polymer insulators
TRANSCRIPT
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 1/104
KING SAUD UNIVERSITYDEANSHIP OF SCIENTIFIC RESEARCH
Research Center – College of Engineering
Final Research Report No. EE-18/26/27
EFFECT OF THERMO-ELECTRICAL
STRESSES AND ULTRA-VIOLET
RADIATION ON POLYMERIC
INSULATORS
By
Dr. Y.Z. Khan, Prof. A.A. Al-Arainy,
Prof. N.H. Malik, andDr. M.I. Qureshi
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 2/104
Table of Contents
Page
List of Tables iii
List of Figures ivAcknowledgement vii
Abstract (Arabic) viiiAbstract (English) ix
Nomenclature x
CHAPTER 1: INTRODUCTION 1
1.1 Polymer Insulators: Advantages and Disadvantages 3
1.1.1 Advantages 3
1.1.2 Disadvantages 5
1.2 Types of Insulating Materials 5
CHAPTER 2: LITERATURE REVIEW AND DATA COLLECTION 8
2.1 Introduction 8
2.2 Basic Polymeric Insulators Components 9
2.2.1 Core 92.2.2 Weather Sheds 10
2.2.3 Housings 132.2.4 End Fittings 14
2.3 Insulator Types 142.4 Weathersheds of Polymeric Materials 17
2.5 Testing Methods of Composite Insulators 21
2.6 Test Results of Composite Insulators 222.7 Ranking of Materials for Outdoor Insulation 26
2.8 Effect of Voltage Polarity on Performance 28
2.9 Properties of Pollution on Polymeric Insulators 302.10 Artificial Contamination on Polymeric Insulators 32
2.11 Aging of Polymeric Insulators and Mechanisms of Failure 33
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 3/104
Page
CHAPTER 3: EXPERIMENTAL SETUP AND PROCEDURES 45
3.1 Significance of Accelerated Aging of Polymeric Insulators 45
3.2 Accelerated Aging Cycle 473.3 Design of Accelerated Aging Test Chamber 48
CHAPTER 4: RESULTS AND DISCUSSIONS 58
4.1 Lightning Impulse Withstand Tests 58
4.2 Dry and Wet Power-Frequency Withstand Tests 60
4.3 Scanning Electron Microscopy (SEM) of Samples 624.4 Hydrophobicity 64
4.5 X-Ray Photoelectron Spectroscopic (XPS) Analysis 65
CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS 72
5.1 Conclusions 72
5.2 Recommendation for Future Work 73
REFERENCES 74
ANNEX – I 88
ANNEX – II 90
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 4/104
List of Tables
Table No. Title Page
2.1 Polymer Insulator Data for Saudi Electricity
Company (SEC-EOA). 42
3.1 Details of insulators under test. 53
4.1 Concentration (%) of elements detected byXPS. 69
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 5/104
List of Figures
Fig. No. Title Page
1.1 Composite insulators used in the world [1]. 2
1.2 Classification of insulating materials. 6
2.1 Components of polymer insulator. 9
2.2 Surface resistance of bare and silicone-coated porcelain insulators under salt fog conditions
[3]. 12
2.3 Dead End / Suspension type polymeric
insulators (~15 kV). 14
2.4 Line post type polymeric insulators (~15 kV). 15
2.5 Photographs of the lines with suspension type
insulators. 16
2.6 Line post insulators. 16
2.7 Guy strain type polymeric insulators. 17
2.8 Dependence of the withstand voltage on
(equivalent salt deposit density) ESDD in SIRand porcelain insulators [3]. 24
2.9 Cumulative charge in EPDM and HTV-SIRrods during exposure to energized salt-fogshowing the differences between ac (60 Hz),
+dc and –dc. Conditions: conductivity of thesaline water forming the fog is 250 µS/cm;
electrical stress is 0 6 kV/cm [29] 29
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 6/104
List of Figures
Fig. No. Title Page
2.11 Electric field along an insulator as a function
of shed number showing the effect of threesimulated defects placed in a groove in EPDM
insulator. Lengths of defects, 16 to 32 cm[65]. 38
3.1 Accelerated aging cycle. 48
3.2a Schematic diagram. 49
3.2b Photograph of test chamber for accelerated
aging cycle. 49
3.3 Spectrum comparison of sunlight & UVradiation [76]. 51
3.4a Schematic diagram of 28 kVL-L polymeric
insulator. 52
3.4b Dead End/ Suspension polymeric
insulator(EPDM and TPE). 52
3.5a Photograph of transformer used. 53
3.5b Transformer connections used in testing. 54
3.6 Temperature variation on insulator surface(under no load) and UV-A radiation level inthe Central region of Kingdom (Riyadh). 55
3.7 Temperature rise and fall variation in
Chamber 56
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 7/104
List of Figures
Fig. No. Title Page
4.2 Schematic of tests under lightning impulse
voltage. 59
4.3 Comparison of flashover voltages underlightning impulses of both polarities. 60
4.4 AC setup for testing of one unit of suspensioninsulator. 61
4.5 Flashover voltage under 60-Hz AC voltage. 62
4.6 SEM micrographs for new and the aged
samples of SiR and TPE insulators. 64
4.7 XPS analysis of SiR. 67
4.8 XPS analysis of TPE. 68
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 8/104
ACKNOWLEDGEMENT
The authors would like to thankfully acknowledge the assistance and
financial support provided by the Research Center, College of Engineering,
through research project grant No. 18/426. Sincere thanks are extended to the
staff of High Voltage Laboratory, Electrical Engineering Department where
most of the experimental work was carried out.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 9/104
لمل ص
وه ي تن تج ت ستخدم الب ولمرات عل ى نط اق واس ع ف ي آثي ر م ن التطبيق ات الكهربائي ة
تستخدم العوازل البولميرية بصورة متزاي دة ف ي خط وط.وتستخدم في المملكة العربية السعودية
ة آبي رة الخ صائص الكهربائي ة لتل ك الع وازل بالعوام لتت أثر ب ص.النق ل والتوزي ع الكهربائي ة
تلك الع وازل البولمبري ة الم ستخدمة ف ي خط وط الق وى.البيئة هذه الدراسة تهدف إلى تقويم أدا
رس ت أثير األش عة ف وق.الكهربائي ة تح ت الظ روف البيئ ة للمنطق ة الوس طي م ن المملك ة
د
أدا
ى
عل
رارة
الح
ة
درج
اع
وارتف
سجية
وازلالبنف
الع
ك
تل
.ق
وطب
مم
ص
دف
اله
ذا
ه
ق
ولتحقي
الظروف المناخية المحلية وذلك باس تخدام نظ ام المواص فات الدولي ةلمحاآ)تعتي(نظام تعمير )IEC 61109(ا هيلع تاليد عتلا ض عب لا خدإ ع م.ة يئابرهكلا صئاص خلا ت نروق د قو
.عميروالبصرية والمظهرية والكيمياية لتلك العوازل قبل وبعد الت
أدا م ن الب ولمر))TPEأظهرت اختب ارات الع زل أن الب ولمر المط اطي الم رن أف ضل
بSiR ( (حي ث بين ت النت ائج إنخف اض ج ودة الع زل يع د التعمي ر ل ) )SiRالمط اطي ال سليكوني
10%و
صاعقي
ال
الجهد
حالة
في
7%ة
حال
ي
ف
ذآر
ي
ر
التغي
ن
يك
م
ول
ردد
المت
د
الجه
ة
حال
ي
ف )TPE. ( بولزاو علا حط سأ ةنوش خ دا يدزا ةيرص بلا تارا بتخالا جئا تن تر هظأ ة لثامم ةف
تغيي ر ي ذآر عل ى أس طح الع وازل الم صنوعة م ن ) )SiRالمصنوعة من مع التعمير ول م يط را
)TPE. (لزاوع حطسأ ةنوشخ دايدزا)SiR (ي ف صقا نت ببس ي دق ةئيبلا لماوعلل ضرعتلا دعب
.جودة العزل لتلك العوازل
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 10/104
ABSTRACT
Polymers are widely used for a variety of electrical applications and are
being produced and used in the Kingdom of Saudi Arabia. Polymeric
insulators are finding increasing applications in overhead transmission and
distribution lines. The electrical properties of such polymers are strongly
influenced by environmentally induced degradation mechanisms. A survey
was carried out by the authors to determine the state of non-ceramic insulators
being used by the power utilities in the Kingdom. To check the suitability of
the polymeric insulators, an experimental investigation was also carried out.
This experimental investigation is aimed at assessing the performance of
polymeric insulators used in high voltage overhead transmission and
distribution networks in the environmental conditions of central Saudi Arabia.
