OVER/UNDER VOLTAGE PROTECTOR

NAH KIEN WAH

THIS DISSERTATION IS SUBMITTED IN PARTIAL FULFILMENT OF THE BACHELOR DEGREE IN SCIENCE WITH HONOURS

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PHYSICS WITH ELECTRONIC PROGRAMME SCHOOL OF SCIENCE AND TECNOLOGY

UNIVERSITI MALAYSIA SABAH

April 2008

UNIVERSITI MALAVSIA SABAH

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mengaku membenarkan tesis (LPSM/Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Universiti Malaysia Sabah dengan syarat-syarat kegunaan seperti berikut: -

1. Tesis adalah hakmilik Universiti Malaysia Sabah. 2. Perpustakaan Universiti Malaysia Sabah dibenarkan membuat salinan untuk tujuan pengajian

sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institutsi

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CATATAN: - "Potong yang tidak berkenaan. ""Jika tesis ini SULZT atau TERHAD, sila lampirkan surat daripada pihak berkuasa

/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT dan TERHAD.

@Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan atau disertai bagi pengajian secara kerja kursus dan Laporan Projck Sarjana Muda (LPSM).

--..... 1 1 9.31n ahtstin (Mengandungi maklumat yang berdarjah keselamatan atau Kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

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DECLARATION

I verify that this project is my own work except some materials are taken from the

work of others, in which each case has been indicate its source.

5th Mei 2008

NAH KIEN WAH

HS2005-2652

APPROVAL OF EXAMINERS

APPROVED BY

Signature

1. SUPERVISOR

(Ms. Teh Mee Tenb)

2. EXAMINER I

(Associate Prof. Dr. Jedol Dayou)

3. EXAMINER 2

(Mr. Saafie Salleh)

4. DEAN

(Associate Prof. Dr. Shariff A. Kadir Omang)

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111

ACKNOWLEDGEMENT

I wish to express my appreciation to my supervisor, Ms Teh Mee Teng for her

motivation in leading me and other undergraduates in their final year project. She has

provided us with her knowledge and guides generously from time to time. I hereby

take this opportunity to express my gratitude for her continuous guidance and advices

throughout this project.

I would also like to extend my heartiest gratitude to all the lecturers in my

course for all their ideas and inspiration. Special appreciation also express to William

Ker and En. Rahim who willing to assist in provided all necessary instrument and

equipment to make the circuit success.

Finally, let me say thanks to my family members for their moral and finance

support.

ABSTRACT

Over/under voltage protector is designed particularly to overcome the over voltage

and under voltage events. It is sensitive enough to disconnect the power supply when

the input voltage is out of specific range. Various "over voltage" and "under voltage"

is created by using several steps down transformers. Secondary windings of

transformers are connected serially, and then its combination voltage measured will be

the sum of the output of each transformer. The circuit constructed is connected by the

voltage supply which is higher than household power supply (over voltage), hence

over voltage range can be determined. While the under voltage range is determined by

connecting the voltage supply which is lower than household power supply (under

voltage), to the circuit. Operational amplifier IC in the circuit compare its DC voltage

with corresponding zener diode, hence control the range of normal power supply

permitted in the over/under voltage protector. Over/under voltage protector is built

and its range of "voltage permitted" is set to 183.36 V to 262.00 V with uncertainty of

4.61% for over voltage edge and 1.86% for under voltage edge. However, the range of

the over voltage and under voltage still can be adjusted using variable resistor VRI

and VR2 respectively.

V

ABSTRAK

Pelindung voltan tinggi/rendah direka cipta untuk menangani masalah "voltan tinggi"

dan "voltan rendah". Alat ini adalah sensitif untuk memutuskan berkalan elektrik

daripada peralatan elektrikal, apabila berkalan voltan melebihi atau kurang daripada

julat yang ditentukan. Beberapa set "voltan tinggi" dan "voltan rendah" dicipta dengan

menggunakan beberapa transformer perendah. Output transformer disambung secara

seri, seterusnya voltan gabuangan yang didapati merupakan jumlah setiap output

transformer. Litar disambung kepada beberapa "voltan tinggi" yang lebih tinggi

daripada voltan perumahan, untuk menentukan had maksimum voltan tinggi yang

dibenarkan oleh pelindung voltan tinggi. Begitu juga dengan had minimum voltan

rendah, beberapa "voltan rendah" yang rendah daripada voltan perumahan disambung

kepada litar. Op-Amp IC dalam litar memainkan peranan dalam membandingkan

voltan DC yang melaluinya, seterusnya mengawal julat voltan biasa yang dibenarkan

oleh pelindung voltan tinggi/rendah. Pelindung voltan tinggi/rendah dibina dan julat

voltan yang dibenarkan ditentukan pada 183.36 V dan 262.00 V, dengan

ketidakpastian 4.61 % untuk sempadan voltan tinggi dan 1.86 % untuk sempadan

voltan rendah. Bagaimanapun, julat antara sempadan voltan tinggi dan voltan rendah

boleh diselaraskan dengan mengunakkan perintang pembolehubah, VRI dan VR2

masing-masing.

