life cycle management for power transformers used in the eskom distribution network

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Gf-t it-

LIFE CYCLE MANAGEMENT FOR POWER

TRANSFORMERS USED INTHE ESKOM DISTRIBUTION

NETWORK-CASE STUDY.

By

SARAH REFILWE MPHO CHILWANE

920202933

A DISSERTATION SUBMITTED IN PARTIAL

FULFILMENT OF THE REQUIREMENTS FOR THE

DEGREE

MAGISTER INGENERIAE

IN

ENGINEERING MANAGEMENT

IN THE

FACULTY OF ENGINEERING

AT THE

UNIVERSITY OF JOHANNESBURG

February 2011

SUPERVISOR: PROF.JHC PRETORIUS

CO SUPERVISOR: DR OJ KRUGER

Page i

ABSTRACT

Title:

Author:

Supervisor:

Co-Supervisor:

Degree:

Keywords:

Life cycle management for power transformers used in the

Eskom Distributionnetwork - casestudy.

Sarah Refilwe Mpho Chilwane

Prof. JHC Pretorius

Dr. DJ Kruger

Master in Engineering Management

life cycle, asset, risk, transformer, reliability, condition

monitoring.

Electricity is a crucial key component in every day life influencing the economy,

safety; health, productivity and comfort just to name a few. The benefits and

importance of electricity can be easily taken for granted by the consumer.

Towards the end of 2007, South Africa suffered numerous power outages and that

lead to the implementation of load shedding byEskom, the electricity utility in South

Africa, in order to manage the shortage ofelectricity [1].

Electricity utilities constantly make decisions that affect the cost, reliability and

quality of their services. Therefore engineering designs and maintenance strategies

should be updated frequently. The benefits ofthese updates to the system would have

a significant performance improvement inregards to reliability and the quality of the

electricity. The outline of asset management is therefore to focus on the business

assets so thatthe organisation could serve the customers effectively.

As a result, the focus for the research is to develop a life cycle management plan for

one of the main assets utilised in the distribution networknamely power transformers.

The researchwould include a study of power transformers and customs that could be

used to improve the reliability, logistics, safety and the capital investments of the

network.

Page ii

Power transformers are static equipment, and failure rate is very low compared to

other assets found in substations. As a result of their sizes, transformers requires

more time and special arrangements should a failure occur. A risk and condition

analysis was conducted on transformers and the results and conclusions were

discussed.

Page iii

ACKNOWLEDGEMENT

There are many people who have supported and encouraged me during this project

investigation. This meant a lot to me and I am very grateful. I would like to take this

opportunity to acknowledge the following peoples for their various contributions to this

thesis.

First I would like to thank my study leaderProf. Jan-Harm C Pretorius and my mentor

James Motladile for their patience and the time spent in assisting me with this project.

My parents have supported me from pre-school till today andhave inspired me in my

studies; I thank you very much for everything. To my sisters Paballo and Pontsho,

thank you for your support, and the cups of coffee you havemade mewhilst I was busy

with the document and the dance lesson when I was taking a break.

I would like to give a special thanks to my friends.

Finally, I am grateful to my husband Mzwandile Buthelezi, who in many ways has

contributed to myproject, discussing research with me, and taking care of me when the

project demanded all my time.

Pageiv

DECLARATION

It SARAH CHILWANE hereby declare that all work presented within this report is

solely my work and that any research as well as information obtained from outside

sources have been referenced to the best ofmy abilities.

Sarah Chilwane

October 2010

Page v

TABLE OFCONTENTS

ABSTRACT 11

ACKNOWLEDGEMENT IV

DECLARATION V

NOMENCLATURE X

CHAPTER 1- RESEARCH BACKGROUND AND PROPOSAL•• 1

1.1 PROJECT BACKGROUND 1

1.2 AIM 1

1.3 OBJECTIVES 2

1.4 RESEARCH METHODOLOGy 2

1.5 OVERVIEW OF DISSERTATION 2

1.6 CONCLUSION 3

CHAPTER 2-INTRODUCTION 4

2.1 INTRODUCTION 4

2.2 DIVISIONS INTHE UTILITY 4

2.3 LIFE CYCLE MANAGEMENT PLAN 10

2.4 ASSETS MANAGEMENT 12

2.5 LITERATURE SURVEy 13

2.6 SCOPE OF WORK 15

2.7 CONCLUSION 15

CHAPTER 3- CONCEPTUAL PHASE 163.1 INTRODUCTION..................... 16

3.2 DISTRIBUTION ENGINEERING 16

3.3 THE ELECTRICITY UTILITY'S APPROACH ON LIFE CYCLE

MANAGEMENT 23

3.4 LIFECYCLE MANAGEMENT PLAN (LeMP) STANDARDS 25

3.5 THE ASSET MANAGEMENTSYSTEM 27

3.6 ASSET MANAGEMENT PROGRAMME 28

Page vi

3.7 CONCLUSION 30

CHAPTER4- CASE STUDY - POWER TRANSFORMERS 31

4.1 INTRODUCTION 31

4.2 THE RECOMMENDED LIFE CYCLE MANAGEMENT OF POWER

TRANSFORMERS 31

4.3 ASSET RISK METHODOLOGy 39

4.4 CONCLUSION 43

CHAPTER5- CONCLUSION 44

5.1 INTRODUCTION 44

5.2 GENERAL CONCLUSION 44

5.3 PROPOSED FURTHER WORK 45

APPENDIX A: CENTRAL REGION MAP 47

APPENDIX B: POWER TRANSFORMER FMEA 48

REFERENCES 68

Page vii

TABLE OF FIGURES

Figure 1:Thedistribution process of electricity [6] 5

Figure 2: Evolution ofSouth Africa's energy supply from 1971 to 2007 [9] 6

Figure 3: Eskom Transmission station 7

Figure 4: Servitude required for transmission lines [11 ] 8

Figure 5: Pole mounted distribution transformer 9

Figure 6: Lifecycle phases of process asset system [16] 10

Figure 7: Loop diagram showing the relationship between elements of a

system [17] 11

Figure 8: Ideal power quality at 1.0 p.u and 50 Hz sinusoidal voltage [33] 17

Figure 9: Real power quality, the distorted voltage waveform [33] 17

Figure 10: Value chains utilised in Eskom Distribution [5] 19

Figure 11: Current distribution initiatives that relate to asset management [4].

.......................................................................................................................22

Figure 12: Integration of project, asset and product life cycles [43] 23

Figure 13: Life cycle management of electricity in Eskom [44] 24

Figure 14: Contribution of functions in an organisation [29] 25

Figure 15: Levels of assetsand theirmanagement [32] 27

Figure 16: Asset lifecycle framework [47] 28

Figure 17: The decision support mechanism of life cycle engineering [51] 32

Figure 18: Active part of a transformer 33

Figure 19: The Bathtub Curve [56] 36

Figure 20: Asset risk management model [4] [57] 39

Figure 21: Model used to calculate asset risk [4] .40

Page viii

LIST OF TABLES

Table 1: Eskom Distribution asset management programme [2] [49] 30

Table 2: Transformer risk analysis 34

Table 3: Failure Mode effect and analysis for powertransformers 35

Table 4: Preventive maintenance plan for transformers 37

Table 5: Assessing the risks associated with operation and maintenance of an

asset [4) [59) 41

Table 6: Operational and Maintenance Risk Contribution [4] [55] 42

Table 7: Environmental factors included in the Risk Model [4) [55] [59] 42

Page ix

NOMENCLATURE

AC

BSI

CAPEX

FMEA

HV

Hz

IBR

IEEE

ISO

IP

IT

Ian

KPI

LCA

LCI

LCIA

LCMP

LCM

LPU

LV

MN

MADS

MRC

MV

MW

NAC

NERSA

NDP

OPEX

PAS

alternating current

British Standards Institution

capital expenditure

failure mode effect andanalysis

high voltage

hertz

incentive-based regulation

Institute of Electrical and Electronics Engineers

International Organisation for Standardisation

intellectual property

information technology

kilometre

Key Performance Index

life cycle assessment

life cycle inventory

lifecycle impact analysis

life cycle management plan

life cycle management

large power users

low voltage

maintain network

manage availability of supply

manage revenue cycle

medium voltage

megawatt

network asset creation

National Energy Regulator of South Africa.

network development plan

operational expenditure

Publicly Available Specification

Page x

PHI

pu

SPU

SAlOl

SAIFI

SMS

USPTO

WIPO

ZAR

Ac

ARV

AR

P

Afr

OMfr

Enfr

plant health index

perunit

small power users

system average interruption duration index

system average interruption frequency index

short message sending

United States Patent and Trademark Office

World Intellectual Property Organisation

South African Rand

Asset criticality

Asset replacement value

Asset risk

Probability of asset failure

Asset failure rate

Operation and maintenance failure rate

Environmental factors failure rate

Page xi

Chapter J: Research background and proposal

CHAPTER 1- RESEARCH BACKGROUND AND PROPOSAL

1.1 PROJECT BACKGROUND

Eskom is oneofthe ten largest electricity providers in the world [I]. The major objectives of

the utility are to generate, transmit and distribute electricityto consumers in South Africa and

certain neighbouring countries [2].

The utility has three major divisions namely Generation, Transmission and Distribution.

These divisions consist of entities such as power generating substations, power lines,

substations, mini-substations and other equipments used during the generation of power [3].