The effects of ultraviolet radiation and heat on the polymeric insulators were
studied. To achieve this objective, an accelerated aging test chamber was
designed and implemented to simulate local atmospheric conditions based on
the modified IEC standard 61109. Electrical withstand and Scanning Electron
Microscopy (SEM) based optical, visual and X-Ray Photoelectron
Spectroscopy (XPS) based chemical analytical results of the laboratory aged
insulators were compared with the new ones.
Dielectric performance shows that Thermoplastic Elastomer (TPE)
insulators outperform SiR insulators, since the reduction under aging exceeds
10% under lightning impulse while it amounts to around 7% under power
frequency test voltage while TPE insulator exhibit just minor reduction.
Similarly, the optical results indicate that surface roughness of the aged
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 11/104
NOMENCLATURE
SEM Scanning Electron Microscopy
XPS Photoelectron Spectroscopy
TPE Thermoplastic Elastomer
SiR Silicon Rubber
UV Ultraviolet
PTFE Poly Tetra Floro EthylenePE Polyethylene
EPDM Ethylene Propylene Diane Monomer
EPR Ethylene Propylene Rubber
RTV Room Temperature Vulcanized
HTV High Temperature Vulcanized
EPM Ethylene Propylene MonomerIEC International Electrotechnical Commission
EVA Ethylene Vinyl Acetate
HDPE High-Density Polyethylene
PUR Polyurethene
ATH Alumina Trihydrate
ANSI American National Standards Institute
NEMA National Electric Manufacturers Association
ESDD Equivalent Salt Deposit Density
NSDD Non-Soluble Deposit Density
ESCA Electron Spectroscopy for Chemical Analysis
FTIR Fourier Transform Infrared
LMW Low Molecular Weight
GC Gas ChromatographyMS Mass Spectrometer
TGA Thermogravimetric Analysis
RIV Radio Influence Voltage
SEC Saudi Electric Company
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 12/104
1
CHAPTER 1
INTRODUCTION
Overhead line insulators are used to support the line conductors at
towers or poles and to separate them electrically from each other.
Traditionally, line insulators have been produced using high quality glazed
porcelain and pre-stressed or toughened glass. Extensive research and service
experience has shown that these materials are very reliable and cost effective
for a majority of outdoor applications. However, since early sixties, alternative
materials namely polymers have emerged and presently are being used
extensively for a variety of outdoor insulator applications. Polymeric
insulators are increasingly being used in both the distribution and transmission
voltage ranges and are steadily capturing a wider share of the market.
Initially, polymeric insulators (also called composite or non-ceramic
insulators) were considered as replacement for porcelain and glass for special
applications such as areas with high incidences of vandalism, urban locations
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 13/104
2
tracking and erosion of polymer sheds, chalking and crazing of sheds which
lead to increased contamination collection, arcing and flashover, bonding
failures and electrical breakdowns along the rod-shed interface, corona
splitting of sheds and water penetration which lead to electrical breakdown.
Today polymeric insulators are in use on lines operating up to 765 kV.
However, they are more popular on transmission levels from 69 kV through
345 kV. A recent worldwide survey showed that there are thousands of
polymeric insulators in service at all voltage levels.
Fig. (1.1) shows the results of a CIGRE survey done in 2000 to
investigate the global distribution of composite insulators at voltage levels
above 100 kV [1]. Middle East is one of the regions where composite
insulators are gaining ground.
10
100
1000
10000
100000
1000000
N o
o f I n s u l a
t o r s
SiR
Others
Total
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 14/104
3
1.1 POLYMER INSULATORS: ADVANTAGES AND
DISADVANTAGES
1.1.1 Advantages
The primary impetus for polymeric insulators increased acceptance by
the usually cautious electric power utilities as discussed before, is their
substantial advantage compared to inorganic insulators which have primarily
been porcelain and glass. One of their major advantages is their low surface
energy and thereby maintaining a good hydrophobic surface property in the
presence of wet conditions e.g. fog, dew and rain. Other advantages include:
(1) Light weight which results in a more economic design of the towers or
alternatively enabling to upgrade the voltage of existing systems
without changing the tower dimensions. An example of this was a case
in Germany where the voltage was increased from 245 to 420 kV and
in Canada where two 115 kV, 50 km long lines were up-rated to 230
kV using horizontal polymer insulators on the same towers. The light
weight of the composite insulator strings also permits an increase in the
clearance distance between the conductor to ground and an increase in
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 15/104
4
light weight of the composite insulators also obviates the need to use
heavy cranes for their handling and installation and this saves on cost,
(2) A higher mechanical strength to weight ratio which enables the
construction of longer spans of towers,
(3) Line post insulators are less prone to serious damage from vandalism
such as gunshots which cause the ceramic insulators to shatter and drop
the conductor to the ground,
(4) Much better performance than ceramic insulators in outdoor service in
the presence of heavy pollution as well as in short term tests,
(5) Comparable or better withstand voltage than porcelain and glass
insulators,
(6) Easy installation thus saving on labor cost, and
(7) The use of composite insulators reduces the maintenance costs such as
of insulator washing which is often required for ceramic and glass
insulators, in heavily contaminated environment.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 16/104
5
1.1.2 Disadvantages
The main disadvantages of composite polymeric insulators are:
(1) They are subjected to chemical changes on the surface due to
weathering and from dry band arcing,
(2) Suffer from erosion and tracking which may lead ultimately to the
failure of the insulator,
(3) Life expectancy is difficult to evaluate, and
(4) Faulty insulators are difficult to detect.
1.2 TYPES OF INSULATING MATERIALS
In fact, there are hundred of insulation materials which are used
in the electrical power industry. All such materials can broadly be classified
into different categories: such as gases, liquids, solids, vacuum and
composites [2,3].
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 17/104
6
A summary of insulation materials used in electrical networks is shown
in Fig. (1.2).
Materials
Conductor Insulator Semiconductor
CompositeVacuumSolidsLiquidsGases
Organic Polymer Inorganic
Thermoplastic Thermosetting
Nylon Polyethylene Epoxy resinsCrosslinked
polyethylene
Polystyrene Polypropylene Phenolics
Urea
Formaldehyde
PolycarbonatePolyvinyl
chloride Melamine Elastomers
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 18/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 19/104
8
CHAPTER 2
LITERATURE REVIEW AND DATA COLLECTION
2.1 INTRODUCTION
Polymeric insulators are being accepted increasingly for use in outdoor
installations by the traditionally cautious electric power utilities worldwide.
They currently represent 60 to 70% of newly installed HV insulators in North
America [1]. The tremendous growth in the applications of non-ceramic
composite insulators is due to their advantages over the traditional ceramic
and glass insulators. These include light weight, higher mechanical strength to
weight ratio, resistance to vandalism, better performance in the presence of
heavy pollution, in wet conditions and comparable or better withstand voltage
than porcelain or glass insulators. However, because polymeric insulators are
relatively new, the expected lifetime and their long-term reliability are not
well known and therefore are of concern to users. Additionally they might
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 20/104
9
2.2 BASIC POLYMERIC INSULATORS COMPONENTS
The basic construction of a polymer insulator for overhead line
applications consists of a core, weather sheds, and metal end fittings as shown in
Fig. (2.1).
Fig. (2.1): Components of polymer insulator.
2.2.1 Core
The core of a non-ceramic insulator has the dual burden of being the
main insulating part and of being the main load-bearing member, be it in
suspension, cantilever, or compression modes. For suspension and line post
insulators, the core consists of axially aligned, glass fiber-reinforced resin
containing 70 to 75% by weight of glass fiber. The fiber diameter ranges from
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 21/104
10
The end seal is considered to be the most important element of the
design of a non-ceramic insulator. Field failures have occurred due to brittle
fracture of the fiberglass rod as a consequence of the breach of the end seal,
thereby allowing the rod to come into contact with atmospheric pollutants and
moisture. Tracking of the fiberglass rod leading to failure has also been
observed in non-ceramic insulators.
Non-ceramic insulator end seals have three basic types: glued, friction,
and bonded types. Glued type seals that are made using a sealant material have
not proven to be permanent, generally because of poor adhesion. Friction-type
seals in which the sleeved core fits into the hardware are quite effective, as
long as the dimensional tolerances are maintained, and do not cause any
problems, provided that no movement of the fitting occurs. End seals that are
made by molding the sleeved core material onto the end fitting are by far the
best because of the better physical bond obtained during molding.
2.2.2 Weather Sheds
Sheds made from various non-ceramic materials for electrical
applications are shaped and spaced over the rod in various ways to protect the
rod and to provide maximum electrical insulation between the attachment
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 22/104
11
However, only the elastomeric materials have shown success in outdoor
electrical insulation applications, with silicone elastomer meeting all of the
requirements for long-term performance in practically all environments.
