Design And Construction Of A Single Phase Automatic Changeover Switch With Generator Trip-Off

The Changeover Switch is a device used to switch off a power supply and subsequently switch on another power supply.

An Automatic Changeover Switch switches off the generator and automatically changes over to NEPA. This Automatic Changeover Switch will automatically switch off your generator and change over to MAIN (Public power supply/NEPA) on resumption. You will save fuel and no risk of electrocution. It also serves as power surge protector for appliances.

The main aim of any electric power supply in the world is to provide uninterrupted power supply at all times to all its consumers. Although, in developing countries, the electric power generated to meet the demands of the growing consumers of electricity is insufficient, hence power instability and outage. 

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRCT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• STATEMENT OF PPROBLEM
• AIM/OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• PURPOSE OF THE PROJECT
• LIMITATION OF THE PROJECT
• APPLICATION OF THE PROJECT
• DEFINITION OF TERMS
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

2.0      LITERATURE REVIEW

2.1      REVIEW OF ELECTRICAL PHASES

2.2      REVIEW OF THREE-PHASE ELECTRIC POWER

2.3     REVIEW OF CAUSES OF POWER FAILURES

2.4       POWER SUPPLY RELIABILITY

CHAPTER THREE

3.0      CONSTRUCTION METHODOLOGY

3.1      BLOCK DIAGRAM OF THE SYSTEM

3.2      CIRCUIT DIAGRAM

3.3      CIRCUIT DESCRIPTION

3.4      SYSTEM OPERATION

3.5     COMPONENTS LIST

3.6     DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

4.0       RESULT ANALYSIS

4.1      CONSTRUCTION PROCEDURE AND TESTING

4.2      ASSEMBLING OF SECTIONS

4.3      CONSRUCTION OF THE CASING

4.4      ECONOMIC OF THE PROJECT

4.5     PROJECT VIABILITY

4.6      PROJECT RELIABILITY

4.7      PROJECT MAINTAINABILITY

4.8     PROJECT EVALUATION

4.9     TESTING, TROUBLESHOOTING AND REMEDY

CHAPTER FIVE

• CONCLUSIONS
• RECOMMENDATION

5.3     REFERENCES

CHAPTER ONE

• INTRODUCTION

A power changeover circuit for selectively connecting an electrical load to one of two available power sources, preferably alternating current sources, wherein one of the sources constitutes an engine driven generator requiring a predetermined time to reach specified output characteristics after energization. Relay operated changeover switch means selectively connects the load to either of the electrical power sources, and second switch means in series with the changeover switch located between the changeover switch and the engine driven power source delays connected of the generator source with the load after disconnection of the load from the other source until the generator output reaches specified characteristics [2]. Further, the circuit provides for the disconnection of the load from the generator upon deenergization of the generator, and prior to the changeover switch connecting the load to the other supply source in order to prevent arcing. Relays, resistors and time delay switch devices are utilized in the circuit to provide the desired operation [3].

1.1                                         BACKGROUNDOF THE PROJECT

Due to inconsistent supply of power, there is a growing need for an alternative source of power supply. This has lead to heavy capital investment in a bid to suppress power failure and ensure regular power supply for the industry, hospitals, schools and homes. The problem of power failure can be checkmated with the use of stand-by generating set [4].

An Engineering Author, “Terrell Croft” said in his book titled “Upgraded Signal Source with Improved Performance and Reliability” that the cost and depredation associated with breakdown vary from one application to the other, and in some cases, the user has little choice but to ensure that a stand-by unit is available to take over on event of failure of primary system [5].

If some of these big firm do not make provisions for stand-by power source, frustration could set in which may lead to the closure of business and thus throwing workers into unemployment. Also in the case of hospital, undergoing a surgical operation and power supply suddenly go off, the patient might loose his or her life due to the power outage [4].

Furthermore, if the president of the country is making nationwide broadcast and all of a sudden power went off in the transmitting station, it would be viewed as an attempt to sabotage the government ruling and some people must pay for it [1][2].

In his book, Terrell Croft also said that the depredation caused by such reduce efficiency of the organization and leads to a great deal of frustration.

Sequel to the rate at which more sophisticated electrical/electronics gadgets are being procured and installed in our homes, hospitals and business premises, there is a justifiable need for a faster and more reliable change over system in an event of power outage.

