ABSTRACT
Reliable electricity supply is essential for development. As a result, demand for
electricity has continued to increase globally, occasioned by the fact that
electricity is highly portable and can be transformed from one form to another to
meet needs. In Nigeria and most developing countries, electricity supply from the
public utility is not only insufficient but highly erratic. The effect of this is adverse
on critical and sensitive infrastructure that depend on uninterrupted power
supply. Hence, many domestic, industrial and commercial consumers are
compelled to acquire one form of alternative source of power supply or another.
With this however, when different power schemes are interconnected, there
arises the challenge of switching between the power sources not only smoothly,
but in a manner that optimizes their use. Solving these challenges forms the focus
of this work. This design monitors three independent power sources: Utility Grid
of Power Holding Company of Nigeria (PHCN), solar and generator and engages
them following preset conditions in a microcontroller. A software program in
assembly language drives the microcontroller. Preference is given to the PHCN
line, but in the event of failure or abnormal conditions in the PHCN line, the
system will effect a changeover automatically to the solar source through
contactors, provided the output of the solar source is acceptable, else the system
will initiate the starting of the generator and transfer of load to same. This system
finds application wherever there is unreliable power supply and interconnected
power schemes.
TABLE OF CONTENTS
TITLE PAGE i
APPROVAL PAGE ii
CERTIFICATION iii
DECLARATION iv
DEDICATION v
ACKNOWLEDGEMENT vi
ABSTRACT vii
TABLE OF CONTENT viii
CHAPTER ONE INTRODUCTION 1
1.0 Project background 1
1.1 Statement of problem 2
1.2 Project objectives 2
1.3 Significance of project 3
CHAPTER TWO LITERATURE REVIEW 4
2.0 Electricity in Nigeria 4
2.0.1 Nigeria’s Electricity Sector in Retrospect 5
2.0.2 Nigeria’s Power Sector Reform 6
2.0.3 Electricity Power Sector after Privatisation 8
2.0.4 Electricity Production and Consumption in Nigeria 11
2.1 Electricity from Solar 13
2.1.0 Components of a PV system 14
2.1.1 Design Considerations 20
2.1.2 Energy from the PV module 21
2.2 Use of Generators 22
2.3 Transfer Switches 23
ix
2.3.0 Types of Transfer Switches 24
2.3.1 Applications of Closed Transition Transfer Switch (CTTS) 25
2.4 Uninterruptible Power Supplies (UPS) 26
2.5 Microcontroller and Embedded systems 26
2.5.0 The 89C52 Microcontroller 27
2.6 Comparator 38
2.6.0 Comparator parameters 39
2.6.1 Comparator applications 43
2.7 Relay 45
2.8 Contactor 46
2.8.0 Contactor Operation 48
2.9 Step down transformer 49
CHAPTER THREE METHODOLOGY 51
3.0 Introduction 51
3.1 Design Stages: Circuit Simulation 55
3.2 Voltage Monitoring 57
3.2.0 Step down transformer 57
3.2.1 Rectifying circuit 58
3.2.2 Filtering and smoothing circuit 60
3.2.3 Voltage detection circuit 62
3.3 Realizing the Software 64
3.4 Switching circuit 66
CHAPTER FOUR SYSTEM DESIGN AND IMPLEMENTATION 68
4.0 Selection Of Components 68
4.1 Contactor Design 68
4.2 Voltage Monitoring Circuit Design 69
CHAPTER ONE
INTRODUCTION
1.0 Project Background
Electricity is of enormous importance to the society today. It is indispensable to
social and economic development. Modern industrial systems depend on regular
supply of electricity. Quality of life and standard of living today depend much on
electricity. People need energy in one form or the other (heat, light, sound etc)
and electricity is most convenient in that it can be converted with ease from one
form to another.
However, in many developing nations steady availability of electricity is yet to be
realized. In Nigeria, for instance, the supply of electricity from the public utility
(PHCN) is unreliable, marked by incessant outages, and therefore inadequate for
any meaningful advancement in industrial, commercial and domestic activities.
Generators are commonly used in Nigeria but the cost of running diesel or other
fuel for running generators all the time is not feasible for both home and business
concerns. Renewable sources like solar are also used but so far there is yet room
for improvement before solar power can be utilized without some form of
backup. Thus, multi-tier power supply, a system of more than one power source,
has gradually become the norm in our society.
This project “Monitoring and Control of 3-tier Power Supply” provides a way of
monitoring and switching between three different power sources in order to
optimize their use.
2
1.1 Statement of Problem
The demand for energy especially electrical energy is on the increase globally and
power utilities strive to match supply with demand. A lot of large-scale industrial
critical loads suffer from voltage interruptions and sags which can cause a
significant financial loss [1]. In Nigeria the actual generating capacity falls short of
the installed capacity and the country’s peak demand due to problems in the
power systems network [2]. The country requires over 6000 MW of electricity to
meet present demand. Current output is around 3000MW, much of which is not
put to use due to poor power transmission and distribution infrastructure [3]. The
effect is that supply from the national grid has been very low and unsteady over
the years with the result that people have resorted to integrating multiple power
sources as a remedial measure.
The problem is the need to monitor these power sources and switch between
them in a manner that ensures safety of personnel and equipment. There is also a
need to optimize their use by setting the preferred power source as default
through some device.
1.2 Project Objectives
The objectives of this project include:
1. To monitor and control a three tier power supply system.
2. To automate the power changeover process to ensure a smooth transfer of
load for the purpose of safety and convenience.
3. To implement a system of power change over with minimal time wastage.
4. To optimize power use in a system of 3 power sources by setting the most
economical power source as default in the system.
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