Design And Construction Of An Automatic Three Phase Power Changeover With Surge Protector

ABSTRACT

This project work is on the design and construction of automatic power changeover for 3-phase power supply. It provides a means of switching from one phase of AC mains to another in the case of failure in the existing phase or under-voltage, and also automatic power changeover from public utility supply to generator and vice versa was aimed at providing a useful system for use in our homes or offices. The system was achieved with a 66A 3-Ф contactor, 100mA transformers and relays. The system turns on a generator when the public utility (PHCN) is off by cranking the starter and a provision was made to stop cranking when the generator is fully started. This project has been improved on the existing types of electromechanical device that has being in use over the years.

Hence this has been achieved by the use of operational amplifier, timing circuit and high current relay switches and it is powered by 12V dc power supply.
The aim of this work is to overcome power fluctuation/phase, 0r interruption by changing to the next most healthy available phase to feed the equipment without any notice of power outage comparactor, multiplexing, relay and surge protecting circuit.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• AIM/OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• STATEMENT OF PROBLEMS
• LIMITATION OF THE PROJECT
• PURPOSE OF THE PROJECT
• APPLICATION OF THE PROJECT
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

2.0     LITERATURE REVIEW
2.1     REVIEW OF ELECTRICAL PHASES
2.2     REVIEW OF THREE-PHASE ELECTRIC POWER
2.3     REVIEW OF THREE PHASE GENERATION AND DISTRIBUTION
2.4   REVIEW OF THREE-PHASE LOADS

2.5     OVERVIEW OF RELEVANT TECHNOLOGY

2.6     REVIEW OF RELATED WORKS EXISTING SYSTEM

2.7     SUMMARY OF REVIEWED WORKS

CHAPTER THREE

3.0      METHODOLOGY

3.1     BLOCK DIAGRAM OF THE SYSTEM

3.2     DESCRIPTION OF SOLAR INVERTER UNITS

3.3     SYSTEM CIRCUIT DIAGRAM

3.4     CIRCUIT OPERATION

3.5     THREE PHASE INPUT TO SINGLE PHASE OUTPUT

3.6     DESCRIPTION OF COMPONENTS USED

CHAPTER FOUR

RESULT ANALYSIS

4.0     CONSTRUCTION PROCEDURE AND TESTING

4.1     CASING AND PACKAGING

4.2     ASSEMBLING OF SECTIONS

4.3     TESTING OF SYSTEM OPERATION

4.4     COST ANALYSIS

CHAPTER FIVE

5.0     CONCLUSION

5.1     RECOMMENDATION

5.2     REFERENCES

CHAPTER ONE

• INTRODUCTION

In Nigeria today the problems of power outage across phases is so rampant thus leading to some sensitive equipment and appliances being redundant, this could sometimes be the cause of one phase going out with respect to the other.

It may surprise one to note that in an attempt to solve this problems, so many unskilled electricity consumers has in recent past resorted to some crude means of swapping between phases to obtain power. So many souls have been lost in this act. This is an undesirable condition to consumers and the need now arises to design a device that can automatically select among the phases and make power supply available at the consumers terminal.

However, this can only be possible if one have a three phase met or and there is supply from any of the service line or the entire line, this project known as a three phase automatic changeover which has been constructed with a view of solving the problems stated above. The design and construction was based on the principle of Electro magneto-Dynamism and alignment as demonstrated in the contactor arrangement.

Among other components are the timers miniature-circuit breakers the contactors and indicator bulbs, the ease with which the device is operated is well elaborated to ensure simplicity effort were made to present a stop by step operation of the project. As much as there is no project without limitation and applications, we have as well dedicated a section of this paper to look into it.

In order to ease the effort of technicians in restoring the devices should there be any malfunction associated.

Faults and how they are cleared is presented, however, there are no user serviceable parts in the device therefore all maintenance should be referred to a qualified electrical personnel.

For the load protection, a surge protector is used. This device is used to prevents the peak AC voltage from going above a certain threshold such as plus-or-minus 200 volts.

A surge protector limits the voltage supplied to an electric device by either blocking or shorting current to reduce the voltage below a safe threshold. Blocking is done by using inductors which inhibit a sudden change in current. Shorting is done by spark gaps, discharge tubes, zener-type semiconductors, and MOVs (Metal Oxide Varistors), all of which begin to conduct current once a certain voltage threshold is reached, or by capacitors which inhibit a sudden change in voltage. Some surge protectors use multiple elements.

The most common and effective way is the shorting method in which the electrical lines are temporarily shorted together until the voltage is reduced by the resistance in the power lines. The spike’s energy is dissipated in the power lines (and/or the ground), converted to heat. Since a spike lasts only 10s of microseconds, the temperature rise is minimal. However, if the spike is large enough, like a nearby hit by lightning, there might not be enough power line or ground resistance and the MOV (or other protection element) can be destroyed and power lines melted.

Surge protectors for homes can be in power strips used inside, or a device outside at the power panel. A modern house has three wires, Line, Neutral, and Ground (L,N, and G). Many protectors will connect to all three, in pairs, L-N,L-G,and N-G, since there are conditions, like lightning, where both L and N have high voltage spikes that need to be shorted to ground.

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.

1.4                               PURPOSE OF THE PROJECT

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

• OBJECTIVE OF THE PROJECT

The objective of this work is to design a device that will overcome power fluctuation in the phase or interruption by selecting next most healthy available phase to feed the Equipment, to change power over to generator, to change back to PHC to change the generator, and to protect loads from damages due to peak AC voltage or surge using surge protector switch.

1.3                                      SIGNIFICANCE OF THE PROJECT

Industries require three phases power to run their machinery. Some of them require continuous \ uninterrupted power to maintain their data. Auto changeover unit for those equipments whose supply is single phase. The single phase supply is selected automatically from three phases supply.

Auto three phase power changeover introduces an automatic solution to overcome power fluctuation \ phase interruption by selecting next most healthy available phase to feed the equipment.

This automatic change over unit operates in 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.

1.4                         LIMITATION OF THE PROJECT

In every home, office or industries, automatic changer plays a vital role, that is, It provides a means of switching from one phase of AC mains to another in the case of failure in the existing phase; 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:

• Difficulty in troubleshooting with circuit without the circuit diagram
• Difficulty in connecting the output without the three phases short-circuiting, until a multiplexing circuit was gotten.
• Difficult in wiring because of the strong wiring the project required.

1.5                                 SCOPE OF THE STUDY

This work covers only a three phase automatic changeover which can only be used for providing a means of switching from one phase of AC mains to another or from generator to utility supply in the case of failure in the existing phase. The surge protector prevents the peak AC voltage from going above a certain threshold such as plus-or-minus 200 volts. Semiconductor devices are used for this purpose.

1.6                           APPLICATION OF THE PROJECT

This device is used in the following places:

1. home,
2. office,
3. worship places
4. workshops or industries

1.7                                         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 digital changeover circuit.

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

1.8                                             DEFINITION OF TERMS

POWER OUTAGE / POWER FAILURE: A power outage is the loss of the electrical power network supply to an end user.

AUTOMATIC CHANGEOVER is device that automatically transfers power from generator supply to PHCN supply when available and stops the generator without without human intervention

1.8                                             PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.