The polymers have the ability to interact with pollutants and reduce the
conductance of the pollution layer. This is illustrated in Fig. (2.2) [3]. The
important characteristic of the polymeric insulator which controls the
conductance is due to hydrophobicity (or water repellency) of its surface. On a
hydrophobic surface, water drops bead up and do not wet the surface
completely. This reduces the leakage current and the probability of dry band
formation, which leads to a higher flashover voltage. It has been observed that
the hydrophobicity is maintained in silicone rubber materials even after many
years in service, and it is this attribute that is responsible for the superior
contamination performance of silicone rubber family of materials when
compared to other polymers. The recovery of hydrophobicity is mainly due to
(i) a diffusion process, in which the low molecular weight polymer chains
migrate to the surface thereby forming a thin layer of silicone fluid and (ii)
reorientation of surface hydrophillic groups away from the surface. These
processes are temperature dependent and higher temperature causes their more
rapid recovery.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 23/104
12
Fig. (2.2): Surface resistance of bare and silicone-coated porcelain insulators
under salt fog conditions [3].
It has been reported that Ethylene Propylene Diane Monomer (EPDM)
and silicone elastomeric materials containing a minimum of 70% by weight of
hydrated alumina that are in use by most of manufacturers are favored for
weathersheds with silicone rubber showed the best performance over all other
types [3]. Failures of some first generation polymeric insulators with epoxy
resin weathersheds have been attributed to depolymerization by the hydrolysis.
Depolymerization refers to the destruction of the molecular structure of the
polymer material. Hydrolysis is the result of a chemical reaction, which takes
place between the ions of water and the free ends of polymer's chemical chain,
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 24/104
13
curing of the resin is uneven. Circumferential cracks between sheds sometimes
develop during storage of the insulator because of the locked-in stresses.
However, more often the cracks develop in service as the stresses are
aggravated by low temperature and line tension. The cracks extend down to
the core, thereby exposing the core to the moisture. Elastomers are the best
weathershed materials, as they do not contain locked-in mechanical stresses
from the curing process. Also, elastomers are preferred at low temperatures
where impact resistance is important.
Another problem that surfaced early in the experience of first
generation designs was the effect of outdoor weathering on weathersheds.
Weathering affects all polymer materials to some extent and being a natural
phenomenon includes the effects of heat, humidity, rain, wind, contaminants
in the atmosphere and ultraviolet rays of the sun. Under such conditions, the
weathersheds of polymer insulators may permanently change physically by
roughening and cracking and chemically by the loss of soluble components
and by the reactions of salts, acids and other impurities deposited on the
surface. Surface becomes hydrophilic and moisture can more easily penetrates
into the volume of the weather sheds.
2 2 3 H i
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 25/104
14
employ a sheath made of insulating material between the weathersheds and the
core. This sheath is part of the housing.
2.2.4 End Fittings
End fitting transmit the mechanical load to the core. They are usually
made of metal.
2.3 INSULATOR TYPES
Three types of insulators are in common use i.e. the suspension/dead-end
type, line post insulators and Guy strain type insulator, as shown in Figs. (2.3)
and (2.4). The only significant differences among these are in the design of the
attachment hardware and in the size of the core, which is much larger for post
insulators.
15
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 26/104
15
Fig. (2.4): Line post type polymeric insulators (~15 kV).
(a) Dead-End/Suspension Type Insulators
This type of insulator is used where line conductor weight subjects the
insulator core to tension forces. The dead-end / tension insulator horizontally
supports the line conductor whereas suspension insulator vertically supports the
line conductor as shown in Fig. (2.5). Both are subject to tensile and torsional
loads.
16
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 27/104
16
Fig. (2.5): Photographs of the lines with suspension type insulators.
(b) Line Post / Station Post Insulators
The line post/ station post insulators horizontally or vertically support
the line conductors as shown in Fig. (2.6). Such an insulator is subjected to
tensile, cantilever and compressive loads.
17
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 28/104
17
(c) Guy Strain Insulators
The guy-strain insulators, insulate or isolate the guy wire for corrosion
protection, higher insulation level, clearances for maintenance during normal
operation, or safety to the public or others. It is subjected to tensile and
torsional loads. Fig. (2.7) shows this design.
Fig. (2.7): Guy strain type polymeric insulators.
2.4 WEATHERSHEDS OF POLYMERIC MATERIALS
Polymeric insulators have been in use in outdoor service for about fifty
years. They cover a wide range of materials and formulations. These include
bisphenol epoxy resins which were used commercially for indoor applications
18
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 29/104
18
Polymeric insulators for transmission lines began to be manufactured in
Europe and the USA in the mid 1975 and beyond. In 1977 Hydro Quebec in
Canada installed, on a 16 km section of 735 kV transmission line, 282
composite insulators made by three different manufacturers. This was
followed with a 120 km section using 1100 composite insulators. In addition,
the same power utility installed composite insulators on circuits of 120, 230
and 315 kV transmission lines. Different generic materials were used in the
manufacture of composite insulators. Initially they included Ethylene
Propylene Rubber (EPR) insulators which were made by Ceraver of France
(1975), Ohio Brass of USA (1976), Sedivar of USA (1977) and Lapp of USA
(1980). Silicone rubber (SiR) which was manufactured by Rosenthal of
Germany (1976) and Reliable of USA (1983); and cycloaliphatic epoxy by
Transmission Development of the UK (1977). Currently polymeric composite
insulators are manufactured in several countries worldwide.
Early experience with SiR included Room Temperature Vulcanized
(RTV)-SiR which had a low tear resistance of the weather-sheds.
Subsequently this was replaced with High Temperature Vulcanized (HTV)-
SiR. SiR composite insulators that were used in Germany in 1977 for upto
132 kV, and in 1979 for up to 245 kV [7].
19
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 30/104
19
composite insulators in place of glass. Ohio Brass (1986) introduced an alloy
of Ethylene Propylene Monomer (EPM) and SiR which was subsequently
changed to Ethylene Propylene Diene Monomer (EPDM) and SiR compound
in 1989 [8]. This alloy in a ratio of 10 (EPDM or EPM) to 3 (SiR) provided
the better mechanical properties, such as the stiffness of the EPDM and the
excellent hydrophobic characteristics of SiR. It was reported [8] that one
company has produced commercially with the alloys of EPDM and SiR over
2.5 million (M) distribution insulators, 0.1 M transmission class line post
insulators and 0.4 M suspension insulators which are currently installed in
power systems in different parts of the world. This gives a clear indication of
a wide acceptance of this blend of materials.
In some cases, power utilities are still reluctant to use composite
insulators because of the uncertainty of their long-term reliability, the
unknown life expectancy and the lack of adequate detection technology of
faulty insulators. However there are many organizations including
International Electrotechnical Commission (IEC) and IEEE which have been
attempting to address these problems and develop standards and test methods
for polymeric insulators.
h h h d id h i d l k di d
20
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 31/104
cycloaliphatic and aromatic epoxy resins. For low voltage, outdoor or indoor
applications, additionally high-density polyethylene (HDPE), polytetrafluoro
ethylene (PTFE), polyurethene (PUR), polyolefin elastomers and other
materials are also employed.
SiR was first produced in 1944. When the chain of the dimethyl
polysiloxane is very long (the number of the units of the siloxane is given as
several thousands, the silicone fluid becomes viscous with a gum-like
consistency from which SiR is made by adding fillers and curing agents.
In the compounding of the weather-sheds, fillers are added to enhance
the resistance to tracking and erosion as well as to provide improved
mechanical performance in tensile strength, abrasion resistance, tear strength,
modulus and to reduce flammability. Typical fillers used are alumina
trihydrate (ATH), Al2O3.3H2O or hydrated alumina, and silica (quartz powder)
[10], [11].
It has been reported that weather-sheds of porcelain insulators coated
with a thin layer of RTV-SiR which are being increasingly used world wide in
outdoor substations and on heavily contaminated insulators, gave similar
performance results as compared to SiR sheds [12]. Early guidelines for the
21
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 32/104
2.5 TESTING METHODS OF COMPOSITE INSULATORS
There are several national and international organizations attempting to
develop standards, guidelines and tests for composite insulators. These
include IEEE [14], IEC [15], CIGRE, American National Standards Institute
(ANSI) [16] and National Electric Manufacturers Association (NEMA) etc.
The IEC test [15] has been criticized as being more of a pollution test and not
being an aging test and therefore suggestions for improvements in the test
procedure were made [17], [18]. Most existing laboratory tests for accelerated
weathering are primarily useful for ranking of the compounded materials [71]-
[79].
Only tests in field stations and actual performance on power lines and
in outdoor substations could yield realistic results on outdoor service
performance of such insulations.
