AProject Report

On“COUPLED FIELD FINITE ELEMENT ANALYSIS OF

DISC TYPE INSULATOR ASSEMBLY”

Submitted to

Sant Gadge Baba Amravati University

In Partial Fulfillment of the Requirements

For the Degree of

Bachelor of Engineering In

Mechanical Engineering

Submitted by

Mr. Swagat S. Giri Mr. Kaustubh S. Nerekar

Mr. Aniket T. Shisode Miss. Prachi S. Giri

Mr. Sagar . Gawande

FINAL YEAR MECHANICAL ENGINEERING

Guided By

Prof. R.D. Palhade

DEPARTMENT OF MECHANICAL ENGINEERINGShri Sant Gajanan Maharaj College of Engineering

Shegaon – 444203 (M.S.)(Affiliated to Amravati University, Recognized by A.I.C.T.E, Accredited by

N.B.A. New Delhi, NAAC, Bangalore & ISO 9001-2000 Certified)2010-11

Website: http://www.ssgmce.org

CERTIFICATEThis is to certify that the following students of the college have

carried the project entitled “COUPLED FIELD FINITE ELEMENT

ANALYSIS OF DISC TYPE INSULATOR ASSEMBLY” Under the guidance

in the Department of Mechanical Engineering during academic year

2010-2011. This work has been done in partial fulfillment of

requirement for completion of Bachelor’s degree in Mechanical

Engineering.

Submitted by

Mr. Swagat S. Giri Mr. Kaustubh S. Nerekar

Mr. Aniket T. Shisode Miss. Prachi S. Giri

Mr. Sagar . Gawande

Guided By

Prof. R.D. Palhade

Dr. V. N. Gohokar Dr. V. N. Gohokar

(Head of Department) (Principal)

DEPARTMENT OF MECHANICAL ENGINNERING

Shri Sant Gajanan Maharaj College Of Engineering

Shegaon – 444203 (M.S.)

(Affiliated to Amravati University, Recognized by A.I.C.T.E, Accredited by N.B.A. New Delhi, NAAC, Bangalore & ISO 9001-2000 Certified)

2010-11

Website: http://www.ssgmce.org

ABSTRACT

A disc insulator assembly is mounted on electric pole to

provide electrical insulation. It consists of a cup, ceramic disc and a forged pin.

As before various researches have done lot of work to develop structural, thermal

and electrical analysis of the insulator. Number of approaches were proposed to

model the insulator and insulator contamination behaviour such as static structural

analysis considering linear behaviour ,thermal and coupled thermo-structural

analysis to account for the stresses due to thermal loading ,transient linear

analysis to consider time dependent electric loading and deformation. The

selected methodology (FEA) involves modelling the disc insulator assembly by

taking exact dimension of an insulator’s components, plotting the keys points, and

creating area one by one in the ANSYS 11.0 working environment. Considering

design guide lines suggested by various researches, behaviour by linear/non linear

material properties, and meshing insulator shapes using axi-ssymmetric element

and by applying the structural, thermal and electrical load for particular boundary

conditions.

From our FE analysis the stresses at various nodes of

different components of an insulator assembly were located. Stress concentration

due to application of structural load was found maximum in the pin and a

moderate stress is transferred to the sealing material (cement). In thermal analysis

temperature distribution was analyzed which shows no temperature change over

the cup but a small change was observed in the disc. Similarly in electrical

analysis voltage distribution over the entire assembly was obtained and found no

voltage around the cup and the cup sealing material. Hence, in future this data can

be extracted to optimize the insulator assembly in various respects such as

compactness, high performance, cost effectiveness and durability.

ACKNOWLEDGEMENT

We are glad to complete the report on the topic coupled field finite

element analysis of disc type insulator which has opened new doors of

knowledge ofr us and has given us good insight.

It is indeed a great pleasure for us to present this project report after having

undergone unforgettable moments of excitement, anxiety, experience and

understanding. This pleasure would not have been without the firm support

extended to us by our guide Prof.R.D.Palhade who encouraged us through his

venture. We like to mention heartily thanks to all the staff members who have

generously helped us in many ways.

Also we are thankful to Prof Bhambele (MECH DEPT.), Mrs. Ashwini

Deshpande (Director, DG Ceramic, Khamgaon) and Mr.A.R.Kamagasahani

(Production Manager, DG Ceramic, Khamgaon) for their valuable guidance and

support throughout the project work.

We also thank to our respected principal Dr.V.N.Gohokar sir ofr their kind

attention toward discipline and punctuality and also all those who have

contributed directly or indirectly in development and evolution of this project

report.