The Changeover system switches off a power supply and subsequently switch on another power supply. Basically it is aimed at switching on a more convenient power supply to the load.

Since it switches on power to the load, precautions has to be taken while choosing the type of Change Over Switch, while selecting the appropriate size, the control of arcing has to be put into consideration [3].

A good switch should be the one whose contact is made in such a way as to limit the arc formation by having no contact-bounce and by having contacts made of good conductive, corrosion resistance and wear resistance materials.

A good change over switch must have adequate insulation and must be so constructed and located as not to constitute a potential hazard [5].

A good change over switch should also have tight contact points so as to limit or eliminate the possibility of partial contact at the contact point. The partial contact leads to overheating of the components and may lead to fire outbreak in the entire room [5].

1.2                                                  PROBLEM STATEMENT

Power failure or outage in a country, state or city is highly detrimental to development in public and private industries. The insecurity associated with constant or frequent power failure or outage brings about limitation to power consistent investments, thus hampering the development of industries and multinational ventures. Processes like carrying out surgical operations in hospitals, laboratories which require constant power supply for research, money transactions between banks and more require constant use of uninterrupted power. In other to solve this problem, an automatic changeover switch was invented. This research covers the design and construction of a single phase automatic power changeover. It has the capacity to automatically switch power from  national grid to generator and vice versa, once there is power failure in any of the two power supplies and at the same time has the capacity of shutting down a generator set once the mains grid is been restored.

1.3                                                 AIMS AND OBJECTIVES

The main aim of any electric power supply in the world is to provide uninterrupted power supply at all times to all its consumers, a device which switches on the head from power Holding Company (PHC) to a generator when power fails and from generator to PHC when power comes back, using relay as the switching device.

1.4                                         SIGNIFICANCE OF THE PROJECT

The automatic change over switch, the switch aimed at achieving the following automatic actions [2][3][4];

• To change power over to generator
• To change back to PHC
• To change the generator.

The automatic change over unit can be operated in single or three phase system. The automatic change over switch has the following advantages;

• It minimizes damages to lives/equipment since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error.
• It reduces its change over timing to the minimum due to its fast response to power outage.
• It maintains high quality of service through its fast and prompt response.
• Moreover, the size and captivity of the unit will depend upon the load for which it will be used. The unit is also portable, easy, convenient and safe to install.
• Genset is put off automatically when main power resumes.
• Minimized physical activity is to start the generator.
• It can operate in low voltage.
• Fuel is saved due to auto stop facility.

1.5                                         PROBLEMS OF THE PROJECT

In every home, office or industries, automatic power changeover plays a vital role, that is, It provides a means of switching from utility AC mains to generator in the case of power failure; This project has been improved on the existing types of electromechanical device that has being in use over the years.

In the course of designing this project, different kinds of problem was notice such as [4][6]:

1. Difficulty in troubleshooting with circuit without the circuit diagram
2. Difficulty in connecting the output without short-circuiting, until a multiplexing circuit was gotten.

• Difficult in wiring because of the strong wiring the project required.

1.6                              SCOPE AND LIMITATION OF THE STUDY

This work covers only a one phase automatic changeover which can only be used for providing a means of switching from one phase of AC mains to another in the case of failure in public utility. It is limited to

1. Phase – one phase
2. Capacity – single Phase

• Input Volt – 220v

1.7                                      APPLICATIONS OF THE PROJECT

1. This circuit can be used as a home lighting system with few modifications.
2. It can be used to drive other DC loads like a DC motor of any electronic appliance or other toy applications [4].

1.8                                             DEFINITION OF TERMS

CHANGEOVER: Generally, a changeover switch is a system which could be operated manually or automatically , that changes one source of power supply to another source in case of power failure from either of the two sources.

RELAY: relay is one of the major components used in this work which is an electrical device, typically incorporating an electromagnet, which is activated by a current or signal in one circuit to open or close another circuit.

POWER FLUCTUATIONS: is a periodic dip or spikes in the electrical current of any given circuit.

POWER FAILURE: is a short- or long-term loss of the electric power to an area.       

1.9                                         METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit was carried out.

• Finally, the whole device was cased and final test was carried out.

1.10                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this works is on the introduction to changeover switch. In this chapter, the background, significance, objective limitation and problem of changeover switch were discussed.

Chapter two is on literature review of changeover switch. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.