In accelerated aging tests in the fog chambers the specimens are
subjected to a simultaneous salt-fog and electric stress. The leakage current,
the pulse current and the accumulated charge are determined during a
prolonged test which can last up to 1000h [15], using an automatic data
acquisition system [19]. Often NaCl is added to the tap water (250 to 300
22
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 33/104
This is highly conductive and hydrophilic which could lead to premature
failure of the insulator being tested. An addition of CuCl2 to the water (1.2
g/m3) obviates the above mentioned problem [20].
The flow rate of the saline water forming the fog and the speed of the
fog droplets impinging on the surface of the polymer have a large effect on the
development of the leakage current even when the electric field stress is
maintained at the same level. The clean fog test method, in which steam is
employed, reflects the contamination in industrial areas away from the sea
coast. However, the dispersion in the test results among different laboratories
was reported to be very large using this method [21]. The clean fog test gives
a lower withstand voltage than in outdoor line performance, because the
insulators are more uniformly coated with the contaminants than in natural
conditions [22].
2.6 TEST RESULTS OF COMPOSITE INSULATORS
It has been shown that tests performed in six different laboratories
using salt-fog and tracking wheel on four different formulations of RTV-SiR
coatings applied to ceramic rods provided consistent results of the ranking of
the materials in terms of leakage current, cumulative charge flow and pulse
23
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 34/104
ultraviolet (UV) radiation on the aging was also included in that test. It was
found that the aging caused erosion and cracks were observed. The EPR
formulations generally performed better than the epoxy resins [24]. 72 kV and
230 kV composite rod insulators made of EPDM, EPM and HTV-SiR were
tested by aging with cement coating and clean fog, salt-fog and cement
coating and salt-fog. Substantial differences in the ability to withstand the
aging were found amongst the different insulator types [25].
It was concluded in [26] that the weather-shed design plays an
important role in the erosion and tracking of the insulator. HTV-SiR
insulators, with 27.6 mm per kV leakage path, showed that dry band arcing did
not develop in the presence of severe salt storms while with 17.3 mm/kV,
large leakage currents developed. A large power utility reported that during a
severe weather condition there were no flashovers in any of their 138 kV (377
units) and 230 kV (1430 units) SiR insulators while there were many
flashovers in their 138 kV and 230 kV EPDM and porcelain insulators [27].
HV porcelain and glass outdoor insulators coated with RTV-SiR
performed better than silicone grease under dc test under salt-fog where dry
band arcing was present [28]. Other metals such as aluminum, stainless steel,
b d i d [29] b f d i f b h
24
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 35/104
surface for improving the contamination performance of outdoor bushings and
ceramic and glass insulators. Full length porcelain multi-core insulators
coated with RTV-SiR had higher flashover voltages than uncoated porcelain
insulators when contamination was present on their surface in the range of
Equivalent Salt Deposit Density (ESDD) of 0.07 to 0.16 mg/cm2.
Fig. (2.8): Dependence of the withstand voltage on (equivalent salt deposit
density) ESDD in SiR and porcelain insulators [3].
SiR insulators had been evaluated in outdoor conditions for nine years
and were found to remain water repellent when either energized or un
25
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 36/104
insulators were almost comparable to the porcelain insulators. The withstand
voltage of SiR insulators decreased with increasing ESDD as shown in Fig.
(2.8).
The withstand voltage of SiR also decreased with increasing non-
soluble deposit density (NSDD) in the range 0.1 to 5 mg/cm2 and increased
with increasing length of the insulator [3].
In another investigation, the ratio of the leakage distance to the surface
area of the insulators was kept constant at 5.6 * 10-3
mm-1
±10% and the
average electric stress was set as that used in practice [26]. It was reported
that the leakage current decreased when this ratio was increased. In RTV-SiR
the leakage current in salt-fog tests increased with increasing electric stress
[33], [34].
Testing SiR on a tracking wheel using a salinity of 1.33 mS/cm showed
that erosion was more severe with positive dc than with ac [35]. The erosion
was confined to the vicinity of the electrodes with dc but it covered a larger
area with ac. There was a larger loss of material with dc than with ac and the
loss was larger at the higher electric field, using 0.83 and 0.5 kV/cm [35].
Studies using electron spectroscopy for chemical analysis (ESCA) on
26
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 37/104
SiR the changes in these elements were not significant. On the surface of SiR
the content of ATH was reduced after 5 yr on the lines. Similar observations
were reported on SiR and EPDM insulators which had been energized at 300
kV. These results were independently confirmed using ESCA after tests in
salt-fog which also indicated a higher concentration of oxygen on the surface
than in the bulk of SiR [36]. It was suggested that this was due to the
crosslinking reactions of the silanols from dry band arcing. The oxidation of
the surface of EPDM and the EPDM/SiR alloy was evaluated by removing a
small amount of the polymer and analyzing it with Fourier Transform Infrared
(FTIR) and X-ray Photoelectric Spectroscopy (XPS) [37].
2.7 RANKING OF MATERIALS FOR OUTDOOR INSULATION
Polymeric materials perform differently according to the severity of the
tests. However, there appears to be a general consensus that HTV-SiR
insulators performed well under severe contamination and usually better than
ceramic insulators [38], [39], [40] and [41]. The withstand voltage of SiR,
EPR and epoxy resin in the presence of pollution was higher than that of
porcelain. Some EPDM insulators (34 kV to 500 kV) performed poorly and
showed punctured holes and damaged sheds. EPR performed better than
i [24] h fl h l f Si f
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 38/104
28
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 39/104
similar performance to that of RTV-SiR insulators which had been exposed to
HVAC and HVDC for many years in outdoor service [12].
2.8 EFFECT OF VOLTAGE POLARITY ON PERFORMANCE
The times to failure of HTV-SiR and EPDM rods at a fixed filler
concentration of either ATH or silica powder during testing in salt-fog, under
ac (60 Hz), and positive dc were similar [29]. For negative dc, the time to
failure was reduced by a factor of 4. The polymer rods were tested in the
vertical orientation and the dc voltage polarity refers to the top electrode. Fig.
(2.9) shows the differences in the cumulative charge in EPDM during
exposure to energized salt-fog for ac, positive and negative dc, and
comparison with HTV-SiR for ac and positive dc [29]. The cumulative charge
and therefore the leakage current was highest for negative dc, and it was
higher for EPDM than HTV-SiR under the same conditions.
At low conductivity (250 µS/cm) fog filled SiR samples had
substantially longer times to failure for ac, positive and negative dc than the
correspondingly filled EPDM samples, while this order was reversed at high
conductivity salt-fog (1 mS/cm) [29].
29
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 40/104
Fig. (2.9): Cumulative charge in EPDM and HTV-SiR rods during exposure
to energized salt-fog showing the differences between ac (60 Hz),
+dc and –dc. Conditions: conductivity of the saline water forming
EPDM (−dc)
EPDM (ac and =dc)
3 SILICONE RUBBER (−dc)
4
SILICONE RUBBER (ac and +dc)
30
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 41/104
2.9 PROPERTIES OF POLLUTION ON POLYMERIC
INSULATORS
It was reported that both sea and industrial pollution produce uniform
contamination layers on the surface of SiR insulators [49]. The salt-fog
produced for un-energized insulators an ESDD of 0.02 mg/cm2 after exposure
to 3 mS/cm salt-fog for ≤2 hours, and 0.02 to 0.05 mg/cm2 when energized at
0.4 kV for 10 and 120 minutes, respectively [49]. SiR insulators from
transmission lines after a number of years in service had typically 8 µm
(ESDD at 0.05 mg/cm
2
) to 23 µm thick of contaminants (ESDD at 0.026
mg/cm2). The nature of the contamination was either carbon dust on the
insulators removed from lines near a highway or dust and bird droppings from
agricultural areas [49].
The dc flashover voltage of SiR contaminated with kaolin
(composition: SiO2 – 46%, Al2O3 – 37%, Fe2O3 – 0.9% [50]), was 15% lower
than with Tonoko (composition: SiO2 – 57~65%, Al2O3 – 14~30%, Fe2O3 –
2~6% [51]), and with Aerosil was lower than both because it absorbed water
and formed a much thicker layer on the surface. After 7 years of service near
the coast no significant difference in ESDD was observed on composite and
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 42/104
32
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 43/104
2.10 ARTIFICIAL CONTAMINATION ON POLYMERIC
INSULATORS
Because of the initial hydrophobic nature of polymeric insulators it is
rather difficult to apply artificial contaminants and to ensure that they adhere
to the surface for the duration of the test. A method of application of artificial
contamination on SiR which was reported to provide a uniform contamination
layer was discussed in [55].