CONTENTS

Abstract

List of figures

List of tables

1. Introduction

1.1 Introduction to insulator

1.2 types of insulators

1.3 Performance of insulators

1.4 In shape for optimum performance

1.5 Material of an insulator

1.6 Different application of insulators

1.7 Detail of disc type insulator assembly

1.8 Objective of present assembly

2. Review Of Literature

3. FEA Of Disc Insulator Assembly

3.1 Finite element analysis

3.2 Axe-symmetric stress analysis

3.3 Structural analysis

3.4 Thermal analysis

3.5 Electrical analysis

3.6 Experiment performed on UTM

4. Result and Discussion

4.1 structural analysis (45 KN load)

4.2 thermal analyses

4.3 electrical analyses

5. Conclusion And Future Scope

REFERENCE

APPENDIX

LIST OF FIGURES

1.1. Pin Type Insulator

1.2. Suspension Type Insulator Fixed In High Transmission Pole

1.3. Strain Type Insulator

1.4. Single Disc Insulator Assembly

1.5. Various Components Of Disc –Insulator Assembly

3.1 Axi-symmetric Model

3.2 Key points Plotted in ANSYS

3.3 Line Joined Through the Key points

3.4 Area Connected

3.5 PLANE223 Element For Couple Mesh

3.6 Meshed Model

3.7 Meshed Model and B.C. For Structural Analyses

3.8 Applied Temperature on Meshed Model

3.9 Applied B.C. And Load Model for Electrical Analysis

4.1 Displacement Vector Model

4.2 1st Principle Stress

4.3 Von Mises Stress

4.4 Vector Plot in Translation

4.5 Nodal Temperature

4.6 Thermal Flux Vector Plot

4.7 Electrical Potential

4.8 Electric Field

4.9 Electric Gradient Vector Plot

LIST OF TABLES

Table No.

1.1. The Characteristics of Various Pin Type Insulators

1.2. Characteristics of Suspension Type Insulator

1.3. Characteristics of Strain Type Insulator

1.4. The Various Mechanical and Thermal Properties Of Ceramics

1.5. Electrical Properties of Ceramics

3.1. The Various Key Points Taken To Model Insulator Assembly On ANSYS

3.2. Structural Properties of Components

3.3. Thermal Properties of Components of the Insulator

3.4. Electrical Properties of the Components

4.1. Maximum Values of Displacement

4.2. Minimum Values of Von Mises Stress

4.3. Maximum Values of Von Mises Stress

4.4 Temperature at Nodes

4.5 Maximum Voltages at a Node

CHAPTER NO. 1

INTRODUCTION TO INSULATOR

1.1 INTRODUCTION TO INSULATOR

High voltage ,insulator are critical components of transmission and

distribution networks and thus the selection of appropriate insulator design for each

insulator design for each application is more important to ensure areliable and secure

supply.unfortunately,the combination of many variable environment parameters

which influence an insulator’s behavior over its lifetime are difficult to artificially

simulate and moreover,to accelerate.The validity of laboratory tests is thus often

questioned.

Insulators are widely used in power system to provide electrical insulation and

mechanical support for high voltage transmission line.to detect and replace faulty

insulators on power transmission lines is of great importance for safe operation of

power system.appropriate shape and dimensioning of insulators in electrical

equipment must provide sufficient mechanical and electrical strength and the required

minimum stress-strain,minimum effect of temperature and required minimum

insuiation resitance during whole lifetime of insulator.standardized dimensions and

shapes rules could support the designers if they give minimum insulation and

classification of very difficult environmental service conditions of electrical

equipments.the main cocern of subsequent insulation design is steady-state voltage

strength,flashover,impulse and mechanical tension/compression etc.adjusting the

insulation strength to the insulation stress provides it.THIS requires knowledge of

mechanisms leading to insulation failure and its dependency on e.g material,shape of

insulator,dimension of an insulator,electrode spacing and voltage etc.The provision of

certain minimum insulation resitance presumes information on long-term behavior of

insulation resitances under the influence of environmental condition.

The insulator have certain insulation level.the insulation level is characterized by the

following:

-normal voltage and highest system voltage.

-one minute power frequency withstands voltage.

-standard lighting impulse withstands level.

-standard switching impulse withstands level.

The impulse withstand level of an insulation is dictated by voltage stresses in the air

near the insulation surface at highly stressed points (conductor or structure).by using

suitable grading rings,the voltage stress `can be reduced substantially and the field

distribution is made more uniform.both lighting and switching impulses have

different kind of stress on insulators and surrounding air.

1.2 Types Of Insulators:

1. Pin/Post Type Insulator

2. Suspension Type Insulator

3. Strain Type Insulator Or Tension Type

1.2.1Pin/Post Type Insulator

As the name suggests th pin type insulator is attached to a steel bolt

or pin which is secured to a cross arm on the transmission pole.two methods generally

used to make this insulator.

1.the provision of taper thread cut on the head of the pin,which crew into the threaded

soft metal thimble cemented into the insulator.

2.the provision of last lead thread on the steel spindle,which screws directly into a

thread formed in the porcelain;on the continent of the pin which has a plain top,is still

sometimes wrapped in hemp and the treaded screwed on.

For operating voltage upto 25000 V with ordinary designs of insulator a piece

construction can be adopted,up to about 45000 V a two pieces,upto 66000 V a three

pieces and so on. Recent progress in design and manufacture has enabled much

thicker section to be adopted,with results for working voltages upto 33000 V a single

piece consruction is possible,and not more than two parts event in largest

sizes.actually ,the tendancy is to use pin type insulator for voltage upto 50000 V

only ,since they become uneconomical for the higher voltages.these is because there

cost increases much more rapidly than the voltage. According to taylor,the ratio of

average initial cost per mile of pin type to suspension type is about four or five ,but

the cost of replacement for suspension insulators usually much lower than pin type

Figure 1.1; pin type insulator

The characteristics of this type are as follows:

Type Usual

working

voltage(KV)

Average

puncture

Voltage(KV)

Height(in) Maximum

Diameter

(in.)

Seepage

Distance

(in.)