V1

CONTENTS

DECLARATION

APPROVAL

ACKNOWLEDGEMENT

ABSTRAC

ABSTRAK

LIST OF CONTENT

LIST OF TABLES

LIST OF FIGURES

LIST OF PHOTOS

LIST OF SYMBOLS

CHAPTER 1 INTRODUCTION

1.1 Background

1.2 Purpose of Project

1.3 Objective of Project

1.4 Scope of Project

1.5 Hypothesis

CHAPTER 2 LITERATURE REVIEW

2.1 Electrical Transmission and Distribution

2.1.1 Grounding System

2.1.2 Electrical Meter

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2.1.2. a Electromechanical Meter

2.1.2. b Electronic Meter

2.2 Safety Device

2.2.1 Fuse

2.2.2 Circuit Breaker

2.2.3 Surge Protector

2.2.4 Gas Discharge Arrestor

2.3 Overvoltage Protector

2.3.1 Crowbar Circuit

2.3.2 Series Connected Switch Circuit

2.4 Conversion from AC to DC

2.4.1 Half Wave Rectifier

2.4.2 Full Wave Rectifier

CHAPTER 3 METHODOLOGY

3.1 Introduction

3.2 Material and Instrument

3.2.1 Soldering Iron

3.2.2 Lead Solder

3.2.3 Soldering Sucker

3.2.4 Digital Multimeter

3.2.5 Transformer

3.2.6 Relay

3.2.7 Variable Resistor

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3.2.8 Op-amp LM324

3.2.9 Regulator IC 7812

3.3 Construction of Circuit

3.3.1 Schematic Circuit Diagram

3.3.1. a Original Circuit

3.3.1. b Modify Circuit

3.3.2 Procedures of Circuit's Construction

3.4 Protection Experiment

3.4.1 Over Voltage

3.4.1. a Formation of Over Voltage

3.4.1. b Measurement of Secondary Voltage

with "Over Voltage" Input 3.4.1. c Determination of Over Voltage

Range

3.4.2 Under Voltage

3.4.2. a Formation of Under Voltage

3.4.2. b Measurement of Secondary Voltage

with "Under Voltage" Input

3.4.2. c Determination of Under Voltage

Range

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CHAPTER 4 RESULTS AND DISCUSSION

4.1 Introduction

4.2 Formation of Testing Voltage

4.3 Measurement of Secondary Voltage of Main

Transformer with Primary Testing Voltage

4.4 Determination of Over/Under Voltage Range

4.41 Over Voltage

4.42 Under Voltage

CHAPTER 5 CONCLUSION

5.1 Conclusion

5.2 Future Research

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REFERENCE 65

X

LIST OF TABLES

Table No.

2.1 Sizes of tinned copper wire fuse elements

3.1 Formation of "Over Voltage"

3.2 Secondary Voltage of Main Transformer with

"Over Voltage" Input

3.3 DC Voltage of Pin 3 with Respond of Relay

3.4 Formation of "Under Voltage"

3.5 Secondary Voltage of Main Transformer with

"Under Voltage" Input

3.6 DC Voltage of Pin 6 with Respond of Relay

4.1 Formation of "Over Voltage"

4.2 Formation of "Under Voltage"

4.3 Deviation between Theoretical and Actual

Reading

4.4 Secondary Voltage of Main Transformer with "Over Voltage" Input

4.5 Secondary Voltage of Main Transformer with "Under Voltage" Input

4.6 Turns ratio of Main Transformer

4.7 Voltage at Pin 3 and Respond of Relay at 6.5 k S2

4.8 Voltage at Pin 3 and Respond of Relay at 3.8 k 12

4.9 Voltage at Pin 6 and Respond of Relay at 4.3 k C)

4.10 Voltage at Pin 6 and Respond of Relay at 2.6 k S2

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LIST OF FIGURES

Figure No.