The equipment and the different divisions involved at the electricity utility makes it an asset

centric organisation. If a transformer or any other equipment in the electricity delivery

network fails then the customers supplied from that equipment will be affected by that

failure. As a result, assets used in the business ofelectricitysupply, should be maintained and

monitored consistently.

Electricity distribution networks have primary and secondary substations. Primary

substations deliver energy to secondary substation and the secondary substations have the

responsibility of delivering that energy in a safe, measurable and sustainable manner.

Through thisprocess the end-userwill receive operable energy.

1.2 AIM

This dissertation aims toconduct research on power transformers within Eskom Distribution

inthe central region (see Appendix A for region map). The desired outcomes are to develop

a structured plan for the region and introduce a life cycle management plan for power

transformers. As well as to develop a procedure that could improve the reliability,

performance andmaintenance of power transformers used in Eskom's distribution networks.

Page I

Chapter 1: Research background and proposal

1.3 OBJECTIVES

• To provide a process by which the applicable transformer's life cycle plans wouldbe

compiled, reviewed and managed.

• To determine a detailed and measurable level of performance or condition required of

the transformers.

• To analyse risk methodologies that can be applied to transformers in the process of

developing their asset management plans.

1.4 RESEARCH METHODOLOGY

In this section a list of procedures used in the research are presented. These procedures are

important in determining thesuccess of thestudy:

a) A generalised study was developed to highlight the value chains used in the

organisation.

b) A detailed risk assessment for power transformers was developed. The results

thereof give a guideline of the management for power transformers [4].

c) The information acquired from the value chains provide an understanding on

how the different departments relate to each other. It also highlights how the

organisation incorporates life cycle management [5].

d) A case study on one of the power transformers used In the utility was

performed. This case study illustrates the practical application of the risk

assessment methodology.

1.5 OVERVIEW OF DISSERTAnON

Chapter 1 is an introduction to the information contained in this document and an overview

on the importance of life cycle management and asset management. It contains a brief

description of the departments found in theelectricity utility. The objective and goals of the

dissertation are also discussed.

Page 2

Chapter J: Research background and proposal

Chapter 2 forms the conceptual phase of this dissertation. It provides a description of

Eskom's distribution departments and the value chains involved in the management of the

network. It provides an overview of the importance of life cycle management and asset

management in Eskom Distribution.

Chapter 3 is the implementation phase if the research. It provides a thorough investigation

and plan for asset management of power transformers used in Eskom Distribution. It outlines

the different stages involved in asset management and the asset management strategies

namely maintenance, refurbishment and network strengthening.

Chapter 4 provides a discussion and final conclusion to this dissertation. Within this chapter

the objectives of this dissertation as well as the shortcomings will be discussed. Before final

conclusion recommendations for further work required willbe discussed.

1.6 CONCLUSION

This chapter forms part of the research proposal for this study. A work plan on how the

research will be conducted is developed and tabulated. Chapter I provides the project

background and research objectives of thisstudy. During the execution of the work plan the

research methodology will be implemented.

As part of the research proposal, the issues tobe addressed arealso listed. Chapter I provides

information thatjustifies the requirement toconduct this study. Assumptions have to be made

and contingency have to be in place in the event that the research does not follow what is

specified in thework plan. The following chapter is the introduction ofthis dissertation.

Page3

Chapter2: Introduction

CHAPTER 2 - INTRODUCTION

2.1 INTRODUCTION

Eskom was established on 151 of March 1923. The South African public and industry

consumes 95% of the electricity that is generated by Eskom. Theutility is the largest

producer of electricity in Africa and is the eleventh largest in the world in terms of

generation capacity [3].

The client in this case is Eskom Distribution, which has a distribution network of

320,035 kilometres of line and 3.6 million customers, including major wholesale

customers in municipalities, aluminium smelters and railways.

The three main divisions in utility (Generation, Transmission and Distribution) are

responsible for electricity delivery to the end user would be discussed briefly in the

following section.

2.2 DIVISIONS IN THE UTILITY

There are many different ways to generate electricity using natural resources such as

coal, oil, gas, hydroelectric, nuclear, geothermal, solar, andwind. The delivery of this

electricity to the consumer is one of the key components in the business that is

complicated and sensitive.

Page 4

generated at it is

relevant customers,

p!pf'tl"1i{'ih, is supelted to consumer 1S illustrated

RIltICUIlitlon LVLk1IlII(3l1tl~2211V)

L

DISTRIBUTION(132-33 kV)

lklr-.Comwlltion

1:The distribution process [6],

A brief explanation of key

in I will beexplained

2.2.1. GENERATIONSrsTEM

in the electricitydelivery system that

the following sections.

electrical generation £1""811011 is one of

In total

"""rtf"::""t""", to

stations throughout the {'""nt'Mt' are

an

installed C~lpaCJlty that exceeds Electricity is generated

use nt' ...."l",,,, .. technolcgv

s

illustrates South can see a Ilfowirlll

I I till

South Africa's historical energy supply

400

200

200

1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007

Veal1l• Cl>lll • Oil IIIGl!ll\l l:l ttu:hIat I tl{dro III CorriH_ &w IlIlte • Geoll1!!rmllllllotllrlwlnd

Figure 2: Evolution of South Africa's energysupplyfrom 1971 to2007 [9].

In South the utility produces over 000 MW of electricity to meet the

current demand andthis growing annually [7]. Therefore, for that reason, the

utility uses over 1000 tonnes of low quality coal in the production some of the

lowest-costindustrial in theworld [2].

generated electricity will transported for long distances

from the generation substation. The complex transmission system

IS explained inthe fi)ll.nwinc7 section.

at stations to

voltaze reduced to at 11 means

6

400

[10]

are

is

at

over a

3 illustrates a transrnission stations. A transmtssion

andmaintenance.

covers

Figure 3: Eskom Transmission station,

<:lpl"lIitncip<:l rlPlruu'fm,pnf within are responsible

coverage areasome

next. 2

to

up toa maximum

one station to

7

Chapter 2: Introduction

The transmission lines in the ce ntral region transport approximately 22 percent of the

total electricity supply in outh Africa (7]. Figure 4 illustrate servitude needed for

transmission lines.

Figure 4 : Servitude required for tran smi ssion lines [ I I].

Servitude is a registered right that a person has over the immovable property of

another [12]. This means that Eskom has the right to install structures or equ ipment

within its registered servitude.

2.2.3. D ISTRlIW TlON SYSTEM

Eskorn Distribution division w ithin Eskorn 's business has the re ponsibilit y to deliver

electricity erv ices, maintaini ng the distribution network and ensuring e ll toni er

satisfaction. Thc distribution sys tem cons ists of a distribution substation, distribution

lines. reticulation lines and crv icc connection as illustrated in Figure I

Page 8

on to an overhead

5: Pole mounted distribution transformer.

are different

distribution svsrern is

It incorporates equipment to nrevent or to

9

Aceordinz to

IS "mltel111ed to nr(\111111f' an ettective tons-term

to

an

are a

conception to retirement or disposat [14]. Itaddresses

maintenance (nreventative or corrective) replacement, or redesign a

nrovtdes an orgamsanon a concept

or irnnroved sustainability adopting this concept an organisation can improve on

,"","nt'p< OI [13] [15],

asset [16], It an assets

to retirement or

AC1QUlisition phase Uliliisalion phase


2.3.1. LIFE CYCLE COST

A part of life cycle management is based on the cost associated with asset life cycle.

G.1. Thuesen, W.J. Fabrycky, defines life cycle cost as "all costs, both nonrecurring

and recurring, that occur over the life cycle" [16].

Life cycle cost should be analysed early in the planning, design and development of

an assets. This will ensure that the lifecycle cost in the operational phase is low. The

network condition will degrade over time; this will affect the network performance

which leads to the investments of the organisations. These investments can either be

capital expenditure (CAPEX) or operational expenditure(OPEX). Figure 7 illustrates

the relationship between elements of a network system [17].

(P.~~~Network

/': Condition"'" Internal( , Performance

Ageing CAPEX ~Target

Factoll 1Time

Investment

Re~.ources~) ~R1 Revenue ............. /'I ~ / v > customers

OPEX~ Demand

Customers

Distribution network operatorNotationB=Balancing FeedbackR=Reinforcing Feedback

Figure 7: Loop diagramshowing the relationship between elements ofasystem [17].

The contributing factors that determine the condition of a network are CAPEX for

acquiring power transformers, resources required for maintenance and in-service

operation of transformers. OPEX is used for reinforcing the network and to maintain

the condition ofpower transformers,

Page 11


2.3.2. IMPORTANCE OF A LIFE CYCLE MANAGEMENT PLAN

Electricity utilities, like Eskom, utilise lifecycle management to integrate operations,

maintenance, engineering, regulatory, environmental and economic planning

activities. This is done in a manner that manages aging, obsolescence and

preventative maintenance of the system.

Life cycle management planning provides an effective long-term planning tool. This

can be used to minimise unplanned capability loss, optimises operating life, and

maximises the returnof investment while maintaining network safety[18].

2.4 ASSETS MANAGEMENT

The formal definition of asset management from Publicity Available Specification

(PAS) 55 is: "Systematic and coordinated activities and practices through which an

organisation optimally manages its assets, and their associated performance, risk and

expenditures over their lifecycle for the purpose of achieving its organisational

strategic plan" [19] [32]. PAS 55 will be explained in detail in the following chapter.

An asset management plan (AMP) is a tactical plan that is used in an organisation to

manage its infrastructure and assets. AMP is put in place to ensure that services

rendered are at an acceptable quality and regulating standards. This plan is most

effective where a number of assets are co-dependant and must work together to

deliver a service[15].

