ABSTRACT

Insulation deterioration occurs on power system when insulators are subjected to abnormal stresses. Since insulators cannot resist indefinite amount of energy, with enough voltage applied, any insulating material will eventually succumb to the electrical pressure and electron flow will occur and once current is forced through an insulating material, breakdown of that material’s molecular structure has occurred. After breakdown, the material may or may not behave as insulator any more.

This project presents the construction of effective and efficient laboratory equipment designed to detect the breakdown of insulators when subjected to excess voltage and also to calculate the dielectric strength of insulators.

The equipment constructed incorporates a high frequency transformer to supply the different test voltages, a voltmeter to measure the applied voltage to the electrodes as well as the flashover voltage, a transistor to switch ON the high frequency transformer, a feedback circuit to maintain a stable voltage supply and an LED to indicate when a breakdown of insulators has occurred.

       Also, the position of the electrodes that is the distance between the two electrodes/conductors was also considered because it helps in the determination of the dielectric strength of the insulator.

       This work is split into five chapters thus: Chapter 1 deals with the general introduction of the work; Chapter 2 presents the review of the literature based on the previous information by other researchers and scholars. Chapter 3 deals with the function of the individual components of the equipment, the working principle as well as the circuit diagram. Chapter 4 deals with the main project design, testing, results and the observations while Chapter 5 presents the conclusion and the recommendations.

Chapter One

INTRODUCTION

Insulation is the isolation between conductors of electrical power system. It may be solid, liquid, gas or vacuum. The insulation deterioration and its effects are two phenomena that must be familiar with by any electrical or maintenance engineer if adequate safety of equipment and personnel and continous service to consumers are to be maintained.

Since the introduction of electricity in the 19th century, there has been a growing demand for electrical energy. Higher voltages led the researchers to develop new types of insulators. Many natural insulators, which were widely used at the beginning of this century, have been replaced by ceramic or porcelain materials. Many of these suffer from low impact strength, inflexibility, cracking during the manufacturing process, etc. A great variety of organic insulating materials are being used as electrical insulation in cables, machines, switch boards, outgoing lines and since these devices are being used under severe ambient conditions, breakdown of the insulating material has become a serious problem and it has a strong influence on safety and reliability of the insulators.

Deterioration of insulators occurs as a result of ageing and stresses imposed on them during their normal working life. The end result of the occurrence is the damaging or shortening of the life span of electrical equipment being protected by these insulators. Occasionally, personnel and environment in which such system is being operated are negatively affected. Also, the cost of replacement of the equipment is another effect that must not be over-looked.

This project deals with the determination of dielectric strength of insulators by investigating / determining the voltage that can breakdown a particular insulator. The result of this preliminary study on solid insulator show that every insulator has a particular voltage that it can withstand without breaking down that insulator’s molecular structure.

Generally, a survey of previous equipment used by the various researchers was found to be very complicated and expensive and such equipment cannot be afforded by local Nigerian researchers due to cost. It was this that necessitated us to come up with a locally made equipment to detect the breakdown of insulators due to excess voltage in practical system. The construction is simple, cheap and reliable.