be 5 VDC.
Figure 3.12: Voltage Regulator Schematic diagram
33
3.2.3 Crystal Oscillator [20,22]
Crystal oscillator is the combination of Micro Controller Unit (MCU) internal
circuitry for the needed in microcontroller clock frequency. Crystal oscillator is used
to provide a separate clock source that is compliant with both USB low speed and
full speed specification. This is due to the unique requirement from USB module to
produce a stable clock source.
Figure 3.13: Schematic Diagram
Figure 3.14: Typical Capacitor Value
34
3.3 Hardware Development
Literature
Review
Methodology
Proposal
Design
Implementation
& Testing
Discussion &
Conclusion
END
Figure 3.15: Flow chart of the overall project implementation
35
CHAPTER IV
CIRCUIT OPERATION & RESULT
4.1 Introduction
The aim of this project is to build a driver to pull up the ELCB switch
automatically without using human help. To achieve that, servo motor was used as a
mechanical power to pull up the ELCB switch. Servo motor was controlled by PIC
microcontroller that will send a signal to servo motor based on programming fixed.
The shaft of servo motor will rotate and pull up the ELCB switch and return back the
supply.
Micro controller PIC 18F4550 is the device that control the entire operation
of the circuit. The sensor will detect the condition of ELCB whether it is trip or not
and send signal to the PIC. PIC will afterwards send PWM signal to servo motor and
make it rotate based on the ELCB condition
36
4.2 Project Flow
DC VOLTAGE SUPPLY 5V
PIC 18F4550
SENSOR 1
SERVO MOTOR
SENSOR 2
ELCB
Figure 4.1: Circuit Operation Block Diagram
37
4.3 Circuit Design
Figure 4.2: Circuit Design
ISIS POFESSIONAL is software that used to design the circuit. There are
four main components that used in the design. There are servo motor, micro
controller PIC 18F4550, sensor and crystal oscillator. The entire component
characteristic had been discussed in the previous chapter. The type of sensor that are
used in this project are basic switch that function to give a signal to Micro controller
PIC based on the condition of ELCB.
38
4.4 Micro controller PIC 18F4550 Operation
As mention before, PIC 18F4550 is the brain of the device hat control the
entire operation. PIC was function when a certain programming was debugging into
the PIC chip. The programming using the C language contains the instruction for the
operation of servo motor. The programming can be done by using MPLAB IDE
software.
4.4.1 PIC Programming
This is the programming language or instruction to the servo motor to
operate.
//==========================================================================
//
include
//==========================================================================
#include <p18f4520.h>
// this sample code is using 18F4520 !!
#include "delays.h"
#include "usart.h"
//
configuration
//==========================================================================
#pragma config OSC = HS
// HS oscillator
#pragma config FCMEN = OFF
// Fail-Safe Clock Monitor disabled
#pragma config IESO = OFF
// Oscillator Switchover mode disabled
#pragma config PWRT = OFF
// PWRT disabled
#pragma config BOREN = OFF
// Brown-out Reset disabled in hardware
and software
#pragma config WDT = OFF
// WDT disabled (control is placed on the SWDTEN
bit)
#pragma config MCLRE = ON
// MCLR pin enabled; RE3 input pin
disabled
#pragma config PBADEN = OFF
digital I/O on Reset
// PORTB<4:0> pins are configured as
39
#pragma config CCP2MX = PORTC
// CCP2 input/output is multiplexed with RC1
#pragma config LVP = OFF
// Single-Supply ICSP disabled
#pragma config XINST = OFF
//
// Extended Instruction Set
define
//==========================================================================
#define servo
LATBbits.LATB1
#define sw1
PORTBbits.RB6
#define sw2
PORTBbits.RB7
#define MHZ
*1000L
#define KHZ
*1
#define DelayUs(x)
/* number of kHz in a MHz */
/* number of kHz in a kHz */
{ unsigned char _dcnt; \
_dcnt = (((x)*(20MHZ))/(24MHZ))|1; \
while(--_dcnt != 0) \
continue; \
_dcnt = (((x)* (20MHZ))/(24MHZ))|1; \
while(--_dcnt != 0) \
continue; }