It employs powdered Tonoko [50] which is deposited after spraying the
surface with a fine mist of water droplets and allowing it to dry. Then the
deposited Tonoko is washed off with running tap water. The insulator is then
immersed in the slurry of contaminants and dried. This method was reported
to have been applied successfully to SiR and EPDM insulators [55].
Attempts have been made to coat polymeric insulators with a pollution
layer for testing purposes by first destroying the hydrophobic nature of the
surface by sand blasting or adding wetting agents. The usual procedure to coat
insulators is to contaminate the insulator with a slurry containing water and
NaCl and an insoluble material which is usually kaolin. The insoluble
material content is typically 40 g/l [22]. The slurry is allowed to dry on the
33
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 44/104
2.11 AGING OF POLYMERIC INSULATORS AND MECHANISMS
OF FAILURE
Gorur et al. [41] suggested that aging of polymer insulators in outdoor
service starts with the loss of hydrophobicity due to weathering and then dry
band arcing follows, and in the case of SiR, with a reduction of low molecular
weight (LMW) fluid on the surface. This leads to increased current, increased
surface roughness, depolymerization of the top surface layer, changes in the
structure due to crystallization of the polymer and clustering of the filler and
then tracking and/or erosion failure. X-ray diffraction studies indicated an
increase in the crystallinity of the SiR with aging in salt-fog and dry band
arcing [28].
The difference in the flashover voltage performance for the same
ESDD was attributed to the difference in the solubility of the contaminants.
The ambient temperature has a significant influence on the solubility of the
salts and therefore on the contamination flashover voltage. The solubility of
the salt depends on several factors, the most important of which are
temperature, pH (hydrogen potential) and the presence of strong ionic
components. In outdoor conditions near the coast, highly soluble salts such as
C ( O ) O Cl C Cl C1 Cl d l l bl l h
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 45/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 46/104
36
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 47/104
2.12 AGING FROM EXPOSURE TO ULTRAVIOLET RADIATION
Polymeric materials employed to fabricate composite insulators contain
small amounts of compounds such as ZnO2 and TiO2 which absorb UV
radiation and thus protect the material against damage from the radiation of
the sun rays.
SiR filled with ATH (45 to 54%), EPR filled with ATH (56 to 61%)
and SiR filled with silica quartz powder (46 to 50%) were exposed to UV
radiation for 1000 hours and tested on a tracking wheel [62]. The test results
indicated that UV radiation had no effect on the tracking endurance of the
polymers.
Subjecting HTV-SiR, EPDM and EPM to multi-stresses of electrical
(0.5 to 1 kV/cm) and/or mechanical and to UV radiation showed that there was
a synergetic effect between exposure to UV irradiation and mechanical stress.
However, a synergism was not present between UV radiation and electrical
stress when discharges were absent from the surface. When EPDM had no
UV or thermal stabilizers, the advancing contact angle decreased with
increasing exposure time to UV. FTIR spectra showed that the absorbance of
the carbonyl (C=O), the alcohol (C-O-H) and hydroperoxide (C-O-O-H) peaks
increased with increasing time of exposure to UV and there was a correlation
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 48/104
38
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 49/104
Visual inspections of composite insulators were carried out every two
years since 1981 on the 735, 315, 230 and 120 kV lines, Hydro Quebec in
Canada [65]. It was found that most of the problems with composite
insulators could be found by visible inspection from the towers and these
presented the largest percentage of failures. An inspection from the ground
using binoculars was not sufficient.
Electric field testing permitted the detection of non-visible defects
which had occurred at the interface between the fiberglass rod and the
covering polymeric material. It was reported that in the area of a defective
shed there was a decrease in the longitudinal field along the string [65]. Fig.
(2.11) shows the effect on the electric field along the insulator surface when a
defect is present in one of the sheds of an EPDM insulator.
Shed No
16 cm
32 cm
none
antistatic 32 cm
E l e c t r i c F i e l d ( k V / m )
39
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 50/104
2.14 EFFECT OF RAIN ON ELECTRIC FIELD DISTRIBUTION
The axial field distribution along a porcelain post insulator coated with
RTV-SiR changed when artificial rain was applied to it [66]. The sensitivity
of the field distribution and the discharge activity to the precipitation rate of
the rain (0.4 and 1.6 mm/min) was small for conductivities of 50 and 250
µS/cm at low voltage. At high conductivity of the rain and high precipitation
rate, higher fields at the upper sheds were observed [66].
In artificially contaminated SiR and EPR insulators, the phenomenon of
sudden flashover without a prior leakage current was investigated. The
sudden flashover was attributed to the high electric field at the edges of the
dried high resistance regions. When sufficient recovery time was allowed,
SiR did not experience sudden flashover while EPR insulators did. It was
reported that in rain tests, hydrophobic surfaces prevent an increase in the dry
zones and significantly reduce the radial field strength.
2.15 HYDROPHOBIC PROPERTIES AND FLUID DIFFUSION TO
THE SURFACE
In heavily polluted areas, contaminants gradually build up on the
surface of insulators into a continuous layer SiR insulators were reported to
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 51/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 52/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 53/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 54/104
44
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 55/104
A serious problem with composite insulators, however, is their
sensitivity to atmospheric and electrical stresses in outdoor applications. In
contrast to traditional ceramic insulators, composite insulators may be
damaged under combined electrical and atmospheric stress, leading to a
reduction in their useful life. There exist thousands kilometers of overhead
transmission and distribution lines extending through different types of terrain
and environments in the Kingdom of Saudi Arabia. Vast areas of desert, often
adjacent to the sea characterize the Kingdom's climatic conditions and
geography. This type of severity and diversity affects the insulators to a large
extent.
It is clear from this brief review that the long term performance of
polymeric insulators depends on the environmental (specially temperature and
the UV radiations) beside the operating stress levels and need careful
evaluation using laboratory testing as well as field experience history of other
users. This project proposed initial studies towards this goal.
45
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 56/104
CHAPTER 3
EXPERIMENTAL SETUP AND PROCEDURES
3.1 SIGNIFICANCE OF ACCELERATED AGING OF POLYMERIC
INSULATORS
In order to know the satisfactory resistance to weathering, it is
necessary to understand weather factors, and what they can do to various
materials. Climatic conditions around the world are of such diversity that
optimum and economic product design for outdoor use must reflect these
climatic differences. A more realistic, and still reliable design, may be
obtained on the basis of an overall understanding of the range of weather
variables at a specific location under consideration. Such knowledge is needed
both by the designer as well as practicing engineer.
In the world, with widely varying climates and weather conditions, an
insulator in service in the west will experience entirely different climatic and
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 57/104
47
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 58/104
3.2 ACCELERATED AGING CYCLE
For the accelerated aging process as per IEC standard 1109 [15] (for the
non-ceramic (polymeric) composite insulators) tests were carried out on
polymeric insulators made from Silicon Rubber (SiR) and Thermoplastic
Elastomer (TPE), the various stresses to be applied in a cyclic manner, as per
IEC 1000 hours test standard are:
• solar radiation simulation.
• dry heat.
Furthermore, temperature variations may cause some degree of
mechanical stress, especially at the insulator interfaces and also give rise to
condensation phenomena which are repeated several times in the course of a
cycle.
An aging cycle including electrical, temperature and UV radiation
stresses used is shown in Fig. (3.1). Here, each cycle lasts for 24 h and a
programmed change takes place every 6 hours. During the time when heating
is out of operation, the insulators are cooled down to ambient temperature. As
48
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 59/104
Heating (57°C)
Radiation (1 mW/cm²)
Voltage (28 kV)
Time (hours)2~8 AM 8 AM ~
2 PM
2~8
PM
8 PM ~
2 AM
In Operation Out of operation
Fig. (3.1): Accelerated aging cycle.
3.3 DESIGN OF ACCELERATED AGING TEST CHAMBER
For the accelerated aging of nonceramic insulators, as per IEC standard
[15] as discussed in sections 3.1 and 3.2, a wooden chamber was constructed
in our laboratory. The dimensions of the chamber are approximately 120cm
(wide) x 120cm (high) x l80cm (long). Up to 12 post insulators of 28 kVL-L, or
an equivalent number of suspension dead end insulators, can be subjected to
accelerated aging cycle in this chamber. Higher voltages are possible with
slight modifications in the chamber. A schematic diagram of the chamber is
shown in Fig. (3.2a) whereas photo of front view of the chamber with 28 kV
suspension insulators in place is shown in Fig. (3.2b). It is worth mentioning
49
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 60/104
Fig. (3.2a): Schematic diagram.