Page 12


2.4.1 IMPORTANCE OFAN ASSETMANAGEMENT PLAN

It is important to note that an asset centric organisation should understand and

implement the asset management principles. By implementing these principles the

organisation will receive long term benefits. In Eskom Distribution an asset

management plan will provide measures to sustain the supply of electricity. To

further understand the topic of asset management, the following definitions will be

stated:

Asset: Physical, immovable substation equipment or infrastructure that forms part of

an electricity utility. Allocation of high voltage (HV), medium voltage (MV) and low

voltage (LV) networks, and that has a direct impact on the life cycle of the power

network [20].

An asset management plan is a tool that will provide the utility with information

regarding stock that they posses [21]. In the event of long-lead material failure, the

utility will have information about the time schedule and the location of replacement

equipment. With an asset management plan in place, the duration of outages will be

minimised.

2.5 LITERATURE SURVEY

World wide there have been efforts made by utilities to manage assets that are an

important component in the electricity delivery system [22]. In this section of this

dissertation aninvestigation is conducted to determine existing lifecycle management

of power transformers.

In utilities the reliability and functionality of power transformers under load has great

importance, therefore the asset management of power transformers is crucial [22]

[23]. The life cyclemanagement of utilitytransformer asset is nota new concept and

has been previously done by other utilitiessuch as in the United States.

Page 13


An intellectual property (IP) search for power transformer management was

conducted using the United States Patent and Trademark Office (www.USPTo.gov)

World Intellectual Property Organisation (www. W/po.int) and free patents online

(wwH'.{i-eepofen,wn!il/e.('om), Prior art was found relating to power transformers,

design specifications, transformer ratings and power transformer management. With

regards to life cycle management of a utility's power transformers, no art was found.

A search was conducted on the following peer reviewed electronic-resources for "life

cycle management of power transformers" for any publications, journals, magazines

and standards:

• IEEE (Institute of Electrical and Electronics Engineers) Xplore Digital

Library[22] [24] [25] [26],

• ScienceDirect search engine [27],

• Googlescholar [19] [28].

"Power transformer critical diagnostics for reliability and life extension" was one

result that was found from the search conducted. The other result found from the

search was "Power transformer condition monitoring and life-cycle management"

which provides earlydetection measures to manage the risk of developing failure for

power transformers.

The same search was conducted on Eskom's intranet database for "life cycle

management of power transformers" within Eskom Holdings Ltd Pty. It was found

that there was previously an intension to research into the implementation of an asset

management plan for transformers but this did not materialise. The performance and

reliability of power transformers can be increased by establishing management

strategies [23].

The introduction of a life cycle management plan in Eskom for power transformers

will reduce unplanned outages as well as catastrophic transformer failures. This asset

management plan will be uniquely for the South Africa market due to electricity

supply shortages andthe high amount of illegal connections [29].

Page 14


2.6 SCOPE OFWORK

This dissertation will only focus on the management of power transformers used in

distribution substations for central region. It will analyse the value chains used in the

engineering section of the utility and study the life cycle management approach that

electricity utilitiesmayfollow.

The asset management plan for power transformers will include a riskassessment and

a failure mode analysis of the transformers. Once the reliability studies are

conducted, a transformer maintenance planwill be developed.

2.7 CONCLUSION

In this chapter an overview of Eskom Holdings Ltd. was provided. The background

into the different departments found in Eskom Holding and their functions were

discussed. The importance of life cycle management plan and the definition of asset

management werediscussed briefly.

In the following chapter the conceptual phase of this study will be conducted.

Chapter 2 will investigate how the value chains in the electricity utility relate and

illustrate how life cycle management plan increases the reliability, availability,

quality, and safety the network.

Page 15

Chapter3: Conceptual Phase

CHAPTER 3- CONCEPTUAL PHASE

3.1 INTRODUCTION

In the previous chapter, explanations of thedepartments found in the electricity utility

as well as their impacts on the organisation were explained. The importance of life

cycle management for power transformers and the value chains used in the

organisation will be discussed in this chapter.

3.2 DISTRIBUTION ENGINEERING

The final step of the electricity utility is the distribution of electricity to the end-user.

This part of the network consists of power lines, substations,

mini-substations, andtransformers, Equipment failure withinthe distribution network

will result in poweroutages thereby negatively impacting the customers and affecting

the quality of supply.

The capability of a network to deliver the prescribed quality of uninterrupted power to

its customers is known as power system reliability. The standardelectricity reliability

indices that are used in a distribution network for maintenance and reliability of

equipments are [30] [31] [32]:

a) SAIDI (system average interruption duration index) whichis used to indicate

the duration over which the incidents or fault lasted in a particular feeder.

b) SAIFI (system average intenuption frequency index)which is used to indicate

how many time the system experienced faults.

These indices can have a negative impact in the management of the organisation's

asset if it is not regularly monitored. The frequency of asset failure implies that assets

are not maintained as required.

Page 16


Quality of supply is the level to which electrical supply to a customer's facility

conforms to the requirements of the service [33]. Poor quality includes factors such

as voltage drops, power surges and deviations from ideal sinusoidal waveform.

Figure 8 illustrates the ideal power quality that an electricity utility aims to achieve.

Figure 8: Ideal power quality at 1.0 p.u and 50 Hz sinusoidal voltage [33].

Figure 9 represents the real power quality waveform; real power quality waveform

represents the actual reading on the power instrument. It includes distortion, noise

which is due to the influences that are experienced.

Figure 9: Real power quality, the distortedvoltage waveform [33].

The frequency is another factor that is affecting the quality of supply. The frequency

of Eskom's generators are synchronised to the national grid at a frequency of 50Hz.

Since electricity is generated and transmitted as AC (alternating current), monitoring

of the frequency provides information with regards the electricity demand from the

network. If the electricity demand decreases the frequency will increase and when the

demand increases the frequency will decrease.

Page 17

Chapted: Conceptua IPhase

Technical parameters of power quality are as follows:

a) Voltage regulation,

b) Voltage unbalance,

c) Voltage dips,

d) Voltage harmonics,

e) Voltage flicker,

f) System disturbances.

In a deregulated environment, electrical utilities are underconstant pressure to reduce

operating costs, improve on equipment availability, improve on electricity quality

received by customers and reduce carbon dioxide emissions [34]. The following is a

discussion on specific standards that regulate utilities on the quality of its supply.

Minimum standards

Certain aspects of power quality, such as voltage waveform quality, are managed

from a regulatory point of view by minimum standards, for example, low voltage

magnitude must bebetween90% and 110% of nominal voltage [35].

Minimum standards are appropriate in regulating these aspects as customerappliances

are designed to work within these limits, and there is little or no benefit in meeting

stricter standards. Yet minimum standards are not appropriate in regulating continuity

of supply performance as there is no incentive for a utility to improve performance in

networks where minimum standards arealready being met[35].

Incentive-Based Regulation (IBR)

Under IBR (incentive-based regulation) schemes utilities are financially rewarded or

penalised based on a change in performance level [35]. Improved performance

(typically based on the average total outage time experienced by customers) can, for

example, be rewarded by an allowed increase in tariff [36]. Reduced performance

would result in anassociated reduction in tariff, in otherwords, less revenue [35].

Page 18


The first IBR scheme in South Africa was initiated by the National Energy Regulator

of South Africa (NERSA) for a 3 year(2006 -2009) multi year price determination for

Eskom Distribution [35]. This incentive scheme is focused on short term

improvements in reliability via OPEX (operational expenditure) activities such as live

line, maintenance and vegetation management [35] [37].

The performance of a network is mainly determined via the design characteristics of

the network like lengths of feeders, number of customers supplied per feeder, inter

connectivity between feeders and redundancy of equipment. These structural issues

are influenced by CAPEX (capital expenditure) investment decisions. A well

maintained and operated network canonly perform as well as is dictated by its design

characteristics [35].

Currently

3.2.1. VALUE CHAINS IN A DISTRIBUTION NETWORK

Eskom Distribution has strategies in place to achieve its primary objectives. These

strategies include organisational structures of the business. These structures are in the

form of value chains [38]. Figure 10 illustrates the value chains that apply in the life

cycle of the distribution network and its assets that are presently implemented in

Eskom Distribution.

!,IAN)

Optimiseh

custrmer }- Manage hInteranm Revenue }I Cycle

(OCI)

I I (MIlC)

I IJ II Manage Direct opnmree h

f1'l ) ____ -.J ustomer prqjeet Customer }:.......... -( leetrlncatlon Inn Interaction

(OCI)

~~C) (IUOS)

Figure 10: Value chainsutilised in Eskom Distribution (5).

Page 19


3.2.1.1. Developand marketproductservices

Understanding the South African market is the initial partof this value chain. This

market involves internal, external, stakeholders, customers and the macro

environment. Once the investigation and forecasting into the market has been

completed; a marketing strategy can be developed to achieve ongoing business

sustainability, growth and profitability.

3.2.1.2. Manage availability ofsupply

This value chain focuses on the network management; it ensures the real time

management and control of the supply and demand for electricity is performed. The

processes involved innetwork management include [39]:

a) Managing network performance,

b) Managing planned and unplanned work,

c) Escalation ofabnormal situations

3.2.1.3. Manage revenue cycle

The management of revenue cycle covers the life cycle ofconvectional and prepaid

meters, from the time the meter is received from the supplier to the time it is

discarded. This includes quantifying the electricity usage and identifying customers

which are large power users (LPU) or small power users (SPU) then the billing

process can be conducted [40].

