Reliability Assessment of GSM Power System Network

ABSTRACT

This work presents the reliability assessment of the Power sub-system of the North West Region of Airtel network for a period of one year.

The Power model was found to be an integrated setup of major Power subcomponents such as transformer, automatic voltage regulator, generators, rectifier system, battery bank, and Power control systems such as  automatic  transfer switch and automatic main failure,

which are all interfaced in a definite topological structure, with unique redundancy model at each network site. The impact of critical power failure event at different hierarchical stations on the subscribers was also assessed.

The reliability data for power sub-system was collected to determine the reliability indices of the power equipment. The data were analysed using the MATLAB version 7.4 software.

The two-generator system at the integrated switch sites, integrated hub sites, terminal end sites and independent of PHCN power supply on the network exhibited relatively high reliability,

with fault tolerance by the prevalence of duty cycle availability indices of 51.83%, 56.00% and 56.5% respectively under a standard configuration of 50.00% duty cycle absolute availability index for a generator unit.

The rectifier system with modules of failure rate of 0.040/103h installed on the network was deduced to possess a high reliability index close to unity within a unit hour interval.

Empirical findings  show that the use of battery units with voltage rating of 3V, 6V and 12V on the network of -48V combinatorial battery bank system would yield relatively high reliability close to unity.

The study result showed that the efficiency of the network power system model depends on the degree of automation of the subcomponents and the degree of ambient condition changes.

It was concluded that the reliability standards of the GSM power sub-system are dynamic and depends on the redundancy mode of each subcomponents, the degree of redundancy,

the failure ratings or lifecycle and scalability of the subcomponents unit used in the system under optimal working conditions of all the subsystems and ideal maintenance practice.

TABLE OF CONTENTS

TITLE PAGE
TITLE PAGE – – – – – – – – – – i
DECLARATION- – – – – – – – – – ii
CERTIFICATION- – – – – – – – – – iii
DEDICATION- – – – – – – – – – iv
ACKNOWLEDGEMENT- – – – – – – – – v
ABSTRACT- – – – – – – – – – – vi
LIST OF FIGURES- – – – – – – – – – vii
LIST OF TABLES- – – – – – – – – – viii
LIST OF ABREVIATIONS- – – – – – – – – x
DEFINITION OF TERMINOLOGIES- – – – – – – xi
TABLE OF CONTENT- – – – – – – – – xii

CHAPTER ONE: INTRODUCTION

1.1 BACKGROUND INFORMATION– – – – – – – 1
1.2 THESIS OUTLINE- – – – – – – – – 1
1.3 THESIS MOTIVATION– – – – – – – – 3
1.4 PROBLEM FORMULATION- – – – – – – – 4
1.5 AIMS OF THE STUDY- – – – – – – – – 7
1.6 MOTIVES FOR THE AIMS- – – – – – – – 8

CHAPTER TWO: LITERATURE REVIEW AND THEORETICAL BACKGROUND- 9

2.1 INTRODUCTION- – – – – – – – – 9
2.2 LITERATURE REVIEW- – – – – – – – 9
2.3 STRUCTURE OF THE NETWORK- – – – – – – 11
2.4 MAJOR SUBCOMPONENT OF THE NETWORK POWER SYSTEM- – 15
2.4.1 Generator Subsystem- – – – – – – – 15
2.4.2 Rectifier Subsystem- – – – – – – – 16
2.4.3Automatic Voltage Regulator (AVR) Subsystem- – – – – 17
2.4.4 Battery Bank- – – – – – – – – 18
2.5 THE NETWORK POWER SYSTEM MODEL- – – – – – 18
2.6 REDUNDANCY TOPOLOGY OF POWER SUBSYSTEM ON THE MODEL- 20
2.6.1Redundancy Topology of Generator – – – – – – 20
2.6.2Redundancy Topology of Rectifier System– – – – – 22
2.6.3 Redundancy Topology of Battery Bank System- – – – – 22
2.7 CHARACTERISATION OF NETWORK POWER OUTAGE- – – – 25
2.7.1 Nature of Free and Forced Outage at a Network Site- – – – 25
2.7.2 Nature of Partial and Total Power Outage at a Network Site- – – 25
2.8 THE CRITICAL POWER RELIABILITY EPISODE- – – – – 26

