ABSTRACT

This project is Design and construction of single phase fault detector. Phase fault Detector is a device for identifying a phase failure of mains supply or other generating utility sets. It employs microcontroller as the core of the system in other to check the imbalance in the network. This project is divided into five chapters, chapter one deals with the introduction which discuss about phase fault detectors action. Chapter two deals with the literature review which critically examine the existing literature on the subject under research. Chapter three based on methodologies which discuss components description and analysis. Chapter four deals with the main project which treats the working principle of phase fault detector in power transformer. Finally chapter five is summary recommendation and reference.

CHAPTER ONE

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1.0 INTRODUCTION

Phase fault detector is a circuit that alerts by sounding an

alarm in event of power failure most of power supply

detector circuit need a separate power supply for

themselves, but in this project we present here needs no

additional power supply source. It employs an electrolytic

capacitor to store adequate charge to the circuit which

sound an alarm for a reasonable duration when the mains

supply fail.

Power transformer is a device that transfers electrical

energy from one circuit to another through intensively

coupled conductor. Phase fault detector is a device for

identifying mains failure in power transformer.

A fault in transformer is defined as a defect in the electrical

circuit due to which current diverted from the intended path.

The nature of fault implies any abnormal condition which

causes a reduction in the basic insulation strength between

phase conductors or between phase conductors and earth.

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During the presence of mains power supply, the

rectified mains voltage is stepped down to a required low

level via diodes (D1-D4). We used zener diode (D5) to limit the

filtered voltage to 15-vot level. Mains power presence in

indicator by a red LED. We used low level D.C for charging

capacitor (c3) and reverse of mains supply, the base of

transistor (T1). Since in the absent of mains the base of

transistor is pulled low via resistor (R8), it conduct and sound

the buzzer (alarm) to give a warning of the phase failure.

The aim of this project is to design and construct a

circuit that would give signal by sounding an alarm in an

occurrence of phase fault in transformer.

CHAPTER TWO

1.0 LITERATURE REVIEW

The objective of this chapter is to critically examine the

existing literature on the subject under research.

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The method of symmetrical components by J.B Gupta

power system 10Th Edition 2007-2008 Reprint, part iii page

66-105 [1] state that, any unbalanced three phase system of

currents, voltage or other sinusoidal quantities can be

resolved into three balance system of phases which are

called symmetrical components of the original unbalanced

system. Such three balanced systems constitute three

sequences network which are solved separately on a single

phase basis.

According to Mercedes [2] Short-circuit calculation used to

select the proper or short-circuit capacity of flow and

medium fault current circuit breaker and fuses.

These faults may either be three phase in nature involving

all three phase in a symmetrical (balanced) manner.

This type of fault occur infrequently, as for maintenance

and/or repair by damping all the three phase to earth, is

accidentally made alive or when due to slow fault clearance,

an earth fault spreads across to the other two phase or when

a mechanical excavator cut quickly through a whole cable.

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In a lecture presented by professor J. Rohan lucas in October

2005 [3], he said that fault analysis of a power system is

required in order to provide information for the selection of

switchgears, setting of relay and stability of system

operation. He further said that fault usually occur in a power

system line to either insulation failure, flash over, physical

damage or human error.

In a write up by Ashfaq Hessian [4], the purpose of fault

analysis is to determine the value of voltage and current at

different points of the system during the fault. Faults give

rise to abnormal operating condition, usually excessive

voltage and current at certain point on the system. Large

voltage stresses insulation beyond the breakdown value

while large current result in over heating of power system

components.

Furthermore, in a lecture presented in October 2004 by

Massimo mitolo, PHD, chu and Gassman consulting Engineer

[5], said that all electrical systems are susceptible to short

circuits and the abnormal current level they create. These

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current can produce considerable thermal and mechanical

stresses in a electrical distribution equipment. Therefore, it

is important to protect personal and equipment by

calculating short circuit current during system up grade and

design. Therefore equipment intended to interrupt current of

fault levels shall have an interrupting rating sufficient for the

nominal circuit voltage and the current that is available at

the line terminals of the equipments. More, so fault analysis

is required to calculate and compare symmetrical and

unsymmetrical current values in order to select a protective

device to adequately protect piece of electrical distribution

equipments.