3.2.1.4. Network asset creation

The network asset creating is the planning process withinthe network distribution. A

network development plan (NDP) is generated by the network planning department.

It provides a guideline for defining the study area and theobjectives of the planning

study. The following take place in theengineering domain oftheutility [41]:

a) Network asset creation

b) Maintain network

c) Manage availability of supply

Page 20

Chapters: Conceptual Phase

The other departments that also participate in this process by providing valuable

inputs relating to their scope of work are as follows [41]:

a) Substation department focusing onthe primarysubstation refurbishment and

performance of the network.

b) Land and development department deals with all the environmental and

servitude acquisitions.

c) Electricity delivery departmentfocuses on the operational issues and control

substation refurbishment.

d) Finance department provides an understanding of the various economic

structures, financial data andindicators.

e) Project engineering department designs the proposed plans issued by the

planning department.

"Asset risk management should be incorporated and integrated into the value chains

and business processes so that it can inform asset replacement, refurbishment and

maintenance decision making" [4]. Figure lIon the following page, shows a high

level summary of Eskom Distribution current initiatives related to Asset

Management [4].

Page 21

THE

opPclrtunJlty to lderatlty

to

it requires product understlmdmg,

It

management is quahtative,

is

operational processes are consistent

resources, information

a

12: Illlegrallioll ofrsroiect.

replacernent or recessgn

13 represents

Figure 13: Life management ofelectricity inEskom

natural raw

as

are burnt raw materials

raw m:lt~riz:ll"

is tollow'ed

to a;erlera:te, transmu

or recoverv

in

become a

all QI\IISIOlllS in an organtaation is

different departments contribute to

.'fgure 14: Contributionoffunetions in an orgimis811ion

3.4 LIFECYCLE M)~NALGEME1ST PLAN (LCMP) STANDARDS

silIndartis set

ensures

standards accustom to,

are

Chapters: ConceptuaIPhase

a) ISO 14040 - Life cycle assessment; Principles and framework (2006),

ISO 14040:2006 describes the principles and framework for life cycle

assessment (LCA) including: definition of the goal and scope of the LCA,

the life cycle inventory analysis (LCI) phase, the life cycle impact

assessment (LCIA) phase, the life cycle interpretation phase, reporting and

critical review of the LCA, limitations of the LCA, the relationship between

the LCA phases, and conditions for use of value choices and optional

elements.

ISO 14040:2006 covers life cycle assessment (LCA) studies and life cycle

inventory (LCI) studies. It doesnot describe the LCA technique in detail, nor

does it specify methodologies for the individual phases of the LCA.

The intended application of LCA or LCI results is considered during

definition of the goal and scope, but the application itself is outside the scope

ofthis International Standard.

b) ISO 14044 - Life cycle assessment; Requirements and guidelines (2006),

ISO 14044:2006 specifies requirements and provides guidelines for life

cycle assessment (LeA) including: definition of the goal and scope of the

LCA, the life cycle inventory analysis (LCI) phase, the life cycle impact

assessment (LCIA) phase, the life cycle interpretation phase, reporting and

critical review of the LCA, limitations of the LCA, relationship between the

LeA phases, and conditions foruse of value choices and optional elements.

ISO 14044:2006 covers life cycle assessment (LCA) studies and life cycle

inventory (LCI) studies.

Page26

THE

integrated asset management is imnortant

are different

asset

in

orgamsanons in

assets can

15 can

from or strategic, nhvsieal

asset managementassets.

an organisational strategic

is designed to support

and in tum aiming to meet a

in

is prmnanly assessled is

3.6 MA,NAGEME:NT PROGRAMME

managemen; is an nnnortant

readiness asset slablllly, therefore reducing

management IS considered as

a can

are mamteaance, rc:tllIbtsllme~111

Chapter3:Conceptual Phase

Maintenance is the basis for monitoring and realising the assets useful life. It

involves the re-installation of substation equipment to its intended condition and

performance through corrective or preventative actions [24] [48].

Refurbishment refers to the replacement of equipment in compliance with current

technical practices and desired operating performance. In substations for instance, it

will either be realised or extended in order to enhance the supply and the quality

thereof [24].

Strengthening is also known as re-engineering. It refers to the expansion or

upgrading of the substation and network to improve the capacity and the quality of

supply to the existing customer [24].

The utility classifies it assets as either primary or secondarynetwork assets. Network

reliability can be guaranteed when both the assets (primary and secondary) are

functional.

Primary substation assets comprises of overhead lines, power or instrumental

transformers, high or low voltage switchgear and cables. Most of the primary

substation assets are outdoor equipments and therefore needto operate under extreme

weather conditions and operate effectivelyand efficiently. Theseassets are the direct

energy delivery equipment and their failure will often lead to a disruption of the

network.

Secondary substation assets include the telecommunication, powersystems protection

relays, metering and control infrastructure. These are mainly indoor equipment and

are responsible for functionalities such as retrieving data from the network for billing

purposes.

Page 29

Chapterl : Conceptual Phase

The utility's existing structure does not support asset management and has a poor

integration between its plann ing and refurbishment sectors. There is a requirement for

a formal risk management struc ture and specialised skills and resources. It can be

concluded that asset management is a systematic process to effectively manage cost,

opera tions, maintenance of assets.

Ta ble 1 illustrates the phases involved in asse t management programme and the

implementation of asset management in Eskom Distribution. It assists in identifying

the gaps between PAS 55 and what is done at Eskom. PAS 55 is the Pub licly

Available Specification publ ished by the Briti sh Standards Institution for asset

management [32].

Table t: Eskom Distribut ion asset management programme (2) (49].

Asses ment DeslltD Pilot Implementation PhasePhase I Phase (( Phase III IVAssessment of Eskom Ox

Recommendation Solutions Pilot Implementatlen Full Rolloutvs,

for Ide ntified gaps of Asset Managem~ntImpl ementa tion of Alld

PAS 55 Manal!ementGaps identified: • Refocus Dx 10 be an asse t • Pilot improved • Roll out improved

• No AM Policy andStrategy, centric organisation, processes in 3 Eskom processes across Eskom

• Competency, Staff Retention • Establish an AM Framework Distribution Regions. Distribution

and Training is lacking, - prlKCSSCS andprocedures.

• Risk Management is not • Integrate AM Risk with

integrated intothebusiness Eskom process,

· Substation Maintenance

• Planning,

· Project engineering

• Project management

3.7 CO NCLUSION

Chapter two was the co nceptual phase of the research. This chapter inc luded the

literature study required for the research. The life cycle management plan was

discussed and then finally the life cycle management plan used in the utility was

co nsidered, The fo llowing chapter is the implementation stage of the research. It will

cove r the study of power transformers in terms of life cyclemanagement.

Page30

Chapter4: Case study-power transformers

CHAPTER 4 - CASE STUDY - POWER TRANSFORMERS

4.1 INTRODUCTION

Transformers are the most important yet expensive piece of equipment found in a

substation. Due to this, transformers require specialised skills and knowledge to

monitor and maintain. Power transformer's life cycle plan must be developed since it

is in the utilities best interest to make efficient use of transformers without creating

operational and maintenance problems.

4.2 THE RECOMMENDED LIFE CYCLE MANAGEMENT OF POWER

TRANSFORMERS

Power transformers are static equipment, their failure rate is very low compared to

other assets found in substations but because they are bulky, they require more time

and special arrangements should there be a failure [24]. The utility must have

measures inplace to reduce the lead-time inprocuring and replacing transformers that

could fail.

A life cycle management plan for power transformers should be inplace to ensure that

power is supplied to customers and risk to the network is minimised. Risk analysis

and condition assessment of power transformers will be discussed as well as life cycle

decisions [22] [24] [50].

Page 31

Chapters: Casestudy-power transf o rm ers

Life cycle management for power transformers or any other assets in the e lectricity

uti lity can be described by Figure 17. It exemplifies the relationship between the

technical, economical and environmental aspects to consider when making lifecycle

decisions forpowertransfonncrs or anyother asse ts.

Decision1--...

support

Figure 17:The decisi on support mechanism oflife cycleengineering [5 1].

4.2.1. W ilY TRANSFORMERS FA IL

"Basic power transformer failure models focus on the paper insulation failures and

where the withstand strength of the paper will decrease due to heat, moisture and

oxidation" [50].

Therefore in a nutshell, transformers fai l due to the following two reasons:

• Neglect over long period of time,

• Eventscausing distres s to transformers components.

Page 32

Chapters : Casestudy-power transformers

Cellulose insulation is a major component in a transformer. Cellulose has several

hundreds times the affinity for moisture that oil [31]. Therefore, once moisture is in

the transformer, most of it ends lip in the cellulose insulation. Figure 18 was taken to

illustrate the ac tivepart of a transformer which contains windings that are covered in

ce llulose.

Figure 18: Active part of a transformer,

Page 33


4.2.2. RISK ANALYSIS OF POWER TRANSFORMERS

Asset risk management is a vital part of life cycle management for utilities that are

asset centric. It involves identifying your risk exposure and being able to manage it.

We define risk as the sum of likelihood of a failure occurring multiplied by the

consequence thereof [47].

Risk assessment for a particular asset isthe process used to analyse the probability as

well as the potential impact of an identified risk. This will enable the determination

ofthe size ofthe risk and the mitigation options thereof.

Table 2 provides the risk analysis for transformers conducted during the research for

this dissertation. This information was composed at Rotek Engineering Company.

