Design And Construction Of A Phase Failure Detector For Three Phase Power Supply

ABSTRACT

Electrical power system engineering comprises power generation, transmission, distribution, and the utilization of electricity. Modern trends in the development of electric power systems explore means of improving efficiency in these stages mentioned. On the demand side, the protection of consumer equipment and appliances from damage and total destruction due to phase failures is an issue of paramount importance mainly in parts of the world with unsteady supply of electricity. In this work we took a detailed look into what a phase failure is and the possible causes. Then we finally explain the details of a method we have developed that detects cases of phase failure and takes the appropriate measure that will save the consumer loads from damages.

TABLE OF CONTENTS

TITLE PAGE

CERTIFICATION

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENTS

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• SCOPE OF THE PROJECT
• APPLICATION OF THE PROJECT
• LIMITATION OF THE PROJECT

CHAPTER TWO

• REVIEW OF RELATED LITERATURES
• REVIEW OF ELECTRICAL PHASES
• REVIEW OF THREE-PHASE ELECTRIC POWER
• REVIEW OF THREE-PHASE LOADS
• CONSEQUENCES OF A POWER FAILURE
• TYPES OF POWER FAILURE
• PROTECTING THE POWER SYSTEM FROM FAILURE
• RESTORING POWER AFTER A WIDE-AREA OUTAGE
• POWER FAILURE INEVITABILITY AND ELECTRIC SUSTAINABILITY
• MITIGATION OF POWER OUTAGE FREQUENCY

CHAPTER THREE

• DESIGN METHODOLOGY
• SYSTEM CIRCUIT DIAGRAM
• SYSTEM MODE OF OPERATION
• MAJOR COMONENTS DIAGRAM
• OPERATION PRINCIPLE OF A CONTACTOR

CHAPTER FOUR

• INSTALLATION OF THE COMPLETED DESIGN
• CONSTRUCTION PROCEDURE AND TESTING
• CASING AND PACKAGING
• ASSEMBLING SECTION
• TESTING OF SYSTEM OPERATION

CHAPTER FIVE

• CONCLUSION
  • RECOMMENDATION
• REFERENCE

CHAPTER ONE

1.0                                                        INTRODUCTION

After the generation and distribution of electricity, if it is not well managed by the final consumer,there could be losses and serious problems to the loads and user alike. With the recent increase in the use of power in our homes and industries, there is the need to adequately protect our homes, industries and every other appliance that make use of electricity. Thus a phase failure detector is overly important both for the improvement of the quality of service from the power utility companies and the protection of life and properties of the electricity consumers.

1.1                                            THE CONCEPT OF THE STUDY

This is a situation where any of the three phases in a power system fails. This could be a result from a fuse blowing up or an interruption in the power line. Phase failure could be caused by any of the following:

a.Unbalanced voltage

b.Single phasing or phase loss

c.Overloads

d.Power outage (short cycling, over cycling)

e.Overvoltage

f.Under-voltage

g.Phase reversal (incorrect phase sequence)

The phase failure detector under consideration in this work is an electro-mechanical device used in power system engineering to protect a load from damage due to a failure in any of the phases supplying power to the load. It automatically cuts off the load from the supply if one of the individual phase conductors becomes faulty.

A phase failure detector is particularly important component in many assembly plants using the mains power supply. In such assemblies, the total loss of power in a phase of the mains supply or a significant reduction in its value due to uneven load conditions will cause serious problems.

Examples of other systems requiring phase failure detectors include power supplies for three-phase motors, transformers, and rectifiers. A more prominent example is the rectifier solutions in which a semi-controlled thyristor bridge is used. It is important that even short network breaks are detected to ensure that control of the bridge does not continue in diode mode once mains voltage has been restored. This is because intermediate circuit voltage can occur during an outage, resulting in fuses blowing when the power supply voltage is restored, and leading to a break in the operation of a process. Phase failure detector can thus be used in many different industrial applications, in ships,and in a national power supply network. They prevent damage to load if one of the individual phases is interrupted.

1.2                                             OBJECTIVE OF THE PROJECT

The main objective of this study is to construct a device for detecting  total loss of power in a three phase electrical network.  Phase failure detectors of this kind are used in multi-phase voltage-supply networks, to detect a loss of, or reduction in voltage in one or several phases.

1.3                                          APPLICATION OF THE PROJECT

Examples of systems requiring phase failure detectors include power supplies for three-phase motors, transformers, rectifiers, and network inverters. Particularly in rectifier solutions, in which a semi-controlled thyristor bridge is used, it is important that even short network breaks can be detected, to ensure that control of the bridge does not continue in diode mode once mains voltage has been restored. In such solutions, this is because intermediate circuit voltage can crash during an outage, resulting in fuses blowing when the power supply voltage is restored, leading to a break in the operation of a process. Phase failure detectors can thus be used in many different industrial applications, in ships, and in a national power supply network.

1.4                                 PROBLEM/LIMITATION OF THE PROJECT

The device does not detect a missing phase or a normal voltage outage in all phases. In addition, the solution operates so slowly that it is unsuitable for use, for example, in connection with modern frequency converters. The slowness is due to the electromechanical components.

1.5                                              PURPOSE OF THE PROJECT

The purpose of the work is to create a simple and inexpensive phase failure detector, which will not only detect a fault state, but also which of the phases is defective. The invention is based on the phase failure detector being equipped with a separate detector circuit for each phase being monitored. The detector circuits are connected between the phase being monitored and a common connection point, so that the common connection point forms a reference level.

1.6                                                 SCOPE OF THE PROJECT

The phase failure detector can then be incorporated in the equipment assembly and set to monitor the alternating voltage being fed to it. If the common connecting point of the detector circuits of the phase failure detector is connected to the reference potential leading from the direct-voltage circuit of the rectifier, for example, to the medium voltage of the direct-voltage circuit (the potential level in the middle of the minus and plus potentials), the phase failure detector will be able to detect each defective phase, independently of the operation of the other phases.