Net weight of

porcelain(lb)

11004 3.3 8.53

58

558

514

1 3

16

5063 6.6 1204

14

4 1

166

34

1 34

5065 11.0 1406

58

5 34

11 34

3 1516

11253 33.0 250 910

34

2923

58

Table 1.1:the characteristics of various pin-type insulators

The significance of these figures will appreciated from following notes.there should

be sufficient thickness of porcelain between the line conductor and the insulator

pin(or other metal work) to give a factor of safety upto 10 against puncture,but

insulator should be designed so that it will spark over before it will puncture.the ratio

of spark over voltage to the working voltage is called the safety factor,and for pin type

insulator this factor is much higher for low voltage than it is for high.the present

tendancycy is to use pin type insulator for low voltage only,say upto 11 KV,for which

the factor of safety are 8.3 and 5.0 wet.

The insulator and its pin,or other support,should sufficiently strong mechanically to

withstand the resultant force due to the combined effects of wind pressure and weight

of span(and ice land,if any).at terminal poles there is,in addition,the almost horizontal

pull due to tension of the conductor.this,in particular cause such great Bending

moment at bottom of the pin,with pin type insulators,these being transmitted to the

cross arm,that for a line insulated with pin type insulators,it is desirable to use some

type of strain insulator at all termainal or dead ending poles in connection with

mechanical strength,it is to be noted that insulator is stronger than t he pin.in fact,the

pin should be designed as cantilever and the elastic limit of steel should be just

reached at the load for which pin is designed.

1.2.2. suspension type:

High voltage lines are insulated by means of suspension insulators in which,as their

name indicates,line conductor suspended below the point of support by means of the

insulator or insulators.

seven important advandages of this type are:

Each insulator is designed for low working voltage of 11KV and insulator for

any required line voltage can be obtained by using a ‘string’ of suitable

number of an insulators.

In the event of failure of insulator,one unit of whole string has to be replaced.

The mechanical stresses are reduced,since the line is suspended flexibly;which

pin type insulators,rigid nature of attachment results in fatigue and ultimate

brittleness of the wire,due to the alternating nature of the stresses.also,since

the string is free to swing,there is an equalization of the tension in conductor

of successive spans.

In the event of an increase in operating voltage of the line,this can be met by

adding the requisite number of units of each string,instead of replacing all

insulators,as would be necessary with pin type.

The Hewlett insulators mostly used in our country and it has ten inch disc,each

disc having two curved channels which lies in the planes at right angle to

another one.lead covered steel U links are threaded through this tunnels,are

fastened to the similar links on adjacent upper and lower units.thus no

cementing is required and design is very simple.this ten inch pattern has been

found very suitable for the lines upto 33 KV,where mechanical loading has to

be considered.since ultimate mechanical strength is decided by steel links and

not by porcelain,this pattern is very strong and has peculiar advantage that the

breaking of porcelain disc will not allow the line to fall,in fact in interrupt the

service,if string of several units is used.

Its disadvantage is that construction is of necessary associated with high

electrostatic stresses in the porcelain immediately between the links,so that the

liability to puncture is greater than with other types.

The helwett insulator is used as a strain insulator particularly on pin type

insulator lines upto 33 KV.it is supplied in various disc diameters from 6

inches to 10 inches and for mechanical working loads from 2000 to 8000 lbs.

Type Spark over voltage,

dry(KV)

Spark over voltage,

Wet(KV)

10 inch disc 75 48

6 inch disc 55 27

Table 1.2:characteristics of suspension type insulator

An insulator set complete with fitting to carry a line conductor at lower ends.for this

disc type geometry of insulators is used.

Figure 1.2: Suspension type insulator fixed in high voltage transmission pole.

Strain type or tension type:-

These insulators are used to take tension of the conductor at

line terminals and at points where line is dead ended,as for example some road

crossing,junction of overhead lines with cables, river crossing, at angle tower where

there is change in direction of the line and so on.

For light low voltage lines upto 11KV-shackle type insulator is necessary.

For high voltage lines-suspension type string insulators are used.

It will realized that when strain disc type in vertical instead

of horizontal plain is used, their may some differences to spark over voltages are

shown.

Fig 1.3:Strain type insulators

Characteristics of strain type insulator are as follows:

No in series S.O.V.,dry

(KV)

String effic.

Dry(%)

S.O.V.,wet

(KV)

String effic.

Wet (%)

1 75 100 48 100

2 140 93.4 90 92

3 195 86.7 128 89

4 245 81.8 166 86.5

5 295 78.8 205 85.5

6 345 76.7 245 85.1

7 395 75.4 280 83.4

8 445 74.2 320 83.4

9 190 72.8 355 82.2

10 535 71.4 385 80.3

Where S.O.V=spark over voltage

Table 1.2: Characteristics of strain type insulator

When string efficiency is small,the top units are perfoming very little work

and adding further units has very little effect on the voltage across the unit adjacent to

the line conductor.for 100 KV,string efficiency is large so large number of units per

string will be required. In every case,voltage is on the bottom unit. Good result have

been obtained by using standard insulators for most of the string and larger unit

adjacent to the line , and possibly above.also,with comparatively light lines,it is

possible to use smaller Hewlett units for most of the strings and two or three standard

10 inch units at the bottom.in this way,the total no. of units required and then cost of

string get reduced,but there is still operating disadvantages that stock of different

sized insulator must be carried away.alternately,the capacitance of bottom units can

be increased by fitting metal caps or even by painting a portion of top surface with

conducting paint.in practice the method of capacitance grading is onlyu suitable for

very high lines,say 200 KV or more.

