Design And Construction Of Automatic Changeover Switch With Indicator

ABSTRACT

This project work deals on the design and construction of an automatic power changeover that will change/transfer control from MAINS to Gen set and can switch ON/OFF the Gen automatically. The system integrates phase selector in MAINS and changeover to Gen. It is designed in several blocks all combined to from one functional unit. A +5v regulated DC power supply unit forms the first block whose output is fed to priority encoder and decoder block. The output of the BCD – Decimal decoder is used to select the phase in priority through a transistor driver stage and electromagnetic relay that activates contactors. The least prioritized phase is the Gen set which contains a circuitry that automatically starts and stops the Gen set. The system is realized with TTL chips market. LEDs and AC panel lamps are used to indicate the status of the system while a manual switch is used to demonstrate the mode of operation of the system.

 TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PROBLEM STATEMENT
• 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

2.5      OVERVIEW OF CONTRACTOR

 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

1.0                                          INTRODUCTION

Industrial automation and control has contributed immensely to the high rate of the world’s technological growth. Power control and automation is a part of this field which is applied in virtually anywhere electrical power is used, generated or transmitted. Manual power change-over switches have been in existence and in different forms and shapes. 1959, the advent of microelectronics has paved way to modify the manually operated change-over switches. This project deals with the design and construction of automatic change-over switch with indicator. It eliminates the time and energy spent in operating the manual change – over and starting of Gen. Set. It is fully automated. It can be used in residential houses, offices and most importantly, in factories that required constant power supply. It has so many advantages over the existing ones/types.

This project work is embarked upon to eliminate nearly every shortcomings associated with the manually operated type to ensuring that it is fully automated.

The fourth is the driver stage which comprises of NPN transistor that energizes the electromagnetic relay which switches the phase in priority. The Gen set switching section is achieved using the least prioritized phase. This section switches ON the Gen set when all the NEPA phases are low, OFF or faulty. Once the Gen set phase is selected, a switching transistor fires an SCR which conducts large battering current to the ignition coil of the Gen set. Panel indicators are used to show the status of the system.

• BACKGROUND OF THE STUDY

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.

An Engineering Author, “Tony Rudkin” 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.

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.

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.

In his book, Tony Rudkin 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.

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.

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 over heating of the components and may lead to fire outbreak in the entire room.

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 digital 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                                 OBJECTIVES OF THE PROJECT

The major objectives of this project is to design and construct an automatic change-over switch with Gen set switching facility capable of transferring control from MAINS to Gen set.

It is also aimed at equipping the graduating student with Hands – on experiences which is invaluable in their professional practice. It is aimed at grounding the graduate of EEE in electronic system designs involving power control and automation using random/Hard wired logic. Another objective of this project is to acquaint the graduating students on the ethics of Engineering, technical and scientific writing which is a nucleus of engineering professional practice.

1.4                                 SIGNIFICANCE OF THE PROJECT

This project work signifies a lot in Electrical power control and automation. It means a lot in EEE. This project is a design that has to be developed and funded for commercial purposes regarding its usefulness. This project eliminates the stress, time delay and other drawbacks in manually operated types. The project can be modified to display the phase in use at a particular time using a single seven segment Display and its appropriate circuitry.

1.4.                                SCOPE OF THE STUDY

This project work focuses on the design and construction of automatic change-over switch with Gen set switching facility. It covers the following; Encoders and Decoders, Relays/Contactors, 3 – phase regulated DC power supply unit, passive and active components, Generator switching mechanism.

1.5                                              PURPOSE OF THE PROJECT

The main purpose of this work is to provide a means of having uninterruptible power supply in our home, office, workshops or industries.

1.6                                         SIGNIFICANCE OF THE PROJECT

The automatic change over switch, the switch aimed at achieving the following automatic actions;

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

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 changeover 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.

1.7                                            BENEFIT 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 electromagnetically device that has being in use over the years.

1.7                                        LIMITATION OF THE PROJECT

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 generator set in the case of failure in public utility.

1.8                                     APPLICATIONS OF THE PROJECT

This device provides constant power supply in our:

• Homes
• Workshops
• Worship centre (such as churches or mosque)
• Offices
• And any other places that electrical energy is been used

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 changeover was carried out.
2. Studying of various component used in circuit.
3. Construct a changeover circuit.

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

1.10                                          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.       

Blackouts: a term used to describe a mains power supply failure, also referred to as an Outage.

Circuit-Breaker: a device inhibiting high surge currents over a set stated figure. Under such conditions the breaker will operate and the circuit is isolated.

Generator: a device that converts Kinetic energy generated from combustion into electrical energy to provide an ac or dc power source to a load.

1.11                                      PROJECT WORK ORGANIZATION

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 work is on the introduction to this study. In this chapter, the background, significance, scope, objective, the need (benefit), limitation and problem, advantages of this work was discussed.

Chapter two is on literature review of the study. 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.