CHAPTER THREE

3.0 COMPONENTS DESCRIPTION

3.1 DIODES: Diodes allows Electricity to flow in one

direction .The arrows of circuit symbol shows the description

in which the current can flow.

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K01a

Fig3.1 Diode symbol A typical Diode

1. Forward voltage Drop: Electricity uses up a little

energy pushing up its way through the diode. This means

that there is a small voltage across a conducting diode, it

is called the forward voltage drops and is about 0.7v for

all diodes which are made from silicon. The forward

voltage drop of a diode is almost constant no matter the

current passing through the diode, so they have a very

step characteristic.

2. Reverse Voltage: When a reverse voltage is applied, a

perfect diode does not conduct, but all real diodes leak a

very tiny current of a few micro ampere. This can be

ignored in most circuit because it will be very much

smaller than the current flowing in the forward direction.

However all diodes have a maximum reverse voltage and

(usually 50v or more) if this exceeded, the diode will fail

and pass a large current in the reverse direction, this is

called BREAK DOWN.

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Connecting and soldering: diodes must be connected the

correct way round. It labeled, a for anode and K for cathode.

The cathode is marked by a line painted on the body. Diodes

are labeled with their code in small print, rectifier diodes are

quite robust and no special precautions are needed for

soldering them. Diodes can be test by using a multi meter or

simple tester (battery, resister and LED) to check that a

diode conduct in one direction.

3.2 ZENER DIODES: It is a reverse-biased heavily- doped

silicon (or germanium) P-N junction diode which is operating

in the breakdown region where current is limited by both

external resistance and power dissipation of the diode.

Anode ∫ cathode

Fig 3.2 Zener Diodes Symbol.

Zener diode are used to maintain a fixed voltage, they are

designed to breakdown in a reliable and non-destructive way

so that they can be used in reverse to maintain a fixed

voltage across their terminal. They connect with a resistor in

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series to limit the current. Zener diodes are rated by their

breakdown voltage and maximum power. The minimum

voltage available is 2.7v. Power ratings of 400mw and 1.3w

are common.

3.3 RESISTOR: it is an electronic device which has a

property called resistance, which opposes or reduce the flow

of electric current in a circuit. Resistor is measured in ohms

(Ω) A resistor cannot store electric energy. It can only

dissipate it in form of heat. The function of resistors are as

follow:

a) It provide a voltage drop

b) To limit the flow of current in a circuit

c) Dissipating electric energy.

Resistor can either be of fixed or variable. The fixed resistors

have a constant resistance while the variable resistor, their

resistance is not fixed but varies. An increase in resistance

brings about a decrease in voltage but lower current while

decrease in resistance brings about increase in voltage and

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increase in current. Below is the and symbol of both fixed

and variable resistor.

Fig 3.3 Symbol of fixed and variable Resistors

Resistor values are normally shown using colored bands.

Most resistors have four bands. The first band gives the first

digit. The second band gives the second digit. The third

bands indicate the number of zeros. The fourth band is used

to show the tolerance of the resistor, this may be ignored for

almost all circuits. The tolerance is the percentage by which

the resistance of the resistor may be higher or lower than

the cored value. Below is the typical resistor colour code

table

Colour number multiplier tolerance

Black 0 1 -

Brown 1 10 -

Red 2 102 ±2%

Orange 3 103 -

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Yellow 4 104 -

Green 5 105 -

Blue 6 106 -

Violet 7 107 -

Gray 8 108 -

White 9 109 -

Silver 10 10-2 ±10%

Gold 11 10-1 ±5%

Table 3.1

Electrical energy is converted to heat when current flow

through a resistor. Usually the effect is negligible, but if the

resistance in low or the voltage across the resistor is high, a

large current may pass making the resistor become

noticeable warm. The resistor must be able to withstand the

heating.

Power rating of resistor are rarely quoted in parts list

because for most of circuit, the standard power ratings of

0.25w or 0.5w are suitable for the rare cases where a

higher power is required. it should be clearly specified in

the parts list.

