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Abstract
The project is designed to provide uninterrupted AC mains supply i.e., 230 volt to a single phase load. This is achieved by automatic changeover of the load from the missing phase to the next available phase in a 3 phase system. It is often noticed that power interruption in distribution system is about 70% for single phase faults while other two phases are in normal condition. Thus, in any commercial or domestic power supply system where 3 phase is available, it is advisable to have an automatic phase sequence selector system for uninterrupted power to critical loads in the event of missing phase. In this system auto selection is achieved by using a set of relays interconnected in such a way that if one of the relay feeding to the contactor load remains energized always. Under the phase failure condition the corresponding step down transformer secondary delivers zero voltage to that relay and the relay will switch to it NC position allowing it actuate the other contactor sequentially for power to continually supplied to a single phase output.
TABLE OF CONTENT
DEDICATION ii
DECLARATION iii
STATEMENT 1 iv
STATEMENT 2 v
Acknowledgement vi
Abstract vii
TABLE OF CONTENT viii
CHAPTER ONE 1
1.0 INTRODUCTION 1
1.1 BACKGROUND OF STUDY 1
1.2 OBJECTIVES OF STUDY 2
1.3 SIGNIFICANCE OF STUDY 3
1.4 SCOPE OF THE STUDY 3
1.5 LIMITATION OF STUDY 3
CHAPTER TWO 4
2.0 LITERATURE REVIEW 4
2.1 REVIEW OF PAST WORKS 4
2.2 PARTS AND COMPONENT REVIEW 5
CHAPTER THREE 15
3.0 METHODOLOGY 15
3.1 SYSTEM DESIGN AND IMPLEMENTATION 15
3.1.1 THEORY ANALYSIS 15
3.1.2 SYSTEM DESIGN ANALYSIS 23
CHAPTER FOUR 29
4.0 CIRCUIT OPERATION 29
4.1 HOW IT WORKS 29
4.2 RESULTS AND DISCUSSIONS 29
4.3 TESTING PROCEDURES 30
4.4 RESULT ANALYSIS 30
4.5 RESULT TABLES 30
CHAPTER FIVE 34
5.0 CONCLUSION 34
5.1 RECOMMENDATIONS 34
REFERENCES 36
CHAPTER ONE
1.0 INTRODUCTION
Power instability and phase failure has posed serious threat to the economy of the nation. In most developing countries, the power sector has been trouble by high technical lack of losses a lack of cost recovery pricing, poor maintenance, low equipment reliability, high staff levels, productivity, Corruption, a crippling non payments problem and mounting debt. These factors have resulted in the commercial unsustainability of many developing countries power sectors, which unable to attract the needed private investment (Kuale and Tsado, 2006). The lack of reliable power and other infrastructure has had a notably adverse impact on the industrial growth and individual development and these has contributed to perpetuating poverty (Bacon,1995). That is to say, where there is an erratic power supply there is less development; one of the factor that boost the economy is the availability of steady and stable power supply.
However, most companies, industrial, commercial and even domestic are dependent on public power supply which have erratic supply such as Phase failure, Phase Imbalances or Total Power Failure due to technical reason which can be that, power lines are over loaded resulting to a trip of power by the switch gear, fuses in the feeders are broken, or load shading process undertaken by the distribution company.
In a case where a single phase public utility prepaid meter is operated with a single phase power supply unit and there is phase failure from the public, utility power supply, the prepaid meter will stop reading. At this point if the phase is not manually changed, power will be out for the user, that is to say someone needs to be present always to make the changes at any point in time. But to overcome these protocols, automatic phase sequence selector system need to be used.
1.1 BACKGROUND OF STUDY
The need to meet the power requirements of the people lead to the construction of automatic phase sequence selector system. Although the government has made efforts to stabilize power generation in the country. In 1998 when the national council on privatization ( NCP) empowered a 23 member Electrical sector Reform Implementation Committee (ERIC) to develop guidelines to promote the policy goals of the total liberalization, competition and private sector lead growth of electricity sector, this is to ensure that Nigeria has electrical power Industry (EPL) that can meet the needs of its citizens in the 21st century (Asubiojo 2007). Irrespective of these effort, the power is still suffering from instability. Power generated and distributed has its own challenges which could be fault on the line, short circuit, phase failure etc, denying the people asses to the available power. This has led to the need for automatic phase sequence selector system.
The automatic phase sequence selector is a system that can select the next available phase when there is a phase failure. It is also design in such that it select the phase with a normally voltage. For a preferred phase a manual selection is on the system.
The system consists of three main parts namely:
The Transformer
Voltage Regulator and
The Electrical Switching Device (Relay)
Some other important components are Capacitor, Indicator Lamp, Circuit breakers and Circuit board. The indicator lamp displays the available line with voltage, the 4 pole circuit breaker is used to connect the 3 phase supply to the system, and the Transformers step down the voltage (230v / 12v), then rectified the voltage and pass it through the regulator in order to drive the relays. The relay switch is used to actuate the contactor. The contactors are used in order to carry the load.
1.2 OBJECTIVES OF STUDY
The main aim of the project is to present an automatic phase switching for 220V alternating current. Other aim includes:
- To develop a simple low cost device aimed at easing the prevalent burden faced by delicate offices, parastatals and institutions who need very low but constant power supply.
- In a situation where there is power on the distribution line and a phase trip off due to over loading or other reason. The automatic phase sequences selector therefore erases a setback that may occur as a result of power outage.
iii. To stimulate the interest of upcoming students to take up research not only in their field of study “Electrical / Electronic Engineering “ but also to extend their arms to other discipline, thus enhancing the versatility of Electrical / Electronic Engineering.
iv To create awareness that will stimulate the interest of fellow students who intend to take up research topic on automatic switch of any type.
1.3 SIGNIFICANCE OF STUDY
The significance of the project work cannot be overemphasized, because the hazard associated with electricity is very high. Thus the study signifies that:
- The risk involved in the manual control or switching has been totally eliminated by the automatic control.
- The application of the project work would reduce manual labour and cost of maintenance of manual switching devices.
- The project work has a protective device that will automatically switch off the system and protect the load during a fault situation.
- Accident can occur as a result of manual control can be eliminated.
- The application of the project work will definitely remove stress and down-time industries were constant single phase is required.
1.4 SCOPE OF THE STUDY
The scope of the project covers the applications, which is either domestic or industrial purpose, its features and advantages; also the component used for the constructions. It also covers the importance or the need for the project work.
1.5 LIMITATION OF STUDY
Without reliable and comprehensive data, this project was faced with lack of proper information need for analysis and comparison. Again due to the problem of mobility and finance; this project suffered a setback in acquiring the equipment and facility need; it was also an uphill task to get all the necessary component need for the circuit construction.
Complete Material Cost #3,000
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