50
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 61/104
In this chamber, the following instruments/facilities are installed:
i)
UV-A lamps
ii) Polymeric insulator
iii) Electric Heater
iv) Timers
v)
Blower/fan
vi) Power Transformer
vii) UV light meter
i) UV Radiation/ UVA Lamps
UVA lamps are especially useful for comparing different types of
polymers whereas UVB (315-280 nm) and UVC (100-280 nm) are found in
the outer space filtered by earth's atmosphere; germicidal. Because UVA
lamps do not have any UV output below the normal cut-off of 295 nm. The
UVA-340 lamps provide the best possible simulation of sunlight in the critical
short wave length region from 365 nm down to the solar cut-off of 295 nm.
Its peak emission is at 340 nm.
In the chamber, the ultraviolet (UV-A) radiation system duplicates
exposure in the portion of the solar spectrum (300–340 nm) that is responsible
f i f i i l t UV A l Th t d d b
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 62/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 63/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 64/104
54
C B
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 65/104
C B
220 V, ac
Test
Insulator
220 V / 100 kV
Fig. (3.5b): Transformer connections used for testing.
iv) Heating Arrangement
Since temperature affects the aging of polymeric materials, heat is the
most important stress since the aging rate is accelerated by some factor for
each degree rise in temperature [80]. A 2000W tubular heater is used to
develop heat. A PC based ON-OFF control system is used to maintain a
relatively stable temperature in the chamber. The heat generated by the heater
is uniformly distributed by an axial blower installed inside the chamber. In the
central region of Saudi Arabia, the maximum daytime temperature which
remains almost stable from 1 PM to 4 PM varies during summer months in a
range of 42 ~ 50°C, with around 46°C being the average value. This situation
lasts for six months (May ~ October). To simulate this temperature profile,
the thermostat was set at a temperature of 57°C. This 57°C is selected such
55
This 11°C is also considered to play role in accelerated aging process. Fig.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 66/104
(3.6) shows the actual variations of temperature on the porcelain and polymer
insulator’s surfaces as well as the UV-A radiation level in Riyadh.
Actual temperature and UV-A radiation level
10
20
30
40
50
60
4 5 6 7 8 9
Months
T e m p r a t u r e ( C )
10
20
30
40
50
60
U V r a d i a t i o n l e v e l ( W / m 2 )
Amb. Temp
Insulator surface temp.(Poreclain)
Insulator surface temp.
(Polymer)
UVA radiation level
(W/m2)
Fig. (3.6): Temperature variation on insulator surface (under no load) and
UV-A radiation level in the Central region of Kingdom (Riyadh).
As per IEC standard 1109 [15] for the accelerated aging cycle, the
temperature rise & fall in the chamber should take place only in 15 minutes.
For this purpose the temperature rise and fall data were measured in the
chamber as well as on the surface of the polymer insulators, using K-type
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 67/104
57
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 68/104
Fig. (3.8): Timer (TM-30A, Kawamura TS, Japan).
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 69/104
73
while the present investigation shows that the surface temperature of
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 70/104
these insulators can increase by 5 to 11 °C above the prevalent ambient
atmospheric temperatures (42 – 50 °C).
2. The SEM analysis revealed that SiR based insulators experience much
higher surface roughness due to aging whereas negligible surface
roughness was observed in case of aged TPE insulators. Similarly the
XPS analysis exhibit much higher decomposition of SiR material than
TPE polymer.
3. Dielectric response of TPE types of insulators also indicates that these
units outperform the SiR type insulator when subjected to the
accelerated aging tests adopted in these tests.
5.2 RECOMMENDATION FOR FUTURE WORK
Since the central region of Saudi Arabia is almost one of the highest
UV-irradiated terrains in the world coupled with high atmospheric
temperatures, therefore, the adoption of polymeric insulators requires careful
selection. In this context, all popular type of insulators including the newly
introduced ones need to be thoroughly and systematically investigated not
di t IEC t l b t d difi d i t l th t t l
58
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 71/104
CHAPTER 4
RESULTS AND DISCUSSIONS
After completion of the accelerated aging test of the SiR and TPE
composite insulators, as per modified IEC 1109 procedure as discussed in
Chapter 3 of this report, various electrical, SEM based optical and visual tests
were performed and the results are summarized and discussed next.
4.1 LIGHTNING IMPULSE WITHSTAND TESTS
In order to compare the effect of accelerated aging, all the laboratory
aged as well as the control (new) insulator samples of each type (SiR and
TPE) were subjected to impulse voltage applications. The impulse generator
was adjusted to produce standard Lightning Impulse (LI) waveforms
(1.2/50µs) of both positive and negative polarities. Fig. (4.1) shows the
positive lightning impulse voltage wave whereas the schematic diagram of this
test set up is shown in Fig. (4.2). The voltage was increased in small steps of
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 72/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 73/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 74/104
62
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 75/104
100
105
110
115
120
125
130
135
140
Dry (SiR) Wet (SiR) Dry (TPE) Wet (TPE)
F l a s h o v e r
v o l t a g e ( k V )
Insulator (aged)
Insulator (New)
Fig. (4.5): Flashover voltage under 60-Hz AC voltage.
4.3 SCANNING ELECTRON MICROSCOPY (SEM) OF SAMPLES
Small samples (2 mm × 2 mm) were removed from the high voltage
end of each insulator and their surface analysis was performed using type
JEOL JSM-6360-A (Japan) Scanning Electron Microscope (SEM). The
analyses were made in high vacuum mode in order to avoid sample charging.
Secondary Electron Imaging (SEI) was performed to study the surface
morphology at an accelerating voltage of 20kV.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 76/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 77/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 78/104
66
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 79/104
Figs. (4.7) and (4.8) show the peaks from the photoionization of oxygen
(O15) and carbon (C15) at 525 eV and 277 eV, respectively. It is also evident
from these spectrums that % share of carbon and oxygen has rapidly increased
from 17.97% and 34.06% to 20.13% and 45.81% respectively in case of SiR
(Fig. 4.7) and from 45.31% and 34.58% to 47.29% and 39.30%, respectively in
case of TPE (Fig. 4.8), due to exposure to UV-radiation and heat. The increase
of C could be from the scission of CH3 bonds and the formation of various
products due to reaction between C and O2 during oxidation.
In these samples, the presence of oxygen detected by XPS both in SiR
and TPE on the new and aged surfaces is attributed to the availability of oxygen
from the additives or from the moisture in the atmosphere or due to oxidation of
the rubber during manufacturing [85]. Peaks of Al are also observed in all
samples as shown in Figs. (4.7) and (4.8). Slight traces of Ti were observed in
case of TPE (new) as shown in Fig. (4.8a) which disappeared due to aging where
instead some traces of Vanadium were detected. This could be due to additives
or any other decomposition process in the material during aging process.
67
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 80/104
(a) SiR insulator (New)
68
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 81/104
(a) TPE insulator (New)
69
Table (4.1) shows the percentage atomic concentration of C, O, Si, and Al
elements in all the tested samples.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 82/104
Table (4.1): Concentration (%) of elements detected by XPS.
SiR TPEElements
New Aged New Aged
C (0.277 keV) 17.97 20.13 45.31 47.29
O (0.525 keV) 34.06 45.81 34.58 39.30
Al (1.486 keV) 21.69 17.95 17.29 13.08
Si (1.739 keV) 26.28 16.11 -- --
Ti (4.508 keV) -- -- 2.88 --
V (4.949 keV) -- -- -- 0.33
The aged surfaces have different physical, chemical and electrical
properties due to different chemical compounds at different binding energies
(compared to new) because of weathering/photo-oxidation, as observed from
XPS results. This was corroborated by the hydrophobicity change and the
nature of the SEM results observed.
Service experience has indicated that sunlight is an important factor in
70
presence of an allylic group in the polymer backbone. Mere sunlight is not
enough for causing deterioration. Chromophoric groups are also necessary to
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 83/104
absorb the incident radiation and transfer energy to the bond. In polymers,
chromophoric groups are present in the unsaturated structures, such as car-
bonyl groups which are formed during manufacturing. The energy of a photon
of light is transferred to the molecule with resultant bond scission. The
resulting effects may include embrittlement, discoloration, and cleavage of
polymer chains. For this reason, polymers are filled with UV stabilizers and
antioxidants.
Oxidation reactions generally involve a free radical chain reaction.
Some of the main steps in this reaction are as follows:
Heat or Light
RH ⎯⎯⎯⎯⎯→ R (1)
R + O2 ⎯⎯⎯⎯⎯→ ROO (2)
ROO + RH ⎯⎯⎯⎯⎯→ ROOH + R (3)
Heat or Light
ROOH ⎯⎯⎯⎯⎯→ RO + OH (4)
2 ROOH ⎯⎯⎯⎯⎯→ RO + ROO + H2O (5)
71
Radicals are formed during initiation react with oxygen, leading to
chain reactions. The decomposition of hydroperoxides by heat or UV light
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 84/104
(reaction 4) causes formation of alkoxy and hydroxy radicals leading to chain
branching as evidenced by XPS results.