The risks associated with transformers can be addressed byscheduling maintenance,

analysing the failure mode or consequences of risk and contingency plan and

mitigation option to limit any outage caused by the failure.

Table 2: Transformer risk analysis.

Transformer Risk Analysis

Key risk from Consequence of risk Mldgatlon optionfailure

a) Exposures at failure to workers - flying a) Know condition! risk of explosivedebris.hot oil. fire. flash burning. failure.

1. Safety b) Exposure due to poor practises - falling b) Staff training perform a riskfromtank/bushings,confined spaceentry. assessment for all tasks

c) Fire resistance fluids in some casesa) Majoroil loss on burst tank a) Inspection and rectificationb) Generaloil leaks b) Granules or synthetic mats

2. Environmentalc) Fire!burning oiVPCB c) Bund wall or oil separatorsd) In-service noise d) Firprotection system

e) Firtraining staff0 Noise enclosure

a) Loss of supply - impact on the Risk management to get endorsementperformancemeasures ofa utility andcorrective action.

b) It is a legal requirement for utilities to have3. Strategic a risk management plan - Regulators will

penalise.c) Poor press - on share price if poor

performance.a) Induced outages -loss ofavailability a) Understand failures caused andb) Losof un-depreciated capital value probabilities.c) Need for unplanned capital spend for b) Asset health reviews - to identify

4. Financial replacement likelihoodd) Possible loss of earnings on contracted c) Effective failurerecovery policy.

supply

Page 34

Chapter4: Casestudy-power transformers

Failure mode describes the manner in which something fails. The effects analysis

refers to study of the consequences of those failures. The purpose of the

FMEA (failure mode effect and analysis) is to take actions to eliminate or reduce

failures, starting with the highest-priority ones. The analysis can be done either in a

qualitatively orquantitatively way [25] [52] [53] [54].

A failure mode effect analysis for transformers was conducted atRotek Engineering

Company. The results are illustrated in Table 3. A detailed FMEA can be found in

Appendix B. Performing the failure mode and effect analysis can assistwith ensuring

that theoperational reliability of thetransformers is always up todate.

Table 3: Failure Mode effect and analysis forpower transformers.

ID Main Function Failure Mode Failure FailureEquipment of Fundlon Event Cause

1 Core Wears Loss of Mechanical failure DCMagnetisationMagnetic field efficiency

Construction fault,

Mechanical over voltage,

2 Windings ConductingShort Circuit damage, fault in movement of

current transformer, hot spots,insulation material. and generation ofcoppersulphide.

Enclose oil, Mechanical damage,3 Tank protect active Leakage Tankdamage materialmethod.part.

Mechanical Movement of

4Solid Isolation Insulation of Cannot supply damage, fault in

transformer, short(cellulose) the windings insulation circuit, hot spots,insulation material. ageingcellulose,

Particles in oil, water

Isolate, cool Short circuit in Conducting in oil, too hot5 Oil active part

transformer, particles inoil, oil air/water, oiloverheated is notcooled. circulation out of

function.

Isolate Fault isolation Dirt, water penetration,6 Bushing between tank Short Circuit material, damage carelesshandling.and windings on bushing

Regulate the Cannot changeMechanical

7 TapSelector the voltage Wearvoltage level level damage,

Maintain a8 Diverter switch coherent Short circuit Contact failure Contamination ofoil

current

Page 35

Chapter4:Case study-power transformers

Operational reliability is concerned with the following [54] [55]:

a) Theidentification and classification of actual failures with a view to establish

theexistence of any particular failure patternsor trends,

b) What can bedone about any failure patterns thatmay emerge, and finally.

A model that can be used to do this is called the "bathtub curve". The bathtub in

Figure 19 describes the relative failure rate of an assetover time. This curve models

the cradle to grave instantaneous failure rates versus time [54] [55].

End ofUfeWear·OutIncreasing Failure Rate

Normal Life (UsefulUfe)Low 'Constant" Failure Rate

The Bathtub CurveHypothetical Failure Rate versus Time

Infant MortalityDecreasing Failure Rate

Time ~

Figure 19:The Bathtub Curve [56].

The first period of the curve is the section where we see a decreasing failure rate.

This occurs during the early life of a transformer. Theflat section is called the lowor

constantfailure rate, failures occur more ina random sequence during this time.

The last section is the point the curve starts to slope and it is the increasing failure

rate. Thishappens when transformers become old and begin to fail at an increasing

rate.

Page 36


4.2.3. CONDITION ASSESSMENT OFPOWER TRANSFORMERS

The failure mode and effect analysis ofpower transformers was described above, but

it does not identify the actual condition of the transformer. The second step in the

process it to perform an inspection and testing of the asset. In some instances the

residual life of the asset can be extended and the maximum return on the investment

can be achieved.

Condition assessment conducted in order to investigate asset health and to determine

maintenance timing as part of a condition based maintenance strategy. A well

planned maintenance strategy can therefore maximise a transformer's availability,

resultingincapital investment minimisation [34].

Table 4 provides the preventive maintenance plan for transformers. This table is part

of the study conducted at Rotek Engineering. Maintenance philosophies for

transformers are vital since it ensures that the equipment will remain reliable and run

for the required time of life.

Table 4: Preventivemaintenance plan for transformers.

Title 3 Months 6 Months 12 Months Scheduled Outaee

Oil Sampling X

Gasandoiloperated relay tests X

Tapchanger surge relay tests X

Axial flow fanchecks X

General fabrication maintenance X X

Valve operating checks X X

Dehydrating breather check X

Tapchanger maintenance X

Marshalling kiosk checks X

Page 37

Chapter4: Casestudy-power transformers

For transformers, very little is seen of the internals even when the tank has been

removed. Due to that, there has to be more reliance on effective diagnostics. The

diagnosis will notbe effective if the test instruments are not as accurate as they need

to be. This will require an organisation to invest in proper test instruments for their

condition assessment plans.

4.2.4. LIFE CYCLE DECISIONS

After the risk analysis is completed and the condition assessment is finished, the next

phase is the life cycle decision phase. A transformer is expensive equipment with a

low failure rate. When dealing with transformers, the following criteria have to be

evaluated [31] [53]:

a) Whether torepair, refurbish or replace aged transformers,

b) Value of redundant and sparetransformer units,

c) Overloading versus replacement,

d) Postpone maintenance or repair by installing on-line monitoring devise.

The strategies used to make decisions can suggest that all transformers be left to

service until they fail, but the cost of unexpected failure can approximately ten times

the cost of the original transformer installation. To add on to that, the time required

for rewinding or rebuilding a power transformer can take approximately six to twelve

months [57].

With that said, the following maintenance strategies can assist in preventing

transformer failure [50]:

• Time based on line tap changer overhaul,

• Time based transformer inspection,

• Time based transformer sampling,

• Condition monitoring gas-analyses.

Page 38

4.3 RIsKMETHODOLOGY

to asset

assets

assessmetnodctegy is

It involves asset cnticaltty,

asset systems rlit't",r"nn importance to

[54]

assembled in a consistent manner

assets as transformers wilt

illustrates the asset

criticality should

a

wherenv the followina equation

replacement value,

a spectnc timetrame

cost of replacmgto

are expected topopulation of

the asset same

It is

to asset

Risk (ZAR,

x

Figure 21: Model used tocalculateassetrisk [4].

This model the factors that havean impact on asset The

predictable factors that are inthe model are:

a) The current rate

b) The way in which assets are operated and maintained,

c) in the environment to which the assets are exposed,

current asset rate can modified by

as environmental factors,

inclusion

will imnrove

asset

tollowing equation [16]

p (1 (I )

p

rate.


Taking into consideration how an asset is operated and maintained will improve the

methodology of determining the probability of asset failure. The following are

aspects that an asset could endure in its operation and maintenance during its life

cycle [55] [57]:

a) Incorrect operation/maintenance due to inadequately trained staff.

b) Intentional operation above the design criteria for short periods of time due

toemergency conditions.

c) Unintentional operation above the asset's design criteria due to lack of

information.

Table 5 provides a method of assessing the risks associated with operation and

maintenance of anasset. From the assessment question in this table a score between

one andthree can be obtained.

Table 5: Assessing the risks associated with operation and maintenance ofan asset [4] [59].

Operation and Maintenance Risk Contributors ScorlOI!Catezorv No. Assessment ouestlon All Some None

1Are the relevant employees suitably qualified to

1 2 3perform the required operationsI maintenance?

2Have the relevant employees been adequately trained to

1 2 3Operational I operate the assets?maintenance stalT

3 Do the relevant employees have the necessaryt 2 3experienceandtraining experience to correctly operate I maintain the assets?

Do the employees have access to and arethey familiar4 with the relevant supporting documentation (e.g. t 2 3

operational guidelines, maintenanceprocedures etc.)

5Does the Control Centre have a record of the design t 2 3parameters of the asset?

6 Do the relevant operational I maintenance employees t 2 3Operation within

know what thedesign parametersof the asset are?

designed parametera Do all employees concerned have a common7 understanding of how operation outside the design t 2 3

parameters alTect theasset's health andasset life?

8Are records being kept of when and howlong theasset

t 2 3is operated outside itsdesigned parameters?

Table 5 contains eight questions that assist in assessing the risk contributors in the

operation and maintenance of assets. These assessmentquestions are categorised into

two groups; OpcrationallMaintenance staff experience and training as well as

operation within designed parameters.