The voltage distribution is controlled in this (static shielding) method

by employment of grading or guarding ring,which usually takes the form of large

metal wing surrounding the bottom unit and connected to the metal work at the

bottom of this unit and therefore to the line.this ring,or shield,as the effect of

increasing the capacitance between the metal work and the line.

With this method,it is impossible to obtain in practice an equal distribution of

voltage,but considerable improvement are possible nevertheless.for example,test on

certain 14 unit string gave 18.3 % of the total voltage on the bottom unit on shielded

and 11.8 %,when shielded.

Potential distribution over a string of suspension insulators

The following results of an actual test on 10 inch suspension insulators show

how the string efficiency depends up on the no. of units in the string, and also on the

condition (whether dry or wet) [S.O.V =spark-overvoltage]

No. in series. S.O.V., dry

(KV)

String Effic.

Dry. (Percent.)

S.O.V., wet

(KV)

String Effic.

wet. (Percent.)

1 75 100 48 100

2 140 93.4 90 92

3 195 86.7 128 89

4 245 81.8 166 86.5

5 295 78.8 205 85.5

6 345 76.7 245 85.1

7 395 75.4 280 83.4

8 445 74.2 320 83.4

9 190 72.8 355 82.2

10 535 71.4 385 80.3

Table: 1.3: Characteristics of strain type insulator

When [the string efficiency] is small, the top units are performing very little

work, and adding further units has very little effect on the voltage across the unit

adjacent to the line conductor. For high voltages, say over 100,000volts, it is thus

imperative that [the string efficiency] shall be large; otherwise, and an impossibly

large number of units per string will be required. In every case, the voltage is on the

bottom unit.

Good results have been obtained by using standard insulators for most of the

string, and larger units for that adjacent to the line, and possibly above. Also, with

comparatively light lines, it is possible to use the smaller Hewlett units for most of the

strings, and two or three standard 10 inc units at the bottom. In this way, the total no

of units required, and therefore the cost of the string can be reduced, but there is still

the operating disadvantage that stock of different sized insulator must be carried.

Alternately the capacitance of the bottom units can be increased by fitting metal caps,

or even by painting a portion of the top surface with a conducting paint. In practice

the method of capacitance grading is only suitable for very high lines, say 200,000

volts or over.

The voltage distribution is controlled in this (static shielding) method by the

employment of grading or guarding ring, which usually takes the form of a large

metal wing surrounding the bottom unit and connected to the metal work at the

bottom of this unit, and therefore to the line. This ring, or shield, has the effect of

increasing the capacitance between the metal work and the line.

With this method, it is impossible to obtain in practice an equal distribution of

voltage, but considerable improvements are possible nevertheless. For example, test

on certain 14 unit string gave 18.3% of the total voltage on the bottom unit on

shielded, and 11.8%, when shielded.

Incidentally, the grading shield serves the purpose of an arcing shield when

used in conjunction with an arcing horn fixed at the top end of the string. In the event

of a power arc following a flash over due to some type of over voltage, the arc will

usually take the path between the horn and the shield, and stay clear of the insulator

string.

1.3. Performance of an insulator:

Furthermore,the performance of insulator in power transmission system is

affected by their electric materials and mechanical properties performance.both

electrical and mechanical are needed to decide which insulators are suitable to apply

to such environment.

Due to there wide role in power transmission and distribution, insulator are

subject to electrical, mechanical and environment stress. Insulators used for safely

equipment purposes are mostly installed indoors. They are subject to mainly electrical

stress more so than mechanical or environmental stress. Line insulators are mostly

installed outdoors and are subjected to mechanical stress due to the conductor weight,

sag, tension and wind.

The unavoidable stress for the outdoor insulator is environmental stress: a high

ambient temperature and a wide range of surface pollution. Environmental effects can

reduce insulation properties of insulators, in particular the polymeric insulator. High

temperatures increase the electrical conductivity, and U.V. sunlight causes a certain

change in chemical bonds of the polymer because of the cross-linking reaction

Moisture will obviously decrease the surface insulation resistance. His condition

exacerbated by the presence of surface contamination due to pollution. Environmental

effects on the polymer insulator provide a substantial area for researchers to

investigate. The rate at which new polymer material have been used has outstripped

the work been done on aging rates of such material. In costal environment and

tropical environment salt is the most common contaminant. Salt will act as an

electrolyte under humid conditions. Electrical conduction on the surface layer can

cause discharges to occur on the surface and cause surface degradation. This

condition weakens the surface insulation significantly and may lead to

breakdown/failure.

Insulators can be defective prior to their insulation due to poor quality control

and mishandling. It is clear that insulator defect problems require the power

companies to perform monitoring on insulators before and during service. Monitoring

for defects is important to avoid unexpected failure that can effect a company’s

reputations.

This chapter discusses the type and designs of insulators on the market, following

by a discussion of their properties. Defects that can occur on insulators prior to

application and during service are described here followed by methods used to detect

the defective insulator.

1.1. In shape for optimum performance

The exterior appearance of high voltage insulator depends on combination of

various factors determining its specific shape. Designing of an insulator for optimum

performance require exact knowledge and description of all application needs.

Mechanical requirements:

The mechanical forces such as bending moment, compression, tension etc

acting on the insulator and its connecting systems must be accurately specified.