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3.4 CAPACITORS

Another important electronic component used in this project

is the capacitor. Capacitors store electric charge. They used

resistor in timing circuits because it taken time for a

capacitor to fill with charge. They are used to smooth

varying AC supplies by acting as a reservoir of charge. They

are also used in filter circuit because capacitor easily

pass AC charging signal but they block AC (constant)

signals. A capacitor essentially consists of two conducting

surface separated by a layer of an insulating medium called

the dielectric. The dielectric material may be air, electrolyte,

plastic or paper. The dielectric material is used to

determine the name of the type capacitor basically store

dielectric charges energy and block the flow of direct

current while passing alternating current.

Capacitance is a measure of a capacitors ability to store

charge. A large capacitance means that more charge

can be stored; capacitance is measured in farads, symbol (f).

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However, (IF) is very large so prefixed are used to show the

smaller values.

Three prefixes (Multipliers) are used µ (micro), n (nano) and

P(Pico). So capacitor values can be very difficult to find

because there are many types of capacitor with different

labeling system.

There are many types of capacitor but they can be split into

two groups polarized and unpolarized. Each group has its

own circuit symbol.

Fig 3.4 Electrolyte capacitors symbol

Electrolyte capacitors are polarized and they must be

connector the correct way round, at least one of their leads

will be marked + or -. They are not damaged by heat when

soldering. There are two designs of electrolyte capacitors.

Axial where the leads are attached to each end and radial

& where both leads are at the same end. Radial capacitors

tend to be a little smaller and they stand upright on the

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+-

circuit boards. It is easy to find the value of electrolyte

capacitors because they are clearly printed with their

capacitance and voltage rating.

However, order ones used a colour- code system which

has two stripes (for the two digits) and a spot of colour

for the number of zeros to give the value in µf. the

standard colour code is used, but for the spot, grey is

used to mean X 0.01 and white means X 0.1 so that values

of less than 1.0 µf can be show. A third colour stripe near

the leads show the voltage.

Unpolarized capacitors (small values, up to 1 µf)

Fig 3.5 unpolarized capacitor symbol.

Small value capacitors are unpolarized and may be

connected either way round. They are not damaged by heat

when soldering, except for one unusual type (Polystyrene).

They have high voltage rating of at least 50V, usually 250V

or so. It can be difficult to find the values of these small

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capacitors because there are many types of them and

several difficult labeling systems. A number code is often

used on small capacitors where printing is difficult.

3.5 (LED) LIGHT EMITTING DIODES

It is a forward biased P-N junction which emits visible light

when energized. The charge carrier recombination taken

place electrons from the N- side cross the junction and

recombine with the holes on the P-side.

LEDs emits light when an electric current passes through

them. LEDs operate at voltage level from 1.5v to 3.3v

Fig 3.6 light emitting diode symbol.

Connecting and soldering

LEDs must be connected the correct way round, the diagram

labeled a for anode and K for cathode. The cathode is the

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short lead and there may be a slight flat on the body of

round LEDs. If you can see inside the LED the cathode is

the larger electrode (but this is not an official

identifications methods ). LEDs can be damaged by heat

when soldering but the risk in small unless you are very

slow. No special precautions are needed for soldering most

LEDs.

Never connect an LED directly to a battery or power supply,

it will be destroyed almost instantly because too much

current will pass through and burn it out LEDs must have

a resistor in series to limit the current to safe value. For

quick testing purpose a 1KΩ resistors is suitable for the most

LEDs if supply voltage is 12v or less.

LED Clip

LEDs are available in a wide variety of sizes and shapes. The

standard LED has a round cross- section of sum-diameter

and this is probably the best type of general use but 3mm

round LEDs are also popular. LEDs clip are also available to

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secure LEDs in holes. Other cross-section shapes include

square, rectangular and triangular.

The uses of LEDs include the following.