Page 41

Chapters: Case study-power transformers

The response to the assessment questions in Table 5 will yield a numerical score that

will be used to determine the risk contribution. The minimum attainable score is 8

and the maximum score is 24. Table 6 provides an analysis of the risk contribution

from thescoring results obtained inTable 5.

Table 6: Operational and MaintenanceRisk Contribution [4][55].

Scoring O&M% Contribution to Current Asset Failure RateResult Rating

8-12 1 Negligible 0%

13-16 2 Low 5%

17-20 3 Average 10%

21-24 4 High 20%

4.3.1. ENVIRONMENTAL FACTORS

The environment in which an asset is operated and maintained must be taken into

consideration. The impact from external factors within the operating environment

plays a role in determining the probability of asset failure. These extemalfactors

within an operating environment can be natural events, theft or vandalism. Table 7

provides a list of environmental factors that considered being significant contributors

to asset failure.

Table 7: Environmental factors included in the Risk Model [4] [55] [59].

OperatingNo Environment Assessment criteria

Factor

1 Lightning Probability that lightning will cause failure, based onthe asset type and thelizhtninz densitv for the immediate lleOllfaDhical area.

2 Wind Probability thatwind will cause failure, based ontheasset type, and maximumwind speed.

3 Snow and hail Probability that snow and hail will cause failure, based on the asset type andfreauencv of snow and hail storms.

4 Flooding ProbabiIi ty that flooding will cause failure, based on the asset type andfrequency of flooding occurrence.Probability that pollution (inclusive of corrosive pollution and other polluting

5 Pollution deposits causing flash-over and other events) will cause failure, based on theasset tvne and R!ude ofDollution in theimmediate vicinity.

6 Vandalism I theft Likelihood of vandalism I theft causing failure, based on the asset type, andfrequency of vandalism I theftoccurrins in the vicinity ofthe asset.

Page 42


4.4 CONCLUSION

This chapter was the theoretical implementation phase of the research. It focused on

the life cycle management for power transformers. The different stages of the

transformer life cycle were analysed and discussed.

The next chapter is the conclusion of this dissertation. This chapter will provide the

shortcomings of this dissertation, recommendations and proposed further work to be

conducted.

Page 43

Chapters: Conclusion

CHAPTER 5 - CONCLUSION

5.1 INTRODUCTION

The fifth and final chapter of this dissertation will provide asummary and conclusion.

From the study and case study of this dissertation recommendations will be made and

a discussion ofshortcomings is provided.

5.2 GENERAL CONCLUSION

A life cycle approach enables product designers, service providers, government agents

and individuals to make choices for the longer term and with consideration of all

environmental media. Life cycle approaches avoid shifting problems from one life

cycle stage to another. It is therefore an ideal way ofmanaging an electric utility such

as Eskom.

The study was a success and can be investigated in depth with a more detailed

assessment on the technical side. There was however no success with the

development of a complete asset management plan which complies with PAS 55

(Publicly Available Specification) published by the British Standards Institution for

asset management.

This was partly due to the electricity utility's need to be audited and accredited with

PAS 55 which is in progress. There iscurrently a two year pilot project at Eskom to

incorporated asset management in their business. This project will assist in

completing this study.

Page 44

Chapter5: Conclusion

5.3 PROPOSED FURTHER WORK

The aim of this dissertation was to investigate methods that electricity utilities use in

order to implement asset life cycle management. There are a number of shortcomings

that were identified in this dissertation. Some of the areas proposed for further work

includethefollowing:

a. Investigating the impact of the human factor in asset management.

The human factor was not discussed inthis research but should be part of any further

work. People have an impact on themaintenance systems and the management of any

organisational strategies.

b. Investigate how life cycle costing affects asset management from the

acquisition phase to the utilisation phase.

Improving reliability of equipment is a topic that was discussed but not in detail.

There are several tools used by utilities to assist with life cycle costing. The

investigation into the methods and procedures used in a project, product and system

life cycle can be included in further work.

c. Investigating and improving the maintenance loop.

The utility's current structure does not support asset management since there is no

formal risk management structure, poor integration between planning and

refurbishment. There are limited specialists and resources as well as poor

maintenance skills withinthe utility.

It is recommended that the utility must manage its risk across the asset life cycle

stages. This should be conducted in compliance with PAS 55 in order for the utility

to be fully asset centric. This includes the establishment of a department within the

utility thatmanages assets in the business.

Page 45

Chapter5: Conclusion

This department should be made upof the following sections:

• Life cycle cost management of the assetsused,

• Risk management for assets and the network,

• Training and development,

• Project planning and management

• Maintenance management, and

• Communication.

Typically found inother life cycle managements plans, is that the end user does not

correctlyutilise the strategic measures and standards in place. It is recommended that

training, awareness and the importance of systematicalIy executing the plan will

ensure thatthe life cyclemanagementplans will be effective.

In the conclusion of the dissertation: It is recommended that Eskom Distribution

considers the implementation of recommendations mentioned in this dissertation.

This will result inamajor cost saving for the organisation.

Page 46

111111

ApPENDICES

APPENDIX B: POWER TRANSFORMER FMEA

Power Transformer FMEA 1311 ISO) (54) ISS)

1. COMPONENT DESCRIPTION: CORE

Function of Component Functional Failure Failure Mode Failure Effect Root Cause Monitoring

A. Fail to efficientlyI.Efficient Magnetic link I.Vibration monilOring,2.FRA

magnetically link the 1.Core Bracing failure I.Delamination Poor workmanshipbetween the Windings

windings(future Technology)

2.Clamping arrangementShort Circuit

loose

3.Clamping over stressed Design failure

4.Broken Welding

5.Transfonner Noise Ditto

1.lnsu1ation failure

between the core

2.Core down to earth 1.Ditto clamp. bolts and I.DGA

p1ates(Chemical and

dielectric)

2.LocaIised heating

3.Gassing

Excessive eddy

3.Lamination Insulation failure 1.Ditto current resulting in 1.DGA

overheating

2.Localised heating

3.Gassing

4.Corrosion I.Dilto oil sample

2.LocaIised heating

Page48

ApPENDICES

2. COMPONENT DESCRIPTION: WINDING


I.Efficiently Transfonn A. Fail to transform voltage!I.Collapsed windings I. Short circui L I.Extema1 short circuit DGA

voltage! conduct current conduct current

2.Bracing Failure

3. Intertum fault

2.GassingI.Manufacturer or design

or repair defect (dry-out)

2.1ntertum winding faultI. TOY (no Arresters or

All oil testsI.Short circuitincorrect placement).

2. Insulation failure due to

moisture


short circuit


quality ofoil

2. Deformation of winding. I.Ditto

3.Winding harness I.Short circuit I.Loose connections Impulse test

2.Clearances (leads and

Tank/Core frame)

3.Clearances (leads

between themselves)

4.Clearances(Leads

among phases)

Page49

ApPENDICES

l.POOR

2.Open circuitlbreak in continuity CONNEcrIONS(CRIMP DGA

lNG/SOLDERING

4. Paper degradation I.Mechanical I.Short circuit FuranicIDPIDGA

2.Heat

2.Chemical I.Moisture Oil Tests

2.Acidity

3.0xygen

3. COMPONENT DESCRImON: MAIN TANK(lndudes Gaskets Rings, valves, FlasbSbields)

Function of Component Functional Failure Fallure Mode Failure Effect Root Cause Monitoring

l.Protect inside contentsA. Moisture in oil I.Leaks I.Environmental l.Skill

against Undesirable elements

2.Workmanship

3.Non-standard parts

2.Corrosion

3.MechanicalI.Manhandle,transportatio

impact recorders, job observationsn.rigging skill

4.Gasket failure I.SkillNew units must be re-torqued again

after 3 months

2.Workmanship

3.Non-standard parts

2.Structura1ly SUpport Inside A. Failure to structurally Impact recorders, Monitoring,I.Mechanical (bolts breaking) I.Location boltsIBrackets broken I.Manhandling(rigging)

parts support inside parts inspection

2.Earth tremors

Page 50

ApPENDICES

3.Short circuits

3.Structurally support A. Failure to stJUeturally I.WateraceumulationI.Corrosion l.Brackets/bolts Visual inspections

Outside pans support outside pans through poor design

2.Sub-standard corrosion

protection

2.Pipework l.Poor clamping

2.Mechanical I.Location bolts/Brackets broken 1.M.anhandling(rigging)

2.Eanh tremors

3.SbOrt circuits

2.Lifting lugs/jacking points 1.Manhandling(rigging)

A. Fail 10 confine Oil inside4.Confme oil inside the tank l.Oil leak I.Massive Tank Rupture 1.Pressure PRV

the Tank

2.Slowleak I.Conosion Visual inspection

2.Gaskets failure Visual inspection

3.Weld crack Visual inspection

Page 51

ApPENDICES

4. COMPONENT DESCRIPTION: OIL(UQUID INSULATION)


1.1 Ingress ofA. Fail to insulate (Dielectric l.Water contamination - Internal flash-

I.lnsulation I.lntemal fault(Flash over) water/moisture(No Oil sampling!Failure) over(PPM)

effective sealing)

2.Free particles l.Intemal fault(Flash over) Workmanship Oil sampling!