Electric Characteristics:

Data such as lighting impulse flash over voltage, switching impulse flashover

voltage and power frequency flash over voltage define the electrical strength and

insulator design.

Creepage Distance Requirement

Creepage distances are defined in accordance with IEC 60815 with costumer

requirements

Application standard and testing codes:

International standard codes and testing specifications are observed in manufacture of

the product.

Costumer Specification and installation requirements

Special requirements (connecting dimensions, diameter etc) are considered during

design.

Environment conditions

Environmental conditions at the installation site determine the design and number of

insulator sheds.

Ceramics

Ceramics insulators are used when electrical insulation is necessary in high heat

applications. This makes them useful for supporting electrical heating elements in

ovens, heaters and furnaces.

Ceramics holds their shape and size under pressure. This is important in switching

application where the ceramic is used to open and close electrical contacts in a

thermostat or pressure switch.

Ceramic parts are very abrasion resistant and offer long life in application where other

materials would wear quickly.

1.1.1. Properties of Ceramic Insulators:

Ceramics are made of an aggregate consisting of particles of different sizes, crystals,

pores. The properties of ceramics depend upon those factors and the manufacturing

process. Particle size determines the mechanical properties of ceramic insulators.

Small particle size give better mechanical strength, but it extends the formation times

of the aggregate from a slurry to semisolid cake, which is not efficient and economic.

During the firing cycle, raw ceramics will shrink due to chemical dehydration and

become denser. Thermal mismatch between the external glaze and body material can

cause internal micro-cracks that reduce mechanical and electrical performance. Silica

in crystalline forms and alumina are usually used to increase glaze mismatch in order

to strengthen the microscopic surface. It can be seen that ceramic manufacture is a

complex process.

1.4.2 Mechanical properties of ceramics:

Ceramics are brittle materials, and therefore very low tensile strength

compared to toughened glass. The details of their tensile strength shown in table 1.3.

alumina filler gives better tensile strength to ceramics material(50-70MPa) then silica

filler (21-42MPa). Glazing also increases the tensile strength of both silica and

alumina field ceramics.

Property Unit Siliceous ceramics Aluminous ceramics Toughened

glass

Unglazed Glazed Unglazed Glazed

Strength MPa

Flexural 42-92 56-120 100-140 120-170 200-250

Tensile 21-42 28-56 50-70 60-80 100-120

Compressive 280-450 360-690 400-600 500-700 700

`Density Gm/cm3

Bulk 2.26-2.42 2.60-3.25 2.30-2.60

No pores 2.42-2.50 2.78-3.47

Fracture

Impact

energy

J 2.30-3.0 2.5-4.0 5.0-6.0

Modulus Gpa 55-80 80-120 60-70

Expansibility x

10^6/K

3.5-5.5 4.6-6.0 8.0-9.5

Thermal

conductivity

W/mK 1.0-2.5 2.0-25.0 0.5-0.9

Table 1.4: The various mechanical and thermal properties of ceramics

1.2. Material of an Insulator:

Material used for outdoor insulator applications depend on many considerations.

There are three main materials that have been used:

Ceramic, glass and composite

Their use and design are determined by their mechanical and electrical

properties and the load or stress that they have to encounter in their application in

addition to weather resistance and vandalism. An ideal design of outdoor insulator

should increase the weather resistance of the material. It has to be able to reduce

pollution accumulation and water condensation on the surface that could increase

surface conductivity. An outdoor insulator should design to resist vandalism.

In designing an outdoor insulator consideration should also be given to

mechanical strength because an insulator also has roll in construction support and load

bearing in addition to electrical insulation role which require high electric strength.

Moreover, resistance to weather and vandals depend on the mechanical and electrical

properties of the material.

1.2.1. Electrical properties of ceramics:

The important electrical properties of ceramics for insulators are relative

permittivity, loss tangent and electrical puncture strength and volume resistivity as

shown in table-----. The electrical puncture stress of the ceramic insulator is less than

20KV/mm. actually, for ordinary ceramic it is 80KV/mm.

Various electrical properties are shown in the following table no. 1.5

Property Unit Siliceous

ceramics

Aluminous

ceramics

Toughened

glass

Permittivity

50-60Hz, 20’C Air=1 5.0-6.5 6.0-7.5 7.3-7.5

1MHz, 20’C Air=1 4.8-5.6 5.0-6.5 7.1-7.5

Loss tangent

50-60Hz, 20’C x10^-3 10.0-25.0 12.0-30.0 15.0-60.0

1MHz, 20’C x10^-3 5.0-12.0 5.0-12.0 5.0-12.0

Puncture strength

50-60Hz, 20’C kV/mm 10.0-20.0 10.0-20.0 >25.0

Impulse(1/5us) kV/mm 40.0-50.0 40.0-50.0 170-220

Volume

resistivity(20’C)

Ohm.cm 10^13 10^12 10^12

Table 1.5: Electrical properties of ceramics

1.6. Different application of Insulators:

1. Pin-type insulators are used for low and medium voltage distribution line.

Usually they are used on overhead lines with not more than 70kV.

2. Strain insulators are used in guys and for dead ending low voltage line.

3. Suspension insulators are used for dead ending lines of any voltage. It is also

used for tangent and angle construction for practically all voltage line.