1. LEDs are used in burglar alarm system.

2. In data links and remote controllers

3. In image sensing circuits used for picture phone.

4. For numeric displays in hand held or pocket calculators.

3.6 TRANSISTOR

The transistor is a small conductor device. They are made

from silicon or germanium but silicon type is better since

they operate at higher temperature. There are two types of

standard transistor, NPN and PNP, with different circuits

symbols. The letters refers to the layers of semi conductor

material used to make the transistor. Most transistors used

today are NPN because this is the easiest type to make from

silicon.

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b

e

c

NPN PNP

e

b

c

Fig 3.7 Diagram of a transistor

The leads are labeled based (b), collector (c) and Emitter (e).

these terms refers to the internal operations of a

transistor but they are not much help in understanding

how a transistor is used. The three leads must be

connected properly. Transistors amplify current, they can be

used to amplify the small output current from a logic clip,

so that it can operate a lamp, relay or other high current

device. In many circuit a resistor is used to convert the

charging current to a charging voltage , so the transistor

is being used to amplifying voltage.

Connecting and soldering

Transistors have three leads which must be connected in

correct way round. Care should be taking because a wrongly

connected transistor may be damaged instantly when the

circuit is switch on.

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Transistor can be damaged by heat when soldering. So if you

are not an expert it is wise to use a heat sink chipped to the

lead between the joint and the transistor body.

Choosing a transistor and testing.

Most project will specify a particular transistor but if

necessary, you can usually substitute and equivalent

transistor from the wide range available. The most

important properties to look for are the maximum

collector current (IC) and the current gain hfe. To make a

final choice, you will need to consult the tables to

technical data which are normally provided in catalogues

methods for testing an NPN transistor

1. Testing with a multimeter

2. Testing in a simple switching circuit

To test a PNP transistor use the same method but reverse

the leads and the supply voltage.

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3.7 PIEZO BUZZER

It is an output Transducer converting electrical energy to

sound. They contain an internal oscillator to produce the

sound which is set at 400HZ.

Fig 3.8 Piezo buzzer symbol

Buzzer have a voltage rating but it is only approximate

for example 6v and 12v. Buzzer can be used with a 9v

supply. Their typical current is about 25mA. They may be

connected either way round except in stereo circuits

when the + and – markings on their terminal must be

observed to ensure the two speaker are in phase. Correct

polarity must always be observed for large speakers in

cabinets because the cabinet may divert the high frequency

signals to a small speaker (a tweeter) because the large

main speaker is poor at reproducing them.

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+

-

3.8 ON/OFF SWITCH

Switch is used to isolate both live and neutral connectors.

Fig 3.9 switch symbol

There are three important features to consider when

selecting a switch

Contacts: e.g. single pole, double pole

Rating: maximum voltage and current

Method of operation: toggle, slide, key.

1. Switch contacts: several terms are used to describe switch

contacts. The simplest on/ off switch has one set of contacts

(single pole) and one switching position which conduct

(single throw). The switch mechanism has two positions.

Open (off) and closed (on), but it is called single throw

because only one position conducts.

2. Switch contact rating: switch contacts are rated with a

maximum voltage and current, and there may be different

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ratings for AC and Dc. The AC values are higher because

the current falls to zero, many times each seconds an arc

is less likely to form across the switch contact. For low

voltage electronics projects the voltage ratings will not

matter, but you may need to check the current rating.

3. Method of operation: toggle, sliver, key.

CHAPTER FOUR

4.0 PRINCIPLE OF OPERATION

The detector circuit presented here needs no additional

power supply. It employs an electrolytic capacitor to

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store adequate charge to feed power to the alarm circuit,

which sound an alarm for reasonable duration of time

when it detect mains failure

During the presence of mains power supply, the

rectifier Diodes ( IN4007) are used to convert alternating

circuit ( Ac) to direct current (DC) by stepping the voltage

down to a required level. Resistor (R1 and R2) to reduce the

flow of electric current in the circuit. Capacitor (c3) filter and

removes the fluctuation or pulsation called ripples present in

the output voltage supplied by the rectifier, this operation is

performed or carried out by a large value electrolytic

capacitor ( 100μf 25v) connected across the Dc supply to act

as a reservoir, supplying current to the output when the

varying Dc voltage from the rectifier is falling. A zener diode

is used to limit the filtered voltage to 15-volt level and to

maintain a fixed voltage. They are designed to breakdown in

a reliable and non-destructive way.