2. Provide Effective Cooling A. Fail to provide effectiveI.Sludge I.Poor circulation Blocking ofoil ducts Oil analysislVisuall

to the Transformer Cooling

3.Protc:c:t insulation material A. Fail to protect I.insulation breakdown I.Deterioration ofoil quality Dielectric strength oil samples

DP test, funaric test

50COMPONENT DESCRIPTION: PAPER(SOUD INSULATION)


I.Degradation due tol.Insulation material A. Fail to insulate I.Chemical I.Flashover Oil tests, Tan Delta tests

moisture, heat, oxygen

2.Electrical I.Flashover I.TOV's Surge arrestors

3.Mc:c:hanical I.Flashover I.Short circuit FRA

2.Distortion I.Manhandling Impact recorders.

6. COMPONENT DESCRIPTION: CONSEVATOR TANK(iDc:lude piping)

Function of Component Functional Failure Failure Mode(Why) Failure Effect(What) Root Cause Monitoring

A. Fail to act as an OilWorkmanship(rags,closed

l. Oil Reservoir l.Blockage in the pipe l.Oil flow restriction valve,Seal paper left on inspectionsreservoir

silica gel cartridge,)

Moisture.Corrosion2.Corrosion 1.00lieak visual inspections

protection

Broken oil level indicator visual inspections

Page52

ApPENDICES

2.Transport Oil(pipe) A. Fail to transport Oil l.Welding cracks l.Oilleak. Manhandling visual inspections

Moisture, Corrosion2.Corrosion l.Oilleak visual inspections

protection

3.Breathing(pipe) A. Fail to breath l.Welding cracks l.Oilleak Manhandling visual inspections

Moisture, Corrosion2.Corrosion I.Oilleak visual inspections

protection

Moisture, Corrosion4.Support buchboltz(pipe) A. Fail to support buchholz I.Corrosion l.Oilleak. visual inspections

protection

Page 53

ApPENDICES

7. COMPONENT DESCRIPTION: RADIATOR


I. Provide Effective CoolingA. Restricted oil flow l.Blocked radiators l.Heating

to the Transfonner(oil flow)Sludge oil samples

butterfly valve closed Visual inspection, Infrared scanning

Damaged fins Visual inspection,

2. Provide Effective CoolingA. Restricted air flow I.External blockage I.Heating

Foreign(nests,vegetation,eVisual inspection,

to the Transformer(air flow) te) blockage

3. Provide Effective Cooling

to the A. Reduced emissivity( I.Cover with low emissivity coating l.Heating Pollution Visual inspection,

Transformer(Emission)

8. COMPONENT DESCRIPTION: BUSWNGS Oncludes conductor Connections)


l.Provide path from externalLightning,(to be moved to

conductor to internal A. Fail to insulate 1. External flash-over

conductor (insulate)windings)

Pollution Visual inspection

ForeignVisual inspection

objects(birds,monkeys)

2. Capacitance insulation fail - causing I.Explosion of bushing + oil spillMoisture, partial discharge Tan delta test

electrical fault (possilble fire)

Test-pin connectionllead

damagedTan delta test(capacitance value low)

3.Moisture ingress I.Explosion of bushing + oil spill Seal tap insulation test

Page 54

ApPENDICES

(possilble fire)

Sub-standard material Quality checks on Manufacturers

Poor workmanship Quality checks on Suppliers

4. Porcelain damage-Explosion of bushing + oil spill

VandalismlFlash over Visual inpection(possilble fire)

Damage by adjacentVisual inspection

equipment failure

Flash-over Vandalism Visual inspection

Damage by adjacentVisual inspection

equipment failure

2.Provide path from external Poor

conductor to internal A. Fail to conduct I. Loose connection- hot connection worlonanship(Crimp.Swea Infra red

conductor (conduct) t.Bolt)

Visual inspection

A. Fail to contain oil (fallI. Grouting degradation-crack Oil spill evident Poor material Quality checks on suppliers3.Contain Oil

under FCI)

Canti lever loading Visual

2. O-ring I gasket/Grommet failure Oil spill evident Poor material

Canti lever loading

3. Gauge glass leak. Oil spill evident Poor workmanship Observations

4.Porcelain crack Oil spill evident Poor worlananship Observations

Poor design(Conductors5.Cantilever loading Oil leak Quality checks on design

supported by bushings)

Vandalism Visual

Canti lever loading Visual

9. COMPONENT DESCRIPTION: BUCHHOLTZ

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ApPENDICES


I.vibration 2.materiaIl.Provide Alann pulse A. Fail to provide alann 1. Switch fail (Mercury or Reed) I.No immediate noticeable effect visual inspection during maintenance

fatigue

2. failure of internal mechanism or LNo immediate noticeable effect Lvibration 2.materiaI

float 2.sustained alarm fatiguevisual inspection during maintenance

pet cock assembly/pipe3.fail to contain gas gases escaping

leakingvisual inspection during maintenance

1.vibration 2.material2.Provide Trip pulse A. Fail to provide trip I. Switch fail (Mercury or Reed) l.No immediate noticeable effect visual inspection during maintenance

fatigue

2. failure of internal mechanism or I.No immediate noticeable effect 1.vibration 2.material

float 2.sustained trip or no tripping fatiguevisual inspection during maintenance

manhandling(installation)

2.material3.Contain Oil A. Fail to contain oil L Inspection glass/plastic crack 2. LOil spill visible 10 operator visual inspection during maintenance

incompatibility(perspex

used )

Manhandling (installation)

2.gasket damage/perished I.Oil spill visible to operator 2.age 3. Material visual inspection during maintenance

incompatibility

3.Leak at sampling valve I test valve I.Oil spill visible to operatorManhandling (installation)

visual inspection during maintenance2.age (o-ringlseal) 3.

Page 56

APPENDICES

10. COMPONENT DESCRIPTION: COOUNG SYSTEMS (FANS)


A. Fail to cool the l.transfonner temperature mechanical/electricalI.Cool the Transformer I.motor not working visual inspections

transformer increasing(otilwti) (many)

I.transfonner temperature2.broken fan blades mechanical (many) visual inspections

increasing(otilvni)

l.transformer temperature3.fan assembly broken/detached mechanicaVeovironmental visual inspections

increasing(oti/wti)

11. COMPONENT DESCRlmON: UREATHING MECHANISM


LOry the breathing aiI{silica l.Discolouration, noticeable toA. Fail to dry breathing air 1. Silica gel spent (no longer active) service intervals Visual inspections

gel) operator

incorrectly sized

breather(to small)Visual inspections

gaskets/sealing washers

damagedVisual inspections

container damaged Visual inspections

flanged/threaded

attachment damaged Visual inspections

/leaking

breather pipe rusted Visual inspections

conservatorl.Brown discolouration, noticeable

2. Silica gel contaminated with oil overflow(caused by trf Visual inspectionsto theoperator

internal fault/overfilling)

Visual inspections

Page 57

ApPENDICES

Visual inspections

3.Threaded/flanged arrangement fail to dry air/discoloration from theincorrect installation Visual inspections

damaged top

2. Assist with breathing A. no breathing I.silica gel pennanendy blue fail to breath silica gel car1ridgesealed Visual inspections

flanged gasket with noVisual inspections

hole

2. Breather (container) not sealing at I.Discolouration from top of

the top flange because gasket failed containermanhandling Visual inspections

materialIdesignVisual inspections

substandard

flanged/threaded

attachment Visual inspections

damagcdlleaking

breather pipe rusted Visual inspections

3. Remove particles fromA. Fail 10remove particles

l.No / low oil level, visible tooil bowl cracked/broken

air(oil bath)I. Bottom oil bath empty

operator/oil leakVisual inspections

trf surge(clear the bowl ofVisual inspections

oil)

poor workmanship Visual inspections

incorrect

installation/vertical

12. COMPONENT DESCRlmON: TAP CHANGER

Fuacdoa ofCompoacat Fuacdoaal Failure Failure Mode Failure Effect Root Call5e Moaitoriag

l.Profdes gearing (gearingA. fail to provide gearing Visual Inspection (Done ofT

ratios between motor and I.Geneva sheared pin In-correct/no selection Mechanical fatigueand selection loadyrests

tap change

Page 58

ApPENDICES

(Selcetor!Di\'Crter) s",itehcs

(Tap change mechanism)

Visual lnspcction (Done ofT2.Sheared shaft In-correct/no selection Mechanical fatigue

load)ffests

Visual Inspection (Done ofT3.Damaged gears In-correct/no selection Mechanical fatigue

loadyreslS

2.Selccts appropriateA. Fail to select appropriate

tJp

position off·load during tJptap position off·load during I.Uncotrolled tap positioning(Oul of

In-com:ctloo selection Tap ",inding damage Tap changer test (Speed lest!UV leSt)

changing(SelcctOl' switch)tap cbanging(Selcctor alignment)

S""ilch)

3.Divuts c:urn:Dt on load

during lap changing(Di\-ater A.. Fail to divert I.Tap change failure Burning of Resistor

switch)

2.Sequence 001 of line

l..mechanical failure

during sdCClOr/divcner

".Limit" the flow_ilching(l.e.slow

aun:nIl.winding damage 2.cxcessivc switehing.brok.en

during tramitioo(TransitiOll A.. fail to limit I.resistor damagc(pan1y shorted out) Conditioo monitoringcontact wear pins/geneva wheels/fly

resistor)",mel and spring andIOI'

charging assembly broken

)

1.mccbanica1 failurel.winding damage 2.excessi\"c

2.resislOr open circuit(more common) during sdcetor/divcner Conditioo monitoringcontact wear

swilching(Le. slow

Page59

ApPENDICES

switching, broken

pins/geneva wheels/fly

wheel and spring and/or

charging assembly broken

)