//===========================Sub
function====================================================
void delay(unsigned long data)
//delay function, the delay time
{
//depend on
the given value
for( ;data>0;data-=1);
}
void DelayMs(unsigned char y)
{
unsigned char
i;
do {
i = 4;
do {
DelayUs(250);
} while(--i);
} while(--y);
}
//============================main
function=============================================
void main(void)
{
unsigned int loop;
40
TRISB = 0b11000000;
//servo motor is RB1
PORTB = 0b00000000;
//clear port B
if(sw1==1)
{
for(loop=0;loop<50;loop++)
{
servo=1;
DelayMs(3);
DelayUs(250);
DelayUs(250);
DelayUs(250);
servo=0;
DelayMs(16);
DelayUs(250);
}
}
// _
_
_
// | |
||
||
// | |
||
||
// | |_________________| |________________| |____________________
// 0.7ms
19ms
0.7ms
// |
// |<-------20ms------>|
else if(sw2==1)
{
for(loop=0;loop<50;loop++)
{
servo=1;
DelayUs(100);
servo=0;
DelayMs(19);
DelayUs(250);
DelayUs(250);
DelayUs(250);
DelayUs(150);
}
}
19ms
0.7ms 19ms
|
41
else
{
servo=0;
}
}
4.4.2 Pulse Width Modulation
Pulse Width Modulation is the signal waveform which PIC sent to servo
motor as the instructor for servo motor to move. PIC will generate this square
waveform from the programming that already set into it. The controller circuit in the
servo motor will read this waveform and translate it in term of the motion by motor
and gearbox. Servo motor that used in this project is the type that can rotate 180º.
This waveform will determine the rotation of servo motor shaft. To pull up
the ELCB switch, the motor shaft needs to rotate counter clockwise 180º. The pulse
length needs to set at 0.1 ms to make the motor shaft rotate counter clockwise. Then,
the motor shaft need to turn back to its initial position. Therefore the motor shaft
needs to rotate 180º clockwise. The pulse length needs to set at 1.25 ms so that motor
shaft will rotate clockwise.
42
Figure 4.3: PWM Input Signal
4.5 Circuit Operation
At normal condition, servo was set at standby mode. There are two sensors
that were putted at ELCB switch. Sensor 1 was put at the bottom of the ELCB switch
and sensor 2 at the top.
These sensors were in the type of basic switch that
connected to the PIC. When tripping occurred due to short circuit, sensor 1 will
detect the tripping.
When tripping occurred, ELCB switch will push the sensor 1 and send the
signal to the microcontroller PIC 18F4550.PIC will generate PWM signal waveform
and send the signal to the servo motor. The controller circuit in the servo motor will
read the PWM signal and translate it in the form of motor movement.
43
The movement of the motor make the gearbox, feedback potentiometer and
motor drive shaft also move. Feedback potentiometer was function to give a
resistance to the motor. The resistance of feedback potentiometer is corresponding to
the angle that had been set from translated PWM waveform signal. The motor shaft
will rotate counter clockwise 180º and at the same time pulled up the ELCB switch.
When the rotation had reach 180º, the feedback potentiometer will give a resistance
and stop the motor movement.
When the ELCB switch had fully pulled up, the ELCB will on and return
back the power supply. Sensor 2 will detect it and send the signal to the PIC. PIC
will generate PWM signal waveform and send the signal to servo motor. The
controller circuit will read the signal and translate it in the form of motor movement.
The motor shaft will rotate clockwise 180º at return back to its initial position. This
is to make sure if the tripping occurred again, the servo shaft will not prevent the
ELCB to trip.
ELCB TRIP
When the ELCB
switch had fully
on, sensor 2 will
detect it and
send signal to
PIC
PIC will
generates PWM
impulse signal to
the servo motor.
Sensor 1 detect
the tripping and
send signal to
PIC
The rotation will
be 180º and
pulled up the
ELCB switch
Servo motor
received the
signal and rotate
counterclockwise
PIC will
generates PWM
impulse signal to
the servo motor
Servo motor
received the
signal and rotate
counterclockwise
The rotation will
be 180º and
back to its
initial position.