The mains presence in a phase is indicated by a Red

LED. This emits light when an electric current passes through

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it. Resistor (R5) is connecting in series with LED to limit the

flow of current flowing to the LED. Diode (D6) and resistor

(R7) connect in series with the base of transistor PNP (T1) to

reduce and forward biase the electric current flowing to the

transistor. Capacitor (C2) serve as filter and store electric

charge.

The low level Dc is used for charging capacitor (C3) and

reverse biasing switching transistor (T1). This, transistor (T1)

remains cut-off as long as the mains supply in present. As

soon as the mains supply fails, the charge stored in the

capacitor acts as a power supply source to transistor (T1).

Since, in the absence of phase supply source, the base of

transistor is pulled low via resistor (R8), then it conducts and

sound the buzzer (alarm) to give a warning of the phase

power failure.

With the value of capacitor (C3), a good quality buzzer

sound for about a minute. By increasing or decreasing the

value of capacitor (C3) this time can be altered.

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At a high DC voltage level, transistor T1 (BC558) may pass

some collector –to – emitter leakage current, causing a

continuous murmuring sound from the buzzer. In the case,

(T1) can be replace with some low-gain transistor.

CHAPTER FIVE

5.0 CONCLUSION

This project has made us to understand not only the function

of some of the electronic components, but also to provide a

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detector that would sound alarm in event of phase supply

failure in transformer.

During circuit construction, we took time in fixing the

components, this is because any mistake would lead to the

damage of the components and also increase the cost of the

circuit construction .

It would be nice for the up coming electrical electronic

engineering student to start participating seriously in

practical. We plead to the department of electrical

electronics engineering to also establish a compulsory

seminal or laboratory for all power engineering students so

that they would understand most Electrical and Electronics

components before they commence their project.

5.1 RECOMMENDATION

A project like this is effectively a complement of class room

work. The sole aims of students final year project is to

ascertain how well the students have understood and are

able to apply appropriately all the theories, principles, laws,

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components identification and function which is acquired in

the process of knowledge economy.

Therefore, at the end of this project the students should

be able to identify some components on the circuit board,

read circuit diagram, prepare layout diagram and be able to

fix the components on the Vero-board in accordance with the

layout diagram. The student will also be expected to know

how to carryout soldering work and trouble shouting on an

electronic device.

The project has not been easy considering all that are

committed to realizing it. It is an inevitable challenge yet

remains puzzles to most students carrying out such project,

Knowing what it entails. Therefore, it is up to students to

start on time to prepare for it, in order to run away from any

hitch that may hinder the process of the project

construction. Students are advised to attend classes, read

their books adequately, make research and ask question to

clarify doubt. All these are strategies prepare one for such

project design and construction. This project phase fault

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detector in power transformer is interesting and educating

one and it has taken us into advancement in Electrical and

Electronics regulation.

Nigeria as a third world country needs technological

advancement in different sectors of her economy especially

in this age of digitalization and computerization. Phase fault

detector in power transformer should be introduce into

power system in Nigeria. We also recommend that the

management should aid by providing some of the scarce and

expensive components to the students at subscribed rate.

We strongly recommend the use of this detector for power

transformer because we have been opportune to praticalize

and appreciate the theories.

REFERENCE

J.B Gupta power system 10Th Edition 2007-2008 Reprint, Part

iii page 66-105.

Short circuit calculation by Mercedes www.goggle.com/short

circuit-calculation-methods.

Prof. J. Rohan Lucas “Power system Analysis”

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www.elect.mrt.ac.ik/EE423%fault analysis note.pdf.

Ashfaq husseins “ electrical power system” 4th Edition

Massimo mitolo PHD “short circuit calculation methods”

http//ecmweb.Com/mag/electric-short-circuit-

calculation-methods.

B.L. Theraja and A.K. Theraja (2002) Electrical technology:

New Delhi S. chad and company Ltd.

http//www.electronicsforyou.com

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