CHAPTER THREE: METHODOLOGY

3.1 INTRODUCTION- – – – – – – – – 28
3.2 DATA COLLECTION TECHNIQUE- – – – – – – 29
3.3DESCRIPTION OF RELIABILITY DATA OF MAJOR POWER SUBCOMPONENTS – 30
3.3.1 Generator Reliability Data– – – – – – – 30
3.3.2 AVR Reliability Data- – – – – – – – 35
3.3.3 Rectifier System Reliability Data- – – – – – – 39
3.3.4 Battery Reliability Data- – – – – – – – 43
3.4 DATA EVALUATION TECHNIQUE- – – – – – – 46
3.5 DATA ANALYSIS- – – – – – – – – 47
3.5.1 Analysis of the Generator Reliability Data– – – – – 48
3.5.2 Analysis of the AVR Reliability Data– – – – – – 50
3.5.3 Analysis of the Rectifier Reliability Data- – – – – – 51
3.5.4 Analysis of the Battery Bank Reliability Data- – – – – 52

CHAPTER FOUR: RESULTS AND DISCUSSION

4.1 INTRODUCTION- – – — – – – – – 55
4.2 ASSESSMENT OF POWER SUBCOMPONENT RELIABILITY STANDARDS- 55
4.2.1 Assessment of the Generator Reliability Standards- – – – 55
4.2.2 Assessment of the Rectifier System Reliability Standards- – – – 57
4.2.3 Assessment of the Battery Bank Reliability Standards- – – – 61

4.3 CRITICAL EVENT ANALYSIS AT HIERARCHICAL STATION- – – 65

CHAPTER FIVE: SUMMARY, CONCLUSION AND RECOMMENDATION- – 70

5.1 INTRODUCTION- – – – – – – – – 70
5.2 LIMITATIONS- – – – – – – – – – 70
5.3 SUMMARY OF MAJOR FINDINGS- – – – – – – 71
5.4 CONCLUSION- – – – – – — – – – 72
5.5 RECOMMENDATIONS- – – – – – – – 72
REFERENCES- – – – – – — 74

INTRODUCTION

1.1 Background Information

Since the advent of global system for mobile communication (GSM) in Nigeria in 2001, the telecommunication industry has been experiencing unprecedented expansion in the number of subscribers.

However, this increase in the use of GSM network have put enormous pressure on the network operators to ensure reliability and quality of service desired by the customers, but the reality on ground is that many of the network operators have not achieved the desired results [1, 2].

Reliability and quality of service can be affected by either traffic congestion or network failure due to equipment malfunction.

Many studies have been carried out to ascertain the performance of GSM operators in Nigeria based on the size of traffic carried by the network operator and the causes of congestion in the network [3].

However, much attention has not been devoted in the past to network failure due to power outages caused by equipment failures. These outages affect the reliability and quality of service rendered by the network operator.

Hence, it is essential to determine the number of customers affected by these outages when such situations occur in order to establish the best methodology in the allocation of resources to minimise such occurrences.

REFERENCES

Shittu, W. A. (2006) Cellular Mobile Radio Propagation Characteristics: Case Study of Globacom and Mobile telecommunications networks (MTN). MSc Thesis. Ahmadu Bello University, Zaria. Retrieved March 21, 2008 from Department of Electrical Engineering Theses, Ahmadu Bello University, Zaria.
Saturday, E. R.(2006) Telephone Traffic Forecasting by Least Square Model (A Case Study of Nitel Northwest Zone, Kaduna). MSc Thesis. Ahmadu Bello University, Zaria. Retrieved March 21, 2008 from Department of Electrical Engineering Theses, Ahmadu Bello University, Zaria.
Ebong, E. J.(2006) Congestion Analysis (A Case Study of Nitel Network Ibadan Center).MSc Thesis. . Ahmadu Bello University, Zaria.  Retrieved March 21, 2008 from Department  of Electrical Engineering Theses, Ahmadu Bello University, Zaria
Mas’ud, A. (2006) Fault Management in Communication networks (A Case Study of the CDMA Intercullar network at Kaduna). MSc Thesis. Ahmadu Bello University, Zaria. Retrieved March 21, 2008 from Department of Electrical Engineering Theses, Ahmadu Bello University, Zaria.
Chen, Y. (2006) Episode Perspective of Wireless Network Dependability. MSc Thesis. Ohio University, Ohio.
Snow, A., Varshney U.and Malloy A., (July 14, 2000).Reliability and Survivability of Wireless and Mobile Networks IEEE Computer Magazine, pp. 49-55,

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