Figure 4.4: Operation Flow
44
4.6 Result
Figure 4.5: Hardware Device
The hardware was successfully develop and functioning well to pull up the
ELCB switch. If the tripping occurred and the ELCB switch is pulled up once and
return back the power supply, assumption can be made that the fault occurred is
temporary type. The fault maybe due to the lightning.
If the tripping occurred and the ELCB switch is pulled up but tripping
occurred again, the motor will stop its movement. This is because the PIC was set to
stop the motor if sensor 2 was push twice. An assumption can be made that the
permanent fault type had been occurred.
45
4.7 Discussion
The automatic reclose device was successfully performing their duty to pull
up the ELCB switch but there are still some problem that need to be considered. One
of the problems encountered in this project is about the PIC programming itself. The
programming was set to perform the motor movement and rotate to the desired
position. But the motor only moves for the next action after the reset button was
push. That‟s mean the operation was not continuous. Therefore some changing need
to be done to the programming so that the motor can perform a continuous action
without pushing the reset button.
In this project, the motor was set to stop their operation if the tripping occurs
two times subsequently. That incident happened maybe due to short circuit current.
But we need to considered if the lightning occurred two times or more that make the
ELCB trip twice and the motor stop their operation because of it mistaken it with
permanent fault current.
46
CHAPTER V
CONCLUSION & RECOMMENDATION
5.1 Conclusion
ELCB is one of the protective devices that will isolate the load from
electrical supply if fault current occurred. ELCB was widely used and can operate
efficiently and effectively. Nevertheless, there is no mechanism to turn on the ELCB
automatically for home appliance.
Therefore, this research was conducted to study and understanding the
operation and mechanism of automatic reclose device with Earth Leakage Circuit
Breaker. The function of auto reclose device is to pull up the ELCB switch after
tripping and return back the power supply. Then, the device was successfully design
and develop and functioning well to pull up the ELCB switch.
47
5.2 Recommendation
The automatic reclose device was functioning well to pull up the ELCB
switch but there are some feature that should be added to make it perfect Therefore
further research need to be conducted to create a design that can be commercialize
for house appliance. These are some recommendation that should be consider for
future work.
Firstly, the servo motor needs to change to the type that can rotate 360º. In
this project, the servo motor used only can rotate 180º. Thus two sensors are needed
to make the servo rotate to pull up the ELCB switch and return back to its initial
position. By using 360 º rotation servos, only one sensor is needed.
In this project, power supply for servo motor and PIC driver comes from
adapter. In commercial design, we need to use the rechargeable battery as a power
source. We also need to put the converter to recharge the battery from the ac input
source. This to make sure the continuous input source for the driver.
The most important things are to make the smaller and cheaper driver.
Smaller are the important aspect in commercial design because it easier for the user
to buy it from electrical shop. Cheaper also important because user prefer the
electrical device that high in quality and low price.
Lastly, the design should be creative and small enough so that user will just
buy it and put it at the ELCB like plug and play. This is more convenient for home
appliance and definitely highly safety.
48
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Viv Cohen, Why Electronic and Not Electromechanical ELCB’s, IEEE
Journals, 1996.
2.
Tom Harris, How Circuit Breaker Work,
electronic.homestuffworks.com/circuit_breaker.htm
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Earth Leakage Circuit Breaker, catalog, www.peopleelectric.cn/AB
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Mohd Azrie Bin Suarin, Automatic Tester Device for Earth Leakage Circuit
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49
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Voltage Regulator,
http://www.eidusa.com/Electronics_Voltage_Regulator.htm
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Shenzhen Jinghua Crystal Electronic, Crystal Oscillator,
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Microchip Technology Inc. (2007), PIC 18F2455/2550/4455/4550 Data
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Michael Aeberhard, 8-Bit PIC 18 Microcontroller Units, A Technology
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Bradley E. Bishop, Jenelle Armstrong Piepmeier, George Piper, Kenneth A.
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26
Blue Point Engineering (2007), Servomotor Information, pdf.
51
APPENDIX A
64
APPENDIX B
70
APPENDIX C