1.7 Detail of disc-type insulator assembly

Figure 1.4: a single disc insulator assembly

Disc-type insulators are used world wide used in line transmission, either as in

suspension or in strain. Design and manufacturing of disc-type insulator assembly are

being improved in order to meet the requirements of the modern power transmission

and distribution system.

However, there is some limitation on their shed design to satisfy the surface

electrical leakage distance needed for higher voltage transmission. Furthermore, due

to their weight, it is inconvenient to use ceramics insulator in system above 100kV, as

they will become very long and heavy and thus may be damaged.

The cement that used to attach the ceramic insulator shed to the metal cap and

pin in believed to cause electrical puncture on the ceramics insulator in some cases.

Ceramic is brittle, material, and crack and break are common problem. However, they

are not easily shattered.

The basic components of disc insulators assembly are cup, the sealing

material, the ceramics disc, and the forged pin. The basic components of the ceramic

disc are clay, fine sand quartz and feldspar, alumina and cristobalite are usually added

as filler. Glazing is used to smooth the insulator surface, to improve hydrobhobicity,

and also to increase the mechanical strength.

The cap and the pin ceramic insulator were first applied as a suspension

insulator in 1990. The design of the cap and pin is shown in figure1.5. They form

string by joining the cup of the insulator to the pin of the adjacent insulator. The cap is

generally made up of cast iron because of its complicated shape and the pin is made

up of forged steel. Pin is the only component with provide tensile strength to the

insulator assembly because of its very high tensile strength.

Conductive glaze is made by adding iron oxide to the glaze mixture when

applied on the top of the pin type insulator as shown in figure1.6.

Figure 1.5: various component of the disc-insulator assembly

1.7. Objectives of present analysis

The coupled field analysis is done by taking the reference of literature review

papers which were internationally published and we are trying to compare the various

results.

The main objectives of the project work are:

To find out the effect of tension/force applied on the insulator assembly

To find the temperature distribution over the insulator assembly and its effect.

To analyze the effect of electrical potential & electrical field distribution over

the insulator assembly.

1.8. Need of present analysis

To analyze weak area such as maximum stress area of an insulator assembly

To analyze physical deformation of an insulator assembly

To analyze how the temperature distributes within the insulator assembly

To understand the behavior of structural ,electrical ,potential & electrical field

distribution over the insulator assembly.

CHAPTER NO. 2

REVIEW OF LITERATURE

Finite Element Analysis (FEA) is a powerful approximate

numerical technique used to solve engineering problems. FEA has been used

to model various electrical systems and equipments by many researchers.

Two-dimensional as well as three-dimensional models have been mainly used

to study the mechanics of these electrical systems and equipments. Many

researchers have used FEA analysis for analysis of insulators and insulations

in electrical systems, but still there is a lot of scope to investigate proper shape

of insulator for higher performance. Following literature is reviewed to take

guidelines for formulating problem and simulating the problem using Finite

Element Method (FEM) and related areas.

Osamu Fujii, Yukio Mizuno and Katsuhiko Naito[1], The paper discusses a

method to investigate temperature rise of transmission line insulators when

the current carried by the line conductor is high, a series of laboratory

experiments were carried out by flowing current in aluminum conductor steel

reinforced by using current transformers. However, the current carrying

capacity of a conductor is principally militated by its thermal limits. Namely,

sag, loss in tensile strength of conductor, the degradation at the conductor

joints and/or compression clamps, etc. are all thermal limiting factors. The

authors reported the tolerable sag and loss in tensile strength for the existing

aluminum conductor steel reinforced (ACSR) by simulation based on

probabilistic approach using actually recorded climatic data when the current

capacity of the conductor is increased.

However, excess heating of insulators is anticipated due to higher conductor

current, which may reduce electrical and mechanical characteristics of the

insulators. This paper reports results of theoretical and experimental

approaches to this subject. It should be noted that this paper could also be

informative for the maintenance work of power utility companies facing

unexpected high current in case of fault, etc.

S. M. Gubanski[2], The present research on outdoor insulation, aiming to

optimize insulator performance, mainly addresses four broad issues. The first

one concentrates on material and processing technology to obtain knowledge

needed for the development of low surface-tension polymeric materials with

high long-term chemical and physical stability. Possibilities provided by the

use of materials showing even better hydrophobic stability than SIR should be

investigated. One may name here applications of fluorosilicones or specially

patterned SIR surfaces. In the latter case, super-hydrophobic and self-cleaning

properties could be obtained, similarly as happens in nature.

The second objective of outdoor insulation research activities is to concentrate

on a better understanding of the behavior of electrical discharges and their

interactions with insulator surfaces. Changes in the hydrophobic property,

erosion, and tracking, as well as flashover are studied. Although some degree

of understanding has been achieved, there is a need for continuing

investigations of aging mechanisms operating under natural conditions to

establish better protection of insulator housings.

The third area is new measurement techniques and remote sensing systems,

which are being developed for the surveillance and diagnostics of insulators.

Their usefulness should be “calibrated” in a large number of tests. Also,

measurements of surface LC provided useful information. The fourth area, not

discussed here, deals with problems related to the development of material and

insulator testing methods for the prediction of lifetime and for the monitoring

of service performance. New methods and modifications to the existing

accelerated aging tests are being introduced to reduce the testing time and to

better simulate natural field conditions.