74
REFERENCES
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 85/104
[1]
J.R. Hall, "History and Bibliography of Polymeric Insulator's", IEEE
Trans. on PWRD, Vol. 8, pp. 376-385, 1993.
[2] S.H. Kim, E.A., Cherney and R. Hackam, "Hydrophobic Behavior of
Insulation Coated with RTV Silicone Rubber", IEEE Trans. on EI, Vol.
27, pp. 610-622, 1992.
[3]
R. Hackim, "Outdoor HV Composite Polymeric Insulators", IEEE
Trans. on DEI, Vol. 6, No. 5, pp. 557-585, 1999.
[4] J. Mackerich and M. Shah, "Polymers Outdoor Insulation Material, Part
I: Comparison of Porcelain and Polymer Electrical Insulation", IEEE
Electrical Insulation Magazine, Vol. 13, No. 3, pp. 5-11, 1997.
[5]
R.G. Houlgate and D.A. Swift, "Composite Rod Insulators for AC
Power Lines: Electrical Design at Coastal Station", IEEE Trans. on
PWRD, Vol. 5, pp. 1944-1955, 1990.
[6]
G.H. Vallancount, S. Carignan and C. Jeam, "Experience with the
Detection of Faulty Composite Insulators on HV Power Lines by
Electric Field Measurement Method" IEEE Trans on PWRD Vol 13
75
[7]
A. Hammer and A. Kachlar, "Insulation Systems for HVDC Power
Apparatus", IEEE Trans. on EI, Vol. 27, pp. 601-609, 1992.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 86/104
[8] T. Zhao and R.A. Bernstorf, "Aging Tests of Polymeric Housing
Material for Non-Ceramic Insulator", Electrical Insulation Magazine,
Vol. 14, No. 3, pp. 26-33, 1998.
[9] E.A. Cherney, "RTV Silicon – A High Tech. Solution for a Dirty
Insulator Problem", Electrical Insulation Magazine, Vol. 11, No. 6, pp.
8-14, 1995.
[10]
E.A. Cherney, G. Karady, W.T. Starr, F.J. Hall, G.E. Lusk, H. Dietz, L.
Pargamin and T. Moleff, "Minimum Test Requirements for Non-
Ceramic Insulators", IEEE Trans. on PAS, Vol. 100, pp. 882-890,
1981.
[11]
H. Jahn, R. Barsch, U. Kaltenborn and J. Kindersberger, "The
Evaluation of the Early Aging Period of Castings Made of Epoxy and
PUR Resins", IEEE CEIDP, pp. 698-701, 1998.
[12]
A.E. Vlastos and E. Sherif, "Experience From Insulators with RTV
Silicone Rubber Sheds and Shed Coating", IEEE Trans. on PWRD,
76
[13]
E.A. Cherney, G. Karady, R.L. Brown, J.L. Nicholls, T. Orbeck and L.
Paragamin, "Application of Composite Insulators to Transmission
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 87/104
Lines", IEEE Trans. on PAS, Vol. 102, pp. 1226-1234, 1983.
[14] IEEE Std. 1133-1988, "IEEE Application Guide for Evaluation Non-
Ceramic Materials for HV Outdoor Applications", 1988.
[15] IEC 1109-03, 1992, "Composite Insulators for AC Overhead Lines with
a Nominal Voltage Greater than 1000 V-Definitions, Test Methods and
Acceptance Criterion".
[16]
"American National Standard for Composite Suspension Insulators for
Overhead Transmission Lines Tests", ANSI-C29, 11, 1989.
[17] L. Gutman, R. Hartings, R. Matsouka and K. Kondo, "The IEC 1109,
1000 h Salt-Fog Test: Experience and Suggestions for Improvements",
Nordic Insulation Symps., Bergen, June 10-12, pp. 389-398, 1996.
[18] L. Gutman, R. Hartings, R. Matsuoka and K. Kondo, "Experience with
IEC 1109 1000 h Salt-Fog Aging Test for Composite Insulators", IEEE
Electrical Insulation Magazine, Vol. 13, No. 3, pp. 36-39, 1997.
[19] R.S. Gorur, E.A. Cherney and R. Hackam, "A Comparative Study of
77
[20]
F. Shmuck and B. Barsch, "Electrochemical and Microbiological
Phenomena During Accelerating Aging Tests of Polymeric Insulators",
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 88/104
Proc. of 8th
ISH, Yokohama, Japan, Paper 41.02, 1993.
[21] P.J. Lambeth and H.M. Schneider, "Clean Fog Test for HVAC
Insulators", IEEE Trans. on PWRD, Vol. 2, pp. 1317-1326, 1987.
[22] R.E. Carberry and H.M. Schneider, "Evaluation of RTV Coating for
Station Insulators Subjected to Coastal Contamination", IEEE Trans. on
PWRD, Vol. 4, pp. 577-585, 1989.
[23]
IEEE Dielectrics and Electrical Insulation Society in Outdoor Service
Environment Committee S-32-3, "Round Robin Testing of RTV
Silicone Rubber Coating for Outdoor Insulators", IEEE Trans. on
PWRD, Vol. 11, pp. 1881-1887, 1996.
[24]
S.M. de Oliverira and C.H. Tourreil, "Aging of Distribution Composite
Insulators Under Environmental and Electrical Stresses", IEEE Trans.
on PWRD, Vol. 5, pp. 1074-1077, 1990.
[25]
C.H. de Tourreil and P.J. Lambeth, "Aging of Composite Insulators:
Simulation by Electrical Test", IEEE Trans. on PWRD, Vol. 5, pp.
78
[26]
R.S. Gorur, E.A. Cherney and R. Hackman, "Polymer Insulator Profiles
Evaluated in a Fog Chamber", IEEE Trans. on PWRD, Vol. 5, pp.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 89/104
1078-1083, 1990.
[27] J.T. Burnham, D.W. Busch, J. and D. Renowden, "FPL's Christmas
1991 Transmission Outages", IEEE Trans. on PWRD, Vol. 8, pp. 1874-
1881, 1993.
[28]
R.S. Gorur, G.G. Karady, A. Jagota, M. Shah and B.C. Furumasu,
"Comparison of RTV Silicone Rubber Coatings under Artificial
Contamination in a Fog Chamber", IEEE Trans. on PWRD, Vol. 7, pp.
713-719, 1992.
[29]
R.S. Gorur, E.A. Cherney and R. Hackman, "The AC and DC
Performance of Polymeric Insulating Materials Under Accelerated
Aging in a Fog Chamber", IEEE Trans. on PWRD, Vol. 3, pp. 1892-
1902, 1988.
[30] R.S. Gorur, E.A. Cherney, C. de Tourreil, D. Dumora, R. Harmon, H.
Hervig, B. Kingsbury, J. Kise, T. Orbeck, K. Tanaka, R. Tay, G.
Toskey, D. Wiitanen, IEEE Dielectrics and Electrical Insulation
Society Outdoor Service Environment Committee S-32-3 Report
79
[31]
T. Sorqvist and A.E. Vlastos, "Outdoor Aging of Silicone Rubber
Based Polymeric Materials", IEEE Int. Conf. on Conduction and
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 90/104
Breakdown in Solid Dielectrics, pp. 401-405, 1998.
[32] G.N. Ramos, M.T.R. Campillo and K. Naito, "A Study on the
Characteristics of Various Conductive Contaminants Accumulated on
HV Insulators", IEEE Trans. on PWRD, Vol. 8, pp. 1842-1850, 1993.
[33]
S.H. Kim, E.A. Cherney and R. Hackman, "The Loss and Recovery of
Hydrophobicity of RTV Silicone Rubber Insulator Coating", IEEE
Trans. on PWRD, Vol. 5, pp. 1491-1499, 1990.
[34] S.H. Kim, E.A. Cherney and R. Hackman, "Electrical Performance of
Silicone Rubber Insulator Coating in Salt-Fog Chamber", IEEE CEIDP,
pp. 149-154, 1989.
[35]
T. Kuroyagi, H. Homma, T. Takahashi and K. Izumi", A Fundamental
Study on the Surface Degradation of Polymer Insulation Materials in
DC Voltage Application", IEEE CEIDP, pp. 682-685, 1988.
[36]
S.M. Gubanski, "Properties of Silicone Rubber Housing Coating",
IEEE Trans. on EI, Vol. 27, pp. 374-382, 1992.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 91/104
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 92/104
82
[51]
T. Tanaka, K. Naito and J. Kitagawa, "A Basic Study on Outdoor
Insulators of Organic Materials", IEEE Trans. on EI, Vol. 13, pp. 184-
193 1978
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 93/104
193, 1978.