2.1 Electrical Power Transmissions and Distribution

2.2 Wiring Orientation of Transformer to Household

Power Supply

2.3 Single Stator Electromechanical Meter

2.4 Fuse

2.5 Circuit Breaker

2.6 Internal Design and Structure of Circuit Breaker

2.7 Surge Protector

2.8 Simple MOV Surge Protector with Line

Conditioning and a Fuse

2.9 Gas Discharge Arrestor

2.10 Crowbar Circuit

2.11 Series Protector for Over/Under Voltage

2.12 Basic Circuit for Half Wave Rectifier

2.13 Input and Output Voltage Waveforms for the Half

Wave Circuit

2.14 Basic Circuit for Full Wave Rectifier

2.15 Input and Output Voltage Waveforms for the Full

Wave Circuit

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3.1 SPDT Relay

3.2 Pin Connection Diagram of LM 324

3.3 Voltage Regulator 7812

3.4 Original Circuit without Op-amp IC and Transistor

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3.5 Schematic Diagram of Modify Circuit 37

X111

LIST OF PHOTOS

Photo No.

3.1 Soldering Iron with Stand

3.2 Lead Solder

3.3 Sucker

3.4 PeakTech®3140 Digital Multimeter

3.5 Transformer

3.6 Preset

3.7 Op-amp LM324

3.8 Modified Circuit on Strip Board

4.1 Formation of Testing Voltage

4.2 Over/under voltage protector under normal power

supply (183.36 V- 262.00 V)

4.3 Over/under voltage protector out of normal voltage

range (less than 183.36 V or more than 262.00 V)

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fIr

Hz

w

A

V W

S2

TTL

MOSFET

rms

LIST OF SYMBLOS

operating frequency

Hertz

angular Velocity

ampere

volt

watt

ohm

transistor-transistor logic

metal oxide semiconductor field transistor

root mean sq

CHAPTER 1

INTRODUCTION

1.1 Background

Electronic components have been designed to function properly when used within

their specified current and voltage ratings. When these ratings are exceeded during

operation, or known as over voltage, the component may sustain permanent damage

and the equipment may cease to operate. The conditions may be hazardous.

Depending on its duration, the over voltage events can be permanent or transient, the

latter case also being known as a voltage spike.

A more common scene of over voltage or over current is the operation of high-

power electrical devices such as air conditioners and refrigerators. These high-

powered pieces of equipment require a lot of energy to switch on and turn off

components like compressors and motors. This switching creates sudden, brief

demands for power, which upset the steady voltage flow in the electrical system.

While these surges are much less than the intensity of a lightning surge, they can be

severe enough to damage components, immediately or gradually, and they occur

regularly in most building's electrical systems.

1

I

2

Over voltage of power supply occur when something boosts the electrical

charge at some point in the power lines. This causes an increase in the electrical

potential energy, which can increase the current flowing to the wall outlet. When the

increase lasts three nanoseconds (billionths of a second) or more, it is called a surge.

While when it only lasts for one or two nanoseconds, it's called a spike. A number of

different things can cause this to happen.

The major source of the over voltage event are lightning strikes. When

lightning strikes near a power line, whether it's underground, in a building or running

along poles, the electrical energy can boost electrical pressure by millions of volts.

This causes an extremely large power surge that will overpower almost any over

voltage protector. In a lightning storm, sometime the best protection is to unplug their

electrical devices. However, these occurrences are always unexpected.

Other sources of over voltage are power outage, malfunction of electricity

supplier, and overload current that will cause the wire to melt, resulting short circuit

of electrical appliances.

In normal household and office wiring in our country, the standard voltage is

approximately 240 volts. If the voltage rises extremely beyond standard voltage, there

is a problem, and the over/under voltage protector helps to prevent that problem from

destroying our electrical appliances. Although under voltage condition is more rarely

to occur, and the occurrence does not bring any serious damage to the electrical

appliances, but once we know the faulty is caused by insufficient of voltage supply,

the proper maintenance and checking could be done shortly. Thus, unexpected

3

expense to repair and purchase new set could be avoided, given over/under voltage

protector is used.

1.2 Purpose of Project

The purpose of the project is to construct an over/under voltage protector to prevent

the electrical appliance from serious damage due to over or under voltage events.

1.3 Objective of Project

The objectives of the project are:

" To develop a circuit that could protect the electrical appliance against over or

under voltage events.

" To determine the exact range of normal voltage between over voltage edge

and under voltage edge, which is permitted by over/under voltage protector.

4

1.4 Scope of Project

The scope of the project is to build a circuit that responds to the transient voltage,

either exceeds 250 volts or less than 180 volts (approximately), the power supply will

disconnect immediately. The power supply will still connected to the appliance if the

voltage falls within 180 volts and 250 volts (approximately).