R. Boudissa, S. Djafri, A. Haddad, R. Belaicha and R. Bearsch[3], despite

the extensive investigations carried out on the pollution performance of

outdoor insulators, the flashover characteristic and its interaction with

insulator shape is still not very well understood. In this paper, we present

findings of experiments, which allow quantifying the effects of insulator

geometry on the flashover voltage. Two main parameters were considered: the

flashover current (maximum magnitude of leakage current just before

flashover) and the flashover voltage. Known difficulties related to accurate

measurement of these parameters which are due to parallel partial arcs on

some insulators, have been quantified using control insulators and simple

modeling approaches. Furthermore, the effect of insulator shape on arc length

has been quantified using non-uniform pollution techniques.

The pollution performance investigations conducted in this work have shown

that the flashover of insulators is affected by various parameters acting

simultaneously. Conventional methods of polluted insulator characterization

such as ESDD surface conductivity do not account for the properties of the

pollution layer at the instant of flashover current measurements. Here, it is

shown that an accurate estimate of the number of arcs on a particular insulator

can be obtained if its geometry is known although this is not sufficient to

determine the exact magnitude of the flashover current. Insulators with thin

cores compared with their shed diameters have only one single arc. For

insulators that have multiple parallel pre-flashover arcs, a pre flashover current

magnitude much higher than that would lead to flashover would be measured,

which leads to an over estimate of the flashover current. This error was

avoided using a narrow band of pollution along the insulator surface. A

comparison with a control insulator having a small core diameter but no sheds

allowed the determination of the portion of the creepage path used during the

flashover of insulators with sheds. During the flashover, and when the ratio of

the shed overhang to the shed spacing is less than 0.9, the creepage path of the

insulator is fully used. Non-uniform pollution of the insulator surface leads to

lower flashover voltage; the higher the non-uniformity the lower the voltage.

This voltage reduction is explained by a shortening of the flashover arc length.

Klaus Stimper[4], in his research work studied, appropriate dimensioning of

insulators in electrical equipment must provide sufficient electrical strength

and the required minimum insulation resistance during the whole lifetime.

Standardized dimensioning rules could support the designers if they give

minimum insulation distances for a given failure risk. This requires at first a

classification of the very different environmental service conditions of

electrical equipment. The main concern of the subsequent insulation design is

the steady-state voltage strength. Adjusting the insulation strength to the

insulation stress provides it. This requires knowledge of the mechanisms

leading to insulation failure and its dependency on e.g. material, electrode

spacing and voltage. The provision of a certain minimum insulation resistance

presumes information on the long-term behavior of insulation resistances

under the influence of environmental conditions.

The purpose of insulator coordination is the long-term adjustment of insulation

strength to stresses and the provision of an appropriate minimum insulation

resistance. The steady-state voltage causes thermal stresses, mainly by micro

arcing, which depends on spacing, pollution and voltage. The material-

dependent tracking resistance determines the insulator strength.

M. J. Abdullah and D. K. Das-Gupta [5], in this paper reported the details

about ceramic and polymer composite and their properties. Three types of

ceramic/polymer composites were prepared and their electrical, dielectric and

pyroelectric properties were analyzed. The composite PZT5/VDF-TrFE shows

a significantly higher pyroelectric figure of merit than that of PZT. The

dielectric loss of the ceramic/polymer composites as observed to be dominated

by those of the polymer, whereas the ceramic phase may have a significant

contribution on the steady-state electrical conduction and low-frequency

dielectric loss at high temperatures.

Richard L. Goldberg, Michael J. Jurgens, David M. Mills, Craig S.

Henriquez, David Vaughan and Stephen W. Smith[6], this paper addresses

and presented some important finding of the modeling of piezoelectric

multilayer ceramics using finite element analysis. Piezoelectric multilayer

ceramics can lower the electrical impedance and increase the SNR of 2-D

arrays. However, because of the complex 3-D structure of multilayer ceramic

transducers, conventional 1-D models produce inaccurate results when

compared directly to experimental measurements. The authors have

demonstrated that 3-D finite element analysis can accurately predict

transducer performance. We modeled single layer and multilayer PZT

transducers using 3-D FEA. The model produced several types of output:

electrical impedance, transmit output pressure, and 3-D animations of

transducer vibration. Simulated impedance plots were obtained for 2-D and

1.5-D array elements. Finite element analysis correctly predicted the

frequency of all vibration modes as well as the impedance magnitude and

phase. The KLM model, on the other hand, only simulates vibration in the

thickness mode, and the results were inaccurate when compared directly to

measurements. Results were also obtained for transmit output pressure of 1.5-

D array elements. The shape and amplitude of the pressure vs. time plots and

their spectra were accurate for FEA simulations compared to measurements.

Finally, the simulated 3-D animations of transducer vibration provided

valuable insight into the vibration modes of the multilayer ceramic.

These results show that, in the future, finite element analysis can be a valuable

tool to design multilayer ceramic transducers for maximum signal-to-noise

ratio.

He Wei, Yang Fan, Wang Jingang, Yang Hao, Chen Minyou and Yao

Degui[7], in this paper the work focused on finding an effective and

convenient way to detect insulator defects. When there are defective insulators

in an insulator string, the voltage distribution along the string and the electric

field in the vicinity of the string will change.

Suspension insulators are widely used in power systems to provide electrical

insulation and mechanical support for high-voltage (HV) transmission lines.

