The Inadequacy Of Earthing In Building Structures In Zaria

The Inadequacy Of Earthing In Building Structures In Zaria

CHAPTER ONE

RESEARCH OBJECTIVES AND METHODOLOGY

Electricity and Electronics play a vital role in the life of everyone. Modern electronic systems, such as computers, radar and telecommunication equipment and/or installations are highly sensitive and susceptible to lightning and electrical surges and other transient pulses received through power or signal lines. Proper grounding and bonding through low impedance ground is essential to facilitate dissipation of these unwanted signals. The objectives of this study are, among others to:

i) Determine the extent of exposure of electrical and electronics gadgets in buildings and structures and their occupants within Zaria to the danger of direct hit by lightning strikes. The possible number of lightning strikes will also be determined;
Determine the earthing resistance of some buildings around Zaria and compare the measured earthing resistance to the standard specified earthing resistance; and
Determine the earthing resistance of Zaria NITEL exchange and compare the value obtained with the standard specified earthing resistance of the industry.

CHAPTER TWO

THEORETICAL BACKGROUND

EARTHING

An effective earthing system, which is a fundamental requirement of any modern structure or system, is indispensable for operational and/or safety reasons. Without such a system, the safety of the structure and its occupants as well as the equipment contained within it is compromised [7, 11, 12].

Earthing Systems typically fall into (but are not limited to) one of the following categories:

i) Lightning protection
ii) Electrostatically induced overvoltage of a charged cloud
Telecommunications.

A good earth connection should have:

i) Low electrical resistance to earth
ii) Good corrosion resistance

Ability to carry high currents repeatedly

i) A reliable life of at least 30 years [13, 14].

The crucial factors that determine the resistance to earth of an electrode are: i) Soil Resistivity: The following factors affect the soil resistivity: · Physical composition: Different soil compositions give different average resistivities as in Table 2.1 [13, 15].

CHAPTER THREE

METHODOLOGY

INTRODUCTION

This research is an empirical investigation of the effect of lightning strikes on buildings, structures and equipments within Zaria as a result of the type and quality of the earthing system. The earthing system is an essential element for the electrical system security and it is required to:

Allow for protective devices activation when there is an insulation fault; ii) Equalize the potential of conductive parts that can be accessed simultaneously, with the potential in the surrounding soil in order to prevent people from being exposed to hazardous voltages;
Allow the lightning strike energy to be safely dissipated; and iv) Reduce electromagnetic interferences [26].

The Institute of Electrical and Electronics Engineers Standard 142, Recommended Practice for Grounding of Industrial and Commercial Power Systems states: “The most elaborate grounding system that can be designed may prove to be inadequate unless the connection of the system to the earth is adequate and has a low resistance. It follows, therefore, that the earth connection is one of the most important parts of the whole grounding system. It is also the most difficult part to design and to obtain…”[27]. In general the earth resistance is defined as the resistance of the earth to the passage of electric current [27] but in practice, it is the resistance existing between the electrically accessible part of a buried electrode and another point of the earth, which is ‘far away’[26].

CHAPTER FOUR

RESULTS AND ANALYSIS

INTRODUCTION

This study investigated the effect of lightning strikes on people, buildings, communication towers and equipment by determining the number of lightning strikes on certain structures depending on the location and height of the structures and also the earthing resistances of some of the structures within Zaria.

The results obtained from these investigations are presented in this Chapter with the analysis and implications of the results.

CHAPTER FIVE

CONCLUSIONS AND SUGGESTIONS FOR FURTHER WORK 5.1 INTRODUCTION

The risks involved in failing to comprehensively address the issue of lightning and over voltage protection include the following:

∙ Physical damage to equipment resulting in replacement costs;

∙ Danger to residents or staff and other personnel from the effects of lightning discharges; and

∙ Partial or complete loss of operations and system downtime resulting in lost revenue.

This study determined the number of lightning strikes on certain structures depending on the location and height of the structures and also the earthing resistances of some of the structures within Zaria with a view to determining the consequence of poor earthing and lightning protection on the structures. It is worth noting that single lightning flash may be in order of 20-30kA, 200×10⁶V and will take place within 30 millionth of a second [17, 18] and this can cause catastrophic damages and even loss of lives if a proper protection system is not put in place

CONCLUSIONS

It can be concluded that most building contractors in Zaria do not adhere to standard building and electrical installation practices because non professionals are involved in the building construction, electrical earthing and lightning protection systems, there have been several reports of loss of properties due to the breakdown or absence of earthing and lightning protection systems.

LIMITATIONS

The Megger was the only instrument used in this study to take all measurements of the earth resistance. There was no alternative set of equipment so it was necessary to rely on the accuracy of the Megger for the accuracy of the measurement. And this point is critical because of the analogue nature of the Megger. It would have been preferable to have used more than one type of equipment in order to be able to establish the accuracy of the measurements obtained. This was not possible because there was no alternative equipment available.

REFERENCES

1) “Earthing Systems” (From Wikipedia, The Free Encyclopedia) http://en.wikipedia.org/wiki/Earthing_system.htm
2) “Lightning” (From Wikipedia, The Free Encyclopedia)
http://en.wikipedia.org/wiki/lightning.htm
3) Airport Authority of India [2006], “Lightning and Surge Protection and Earthing System of CNS Installations”, Communication, Navigation and Surveillance (CNS) Manual Vol. V, 1.ed., pp1-34.
4) Dzara, A.D. [2006], Determining The Soil Resistivity and Effective Earthing Resistance For The Nigerian Telecommunications Limited Digital Exchange, Mubi, Unpublished M.Sc Thesis, Department of Electrical Engineering, A.B.U. Zaria.
5) Krahe, C. [1998], “Lightning Strikes and Airbus Fly-By-Wire Aircraft” www.content.airbusworld.com/SITES/Customer_services/html/acrobat/fast_ 22_p24_27.pdf
6) RFI Pty [2004], “Earthing”
www.rfi-ind.com/au/download/earthing%20rev2%200700.pdf 7) Nweze, N. [1995], “Better Earthing (Grounding) Techniques” Nigerian Telecommunications Limited, Lagos. (Unpublished Report).
8) Nigerian Telecommunication Limited, [1995], “Draft Specification 0001, Earthing Systems for Telecommunications Plants”.
9) Conroy, M. D., and Richard, P. G. [2002], “Deep Earth Grounding”, Computer Power and Consulting.
www.cpccorp.com/deep.htm
10) Schmitt, H. and Winter, W. [2000], “Simulation of Lightning Over-Voltages in Electrical Power Systems”
www.ipst.org/TechPapers/2001/IPST01Paper030.pdf
11) Siemens AG [2006], “Earthing”
www.industry.siemens.com/Water/en/solutions/infrastructure_earthing.html

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