1.5 Hypothesis

The circuit developed is able to detect the over voltage and under voltage, hence

disconnect the power supply from the load.

CHAPTER 2

LITERATURE REVIEW

2.1 Electrical Transmission and Distribution

The electrical transmission system is the interconnection of the electric energy

produced by power plants with the loads. The operating frequency (fop) is 50 Hz in

our country. At the power station, an electrical generator converts mechanical power

into a set of alternating electric currents. The currents are sinusoidal functions of time,

all at the same frequency but offset in time to give different phases. In a three-phase

system, the phases are spaced equally, giving a phase separation of one-third cycle.

(Karady, G. G., 2006)

The three-phase power leaves the generator and enters a transmission

substation at the power plant. This substation uses large transformers to convert the

generator's voltage (which is at the thousands of volts level) up to extremely high

voltages for long-distance transmission on the transmission grid.

6

For power to be useful in a home or business, it comes off the transmission

grid and is stepped-down to the distribution grid. This may happen in several phases.

The place where the conversion from "transmission" to "distribution" occurs is in a

power substation. A power substation typically does several things:

" It has transformers that step transmission voltages (in the tens or hundreds of

thousands of volts range) down to distribution voltages (typically less than 10,000

volts).

" It has a "bus" that can split the distribution power off in multiple directions.

" It often has circuit breakers and switches so that the substation can be

disconnected from the transmission grid or separate distribution lines can be

disconnected from the substation when necessary.

After that, the power goes from the transformer to the distribution bus. The

bus distributes power to two separate sets of distribution lines at two different

voltages. The smaller transformers attached to the bus are stepping the power down to

standard line voltage (usually 7,200 volts) for one set of lines, while power leaves in

the other direction at the higher voltage of the main transformer. The wires at the

higher voltage need to be stepped down again, which will often happen at another

substation or in small transformers somewhere down the line. (Gonen, T., 1994)

After numerous further conversions in the transmission and distribution

network the power is finally transformed to the transformer drum, which is attached to

the pole. It reduces the 7,200 volts down to the 240 volts that makes up normal

7

household electrical service. There are two wires running out of the transformer and

three wires running to the house.

Figure 2.1 Electrical Power Transmissions and Distribution (Karady, G. G., 2006)

The two from the transformer are insulated, and the third one is bare. The bare

wire is the ground wire. The two insulated wires each carry 120 volts, but they are

180 degrees out of phase so the difference between them is 240 volts. The transformer

is wired in this sort of configuration (www. howstuffwork. com):

8

7,200 volts

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120 volts

Figure 2.2 Wiring of Transformer to Household Power Supply (Gonen, T., 1994)

2.1.1 Grounding System

In electricity supply systems, a grounding system defines the electrical potential of the

conductors relative to that of the Earth's conductive surface. Grounding system has

implications for the safety and electromagnetic compatibility of the power supply.

The grounding wire is directly or indirectly connected to one or more earth

electrodes. These may be located locally, be far away in the suppliers network or in

many cases both. This grounding wire is usually but not always connected to the

neutral wire at some point and they may even share a cable for part of the system

under some conditions. The ground wire is also usually bonded to pipe work to keep it

at the same potential as the electrical ground during a fault. Water supply pipes often

used to be used as ground electrodes.

A power ground serves to provide a return path for fault currents and therefore

allows the fuse or breaker to disconnect the circuit. The power ground is also often

bonded to the house's incoming pipe work, and pipes and cables entering the

65

REFERENCE

Brown, M., 2001, Power Supply Cookbook, Second Edition, Newnes, Butterworth-

Heinemann.

Crowell, B., 1999, Electricity and Magnetism, Edition 2.0. Fullerton, California.

Departments of the Army, and the Air Force, February 1995, Electrical Power

Supply and Distribution, TM 5-811-1/AFJMAN 32-1080, Washington, DC.

Fergusan, B., 2002, OVER VOLTAGE PROTECTION ON AC ADAPTER LNPUT,

Microsemi, Integrated Products.

Gheorghe, A. V., 2006, Critical Infrastructures at Risk, Securing the European

Electric Power System, Springer, Netherlands.

Halliday D., Resnick R., Walker J., 2001, Fundamental of Physics: the Sixth

Edition, John Wiley & Sons Inc, New York.

Rajashekara, K., Sohail Anwar, Barkhordarian, V., Alex, Q. I-I., Power Electronic

Devices, 2002, CRC Press LLC.