[52] J.M. Fourmigue and M. Noel, "Testing Methods for Performance
Prediction of Outdoor Insulation Housings", IEEE CEIDP, pp. 451-
545, 1996.
[53]
X. Lin, Z. Chen, X. Liu, K, Chu, K. Morita, R. Matsouka and S. Ito,
"Natural Insulator Contamination Test Results on Various Sheds
Shapes in Heavy Industrial Contamination Areas", IEEE Trans. on EI,
Vol. 27, pp. 593-600, 1992.
[54]
S.M. Gubanski and J.G. Wankowics, "Distribution of Natural Pollution
Surface Layers on Silicone Rubber Insulators and Their UV
Absorption", IEEE Trans. on EI, Vol. 24, pp. 689-697, 1989.
[55] R. Matsuoka, H. Shinokubo, K. Kondo, Y. Mizuno, K. Naito, T.
Fujimura and T. Terada, "Assessment of Basic Contamination
Withstand Voltage Characteristics of Polymer Insulators", IEEE Trans
on PWRD, Vol. 11, pp. 1895-1900, 1996.
83
[57]
K. Naito, Y. Mizuno and W. Naganawa, "A Study on Probabilistic
Assessment of Contamination Flashover of HV Insulators", IEEE
Trans on PWRD Vol 10 pp 1378 1383 1995
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 94/104
Trans. on PWRD, Vol. 10, pp. 1378-1383, 1995.
[58] J.L. Goudie, M.J. Owen and T. Orbeck, "A Review of Possible
Degradation Mechanisms of Silicone Elastometers in HV Insulation
Applications", IEEE CEIDP, pp. 120-127, 1998.
[59]
A. De la O and R.S. Gorur, "Flashover of Contaminated Insulators in a
Wet Atmosphere", IEEE Trans. on DEI, Vol. 5, pp. 814-823, 1998.
[60]
W. Lampe, D. Wikstrom and B. Jacobson, "Field Distribution on an
HVDC Wall Bushing During Laboratory Rain Tests", IEEE Trans. on
PWRD, Vol. 6, pp. 1531-1540, 1991.
[61]
R.G. Niemi and T. Orbeck, "Test Methods Useful in Determining the
Wet Voltage Capability of Polymer Insulator Systems After Time
Related to Outdoor Exposure", IEEE Trans. on EI, Vol. 9, pp. 102-108,
1974.
[62]
E.A. Cherney and D.J. Stonkus, "Non-Ceramic Insulators for
Contaminated Environments", IEEE Trans. on PAS, Vol. 100, pp. 131-
84
[63]
E.L. de Mattos Mehl and C.H. de Tourreil, "Multiple Stress Aging of
HV Polymeric Insulation", IEEE Trans. on EI, Vol. 25, pp. 521-526,
1990
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 95/104
1990.
[64] R.W. Harmon, G.G. Karady, O.G. Amburgey, G. Gela, J. Hall, H.
Schneider, J.L. Burnham, J. McBride, L. Coffeen, N. Spaulding, T.
Carrera, Z. Szilagyi, J. Kuffel, R. Gemignani, J. Dushaw, R.
Humbridge, A. Bernstorf and J. van Name, "Electric Test Methods for
Non-Ceramic Insulators Used for Live Line Replacement", IEEE Task
Force on Electrical Testing of Polymer Insulators for Hot Line
Insulation, Transmission and Distribution Committee, IEEE Trans. on
PWRD, Vol. 12, pp. 965-970, 1997.
[65] G.H. Vaillancourt, S. Carignan and C. Jean, "Experience with the
Detection of Faulty Composite Insulators on HV Power Lines by the
Electric Field Measurement Method", IEEE Trans. on PWRD, Vol. 13,
pp. 661-666, 1998.
[66]
R. Hartings, "The AC Behavior of a Hydrophilic and Hydrophobic Post
Insulator during Rain", IEEE Trans. on EI, Vol. 9, pp. 1584-1592,
1994.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 96/104
86
[74]
R. Sundarajan, C. Pelletier, R. Chapman, and R. Nowlin, "Accelerated
Multistress Aging of Polymeric Insulators – A Case Study: Detroit",
IEEE CEIDP, pp. 641-644, 2000.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 97/104
IEEE CEIDP, pp. 641 644, 2000.
[75] Z. Tiam, H. Kawasaki, M. Hikita, "Degradation Effects and Insulation
Diagnosis of HV Polymeric Insulation under Accelerated Aging
Conditions", Proc. of 1998 Intl. Symposium on Electrical Insul.
Material, Toyobashi, Japan, pp. 627-630, 1998.
[76] H.M. Schneider, W.W. Guidi, G.W. Nicoholls, J.T. Burnham, J.F. Hall,
"Accelerated Aging Chamber for Non-Ceramic Insulators", 7th
ISH, pp.
199-202, 1991.
[77]
M. Ehsani, H. Borsi, E. Goekenbach, J. Morshedian, G.R.
Bakhshandeh, "Effect of Aging on Dielectric Behavior of Outdoor
Polymeric Insulators", IEEE ICSD, France, 2004.
[78] R. Sundarajan, A. Mohammed, N. Chaipait, "In service Aging and
Degradation of 345 kV EPDM T/L Insulators is a Coastal
Environment", IEEE Trans. on DEI, Vol. 11, No. 2, pp. 348-361, 2004.
[79] R. Sundarajan, Esaki, Sundarajan, A. Mohammed, J. Graves,
87
[80]
T.G. Gustavsson, S. M. Gubanski, H. Hillborg, S. Karlsson and U. W.
Gedde, "Aging of SiR under AC and DC voltages in Coastal
Environments", IEEE Trans. on DEI, Vol. 8, pp. 1029-1039, 2001.
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 98/104
, , , pp ,
[81] A. Suleiman. M. I. Qureshi, “Effect of Contamination on the Leakage
Current of Inland Desert Insulators” IEEE Trans. on DEI, Vol. 19, No.
4, pp. 332-339, 1984.
[82]
STRI Hydrophophobicity Classification Guide, 92/1, 1992.
[83] M. Amin, M. Akbar, R. Matsuska, "Effect of UV Radiation,
Temperature and Salt-fog on Polymeric Insulators", Proc. of 8th
ICPADM, pp. 611-615, 2006.
[84] A.E. Vlastos and S.M. Gusanseki, "Surface Structural Changes of
Naturally Aged Silicone and EPDM Composite Insulator", IEEE Trans.
on PWRD, Vol. 6, pp. 888-900, 1991.
[85] R. Sundarajan, E. Sundarajan, A. Mohammad and J. Grames, "Multi-
stress Accelerated Aging of Polymer Housed Surge Arresters Under
Simulated Coastal Florida Conditions", IEEE Trans. on DEI, Vol. 13,
No. 1, pp. 211-228.
88
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 99/104
Annex – I
89
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 100/104
90
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 101/104
Annex – II
91
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 102/104
King Saud University, Please return to: Attn: Dr. Yasin Khan
Research Center Electrical Engg. Department
Survey Form Project # 18 / 426 Fax No.: 01-467-6757
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 103/104
I: Polymeric Insulators
Voltage Class Type *Manufacturer
/ Supplier
Material of
the polymer
insulator
No. of years
in service
No. of failures
occurred
Reasons of
failure
13.8 kV
33 / 34.5 kV
* Dead end type /Suspension type /
Line post /Guy strain Insulator
II.
What is the intensity of the solar / ultraviolet (UV) radiations in (mW/cm2)?
III. Any investigative studies carried out internally by SEC on the performance and pollution related problems of polymer insulators inuse?
King Saud University, Please return to: Attn: Dr. Yasin Khan
Research Center Electrical Engg. Department
Survey Form Project # 18 / 426 Fax No.: 01-467-6757 1. Environmental Data of Riyadh
7/23/2019 polymer insulators
http://slidepdf.com/reader/full/polymer-insulators 104/104
1. Environmental Data of Riyadh
Year Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.
2001 Max. Ambient Tem . C°
Min. Ambient Temp. (C°)
Humidity (%)
Rainfall (mm)
2002 Max. Ambient Temp. (C°)
Min. Ambient Temp. (C°)
Humidity (%)
Rainfall (mm)
2003 Max. Ambient Temp. (C°)
Min. Ambient Temp. (C°)Humidity (%)
Rainfall (mm)
2004 Max. Ambient Temp. (C°)
Min. Ambient Temp. (C°)
Humidity (%)
Rainfall (mm)
2005 Max. Ambient Temp. (C°)
Min. Ambient Temp. (C°)
Humidity (%)
Rainfall (mm)
II. What is the month- wise Maximum intensity of the solar ultraviolet (UV) radiations in (mW/cm2) in Riyadh?