5.Detect any over pressure ( A. Fail to detect overCable gland seal not

Tap change pressure pressure in the diverter I.Diaphragm damage No trip/in correct tripproper/Cover seal

relay(Component» compartment

Cable gland seal not2.Spring damaged No trip/in correct trip

proper/Cover seal

Cable gland seal not3.Corrosion No trip/in correct trip Visual inspection/Calibration Test

proper/Cover seal

6.Deteet any surge ( TapA. Fail to detect surges in the Cable gland seal not

change surge I.Corrosion No trip/in correct trip Visual inspection/Calibration Test

relay(Component»diverter compartment proper/Cover seal

2.In correct calibration No trip/in correct trip In correct Installation Calibration

7.Conduct current( Moving excessive mechanical and/or1. Misalignment 2.contact

Condition monitoringlVisualloiIA. fail to conduct l.no contact! insufficient contact assembly damaged

contacts) electrical wear sampling3.substandard materials. 4.

excessive mechanical and/or2.Material fatigue

electrical wear

1. Misalignment 2.contact

Arcing assembly damaged

3.substandard materials. 4.

heat /current flow due to3.Coking ofcontact carbonising ofcontact Visual

lack of tap movement

Page 60

ApPENDICES

8.Conduet current( Fixed excessive mechanical and/orI. Misalignment 2.contact

Condition monitoringlVisua1loilA. fail to conduct I.no contact! insufficient contact assembly damaged

contacts) electrical wear sampling3.substandard materials. 4.

excessive mec:hanic:al and/or2.Material fatigue

electrical wear

I. Misalignment 2.contact

Arcing assembly damaged

3.substandard materials. 4.

heat fcurrent flow due to3.Coking ofcontact carbonising ofcontact Visual

lackoftap movement

9.Keep tap changer oilA. Fail to keep oil separate I.mechanical fatigue,

separate from main tank l.craking leaking oil samplebetween electrical failure.3.sealing

oil(Barrier board)

1.overtension,2.Substanda2.bobbin failure leaking visuals, training

rd material

13. COMPONENT DESCRIPTION: l\Iecbanleal boxIMotor drive

Function orComponcnt Functional Failure Failure Mode FaUure Effect RootCausc Monitoring

I.Stores energy A. Fail to store energy Broken Springs I.No charging of flywheel

2.Bumt motor, Broken fan belt

3.lnterlock switch for manualLack ofskiU visual

o~tingnotwor1<ing

2.Wipe contact A. Wiping contact failure corroded wiping contacts I.Heater not working

2.Wiping not done after transformervisual,condition monitoring

is stationery for a long period

3.Heater A. Fail to keepmoisture out I.Not connected Corrosion frust visualinspection

2.Nopower

3.Broken wires

Page 61

ApPENDICES

4.Seals A. Fail to keepmoisture out l.Rust No inspection done Neglect visual inspection

2.Moisture

S.Limit switches(wipingA. Fail to keepwithin limits Fail to store energy Cause manual reset Condition monitoring

contacts)

6.Linkage betweenA. Fail to link Mechanical

Mechanical box and Selector 1. Broken Shaft No tap changing visual inspectionBox and Selector

(MRBox)

2.No settings done when changingTraining of Staff visual inspection

Mechanical boxes

14. COMPONENT DESCRIPTION: PRVIEXPLOSION VENT(BELCH PIPE)


I Act as a pressure relief for incorrect installationA. fail to relieve oil pressure I.incorrectly sized prv damage to transformer Visual

the main tank lmaintenance

2.incorrectly sized/type diaphragm in incorrect installationdamage to transformer Visual

explosion vent lmaintenance

2.Pressure release at A. pressure released too incorrect installationt.spring not applying correct pressure oil leak Visual

appropriate time quickly lmaintenance

incorrect installation2.sealing arrangement damaged oil leak Visual

lmaintenance

A. internal faults/external

3.incorrectly sized prv oil leak faults, oil head, incorrect Visual

installation lmaintenance

A. internal faults/external4.incorrectiy sized/type diaphragm in

oil leak faults, oil head, incorrect Visualexplosion vent

installation lmaintenance

S.incorrect filling ofoil oil leak poor work practice Visual

6.incorrect transportation oil leak poor work practice Visual

Page 62

ApPENDICES

I I I I I15. COMPONENT DESCRIPTION: TEMPERATURE GAUGES(OIL AND WINDING)

Function ofComponent Functional Failure Failure Mode Failure Effect Root Cause Monitoring

1.wor1<manship(Training),

Fail I. No/lncorrect readings2.Corrosion (Gauge seal,

to measure temp.Measure temperature(Oil) I.BrokenlMissing capillary tube Cable Visual, Testing/Calibration

laccurate temp. 2.Nuissance alannsltrippingglancing),3.Capil1aIy tube

sealing)

l.workmanship(Training),

2.Capillary pockets full of 1. NolIncorrect readings2.Corrosion (Gauge seal,

Cable Visual, Testing/Calibrationwater/solvent 2.Nuissance alannsltripping

glancing),3.Capil1aIy tube

sealing)

I.workmanship{Training),

1. NolIncorrect readings2.Corrosion (Gauge seal,

3.Capillary pocket Empty ofoil Cable Visual, Testing/Calibration2.Nuissance alannsltripping


sealing)

I.workmanship(Training),

4.Instrumentlmechanism I. NoIIncorrect readings2.Corrosion (Gauge seal,

Cable Visual, Testing/Calibrationdamaged/corroded 2.Nuissance alannsltripping


sealing)

l.workmanship(Training),

Measure Fail to measure temp. 1. NoIIncorrect readings 2.Corrosion (Gauge seal,

tcmperature(Winding) /accurate temp.I.BrokenlMissing capillary tube

2.Nuissance alannsItripping CableVisual, Testing/Calibration


Page 63

ApPENDICES

sealing)

2.Capillary pockets full of I. NoIIncorrect readingsditto Visual. Testing/Calibration

water/solvent 2.Nuissance alarmsItripping

I. NoIIncorrect readings3.Capil\ary pocket Empty ofoil ditto Visual. Testing/Calibration

2.Nuissance alarmsItripping

4.lnstturnenl/mechanism I. NoIIncorrect readingsdiuo Visual, Testing/Calibration

damaged/corroded 2.Nuissance alarms/tripping

I S.CT/resistor damageI. No/lncorrect readings 2.No or

CorrossioaResistor), Testing.incorrect alarms/tripping

16. COMPONENT DESCRIPTION: SURGE ARRESTORS

FallCdoa 01 COlllpOllftil F..cdo.... Fallarc Failure Mode Fallarc Erred a-Caase MoaitoriD&

I.incorrect applieatiool.Protectioo of main I.equipment failure(noticeable) and totaL'partial destruction, no

A. Fail to protect 2.TOV \isua1, Testing(SpecW equipment)equipment (TrmsfonDCf) unnoticeable noticeable effect

3.Pollution.4.Vanda1ism

S.DOa applkatioa or

GradiD& riDe ..-baa

rrqllired

17. CU\IPONENT DESCRlmOl'lf: OILLEVEL INDICATOR

Faactioa or COlllpOllC1l1 FuctioaaJ Fallan Failun Mode Fallun Effed RoolCatie MoalloriD&

Page 64

ApPENDICES

Polluted gauge, workman

ship, sub standardI.Measure oil level A. fail to measure I.broken gauge,(Linear type) Trftrip on low oil visual

material. contaminants in

oil(linear oil gauge)

Wrong indication

Broken gauge glass can cause oil

leak

2.broken gauge,(dial type) Trf trip on low oilCracking/filling

visualuplbreaking of float

Broken gauge glass can cause oilBending of floatarm visual

leak

Wrong indicationfloat gearing mechanism

visualbroken

Dial indicator glassvisual

broken

Corrosion(Gauge covervisual

seal)

oil leak due to shaft seal visual

Page65

ApPENDICES

18. COMPONENT DESCRIPTION: EARTIUNG

FUDetioDof COmpoDCDt FUDctiooaJ Failure Failure Modc Failure Effcct Reet Caase MOnitOriDg

I.Provide effective step and touch potential will beA. fail to provide Loose connection workman ship Visual! Test (earth cont.)

eanhling(Protection) affected

No continuity to earth mat

Theftstep and touch potential will be

theft Visualffest (earth cont.)affected

No continuity to earth mat

Non standard earthing used bum offduring fault currents workmanship Visual

Copper and galvanized steel(1int

marts)

19.COMPONENT DESCRlmON: OIL PUMPS

FUDctioDor COmpoDtDt FunctioDai Failure Failure Modt Failure Efftct RootCaase Monitoring

faulty pump,2.faulty

I.circulate oil A.fail to circulate oildifference in oil temperature within a

over heat leading to tripwindingfoil temp.

tank gauge.3.No supply to oilVisual, Electrical test

pwnp.4.Pump motor fault

10. COMPONENT DESCRIPTION: MIB's(SpUt betweeD F'S and EDF'S)

Fuactioa or Compoacut FaoctioDal Failure Failure Mode Failure Effect RootCaase Monitoring

Page 66

ApPENDICES

l.Contain

proccc:tioG'mctcring ICT A.fail to contain I.Loose cable glands open circuit OIl ITs Wor\:manship Visual

cable COIlIlCCtions

2.Conncctioas nol tighlc:Dcd Rain waler ingress into boxesNo effective sealing at

doors

3.COITOSion Ingress of insects(Dirt)

unnecessary Trips due to4.Moistures,

water(Rain)

5.Blockcd air vents,

6.Thcft

Page 67

REFERENCES

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