To detect and replace the faulty insulators on power transmission lines is of

great importance for the safe operation of the power system. A non touch

electric-field measurement method to detect faulty ceramic insulators is

presented, which involves measuring the electric-field of measuring points in

the vicinity of insulator strings and calculating the potential distribution along

HV outdoor insulator strings. It also suggests a way to process the influence

from the tower. The salient feature of this method is the significantly smaller

number of measuring points and the greater distance between measuring

points and insulator strings. Ceramic suspension insulators of 110-kV voltage

ratings have been modeled under clean and dry surface conditions. Good

agreement is obtained between the present calculations and the actual value,

which demonstrates the practical viability of the technique.

A. A. Arkadan[8], presented a graduate course on finite element analysis for

electromagnetic applications. The purpose of this paper is to present a

graduate course on finite element analysis for electromagnetic applications

which is offered at Marquette University. This course covers the theoretical

background which is essential in learning how to model electromagnetic

devices. In addition, the course stresses the practical aspects for method

implementation, and involves the application of the finite element method to

engineering and design problems.

J. T. Burnham and R. J. Waidelich[9], This paper presents the results of

testing and service experience of ceramic and non-ceramic insulators to

gunshot damage by Florida Power and Light (FPL). These results indicate that

there are significant differences in the electrical and mechanical response of

ceramic and non-ceramic insulators to gunshot damage.

Gunshot testing of transmission ceramic and non-ceramic insulators was

performed and the results were compared to the in service experience of a

large utility. Significant differences in the response of ceramic and non-

ceramic insulators to being gunshot were found. These differences were

reductions in electrical and mechanical properties which were dependant on

whether the insulators are line posts or suspensions, as well as whether they

were ceramics or non-ceramics. A major concern was the finding that non-

ceramic suspension insulations were separated more easily than their ceramic

equivalents.

Kenneth N. Mathes[10], in this research work addresses the characteristics of

simple insulator shapes under heavily contaminated conditions have been

investigated with three major objectives in mind. First, Improved

understanding of the performance of insulators under contaminated conditions.

Second, the development of optimized insulator geometries to operate in

contaminated environments especially at very high voltages. Third, the

development of insulator geometries that will most effectively utilize tracking

anti erosion-resistant plastics.

Flashover voltage, scintillation current, and ac resistance of a number of

simple insulator geometries (rods, disks, and cones) have been measured under

contaminated conditions. Results have been compared with porcelain

suspension insulators. Tests were made in a high-density conducting mist and

correlated with the resistivity of the contaminant solution. With such tests it

seems possible to optimize insulator geometries. Flashover voltage of about

twice that for conventional 6-in-long porcelain suspension insulators has been

demonstrated for small diameter cones on rods. While maintaining the same

clearance distance' for an insulator design, the effectiveness (per unit length of

additional creepage distance) decreases with an increase in creepage distance.

This is especially true in the vertical orientation. An increase in insulator

diameter decreases effectiveness. Small diameter rods perform well.

S. Farag, F. M. Zedan, T. C. Cheng, C.Y. Wu. H. Nour, M. Fazelian, M.

Akbar, K. Al-Soufi[11], the present work laid down the new dc insulator

design particularly used in desert environment. The performance of HV

insulators is directly related to the amount, composition, and distribution of

attached surface contaminants. Suspended contamination particles are brought

to the vicinity of HV insulators by wind. Around an insulator string the

dynamic behavior of contaminants, and hence electrostatic forces,

predominantly affect attachment probability. The effect of the electrostatic

forces is the more dominant under dc stress. This paper presents design

modifications of HV insulator shapes leading to more suitable potential

gradient distribution to achieve: Reduction of electric stress on each insulator

unit by producing a uniform potential distribution along the insulator string,

and reduction and/or redistribution of contamination deposition. The design

philosophy adopted in this paper is based on the theory that by optimizing

each individual component of an insulator, the composite design will be

optimal. Theoretical and experimental set criteria and guidelines for the

optimal component design are discussed taking into consideration electrodes,

skirts and body configuration, leakage path and spacing, as well as dielectric

material.

Ahmad S. Ahmad, P. S. Ghosh, Syed Abdul Kader Aljunid, Hussein

Ahmad [12], in this paper addresses on the modeling of various

meteorological effects on contamination level for suspension type of high

voltage insulators using ANN. The aim this paper is to obtain accurate

information about the degree of contamination, which the high voltage

insulators are exposed to when they are installed in coastal areas. Regression

technique has been used successfully in estimating the level of contamination

on high voltage insulator surfaces in terms of Equivalent Salt Deposit Density

(ESDD). This paper has also used artificial neural network algorithm to model

ESDD as a function of various meteorological parameter. A comparative

analysis has been carried out between the two methods in this work.

T. Misaki, H. Tsuboi, K. Itaka, T. Hara[13], This paper describes an

improved surface charge method for computation of three-dimensional electric

field distribution and its application to optimum insulator design. In this

method, each curved surface on which the charge is distributed is divided into

many curved surface elements instead of planar elements. After computing

numerically the charge distribution, the distributions of both potential and'

electric field are obtained. Because the use of many curved surface elements

provides a good approximation of the insulator contour, the correction of

insulator contour to achieve optimum insulator design can be performed

smoothly.

Ivan A. Cermak and P. Silvester[14], A new numerical method is described

for the solution of electric field problems where the field is not bounded in

space, but extends infinitely far. This method belongs to the class of boundary-

relaxation techniques in which an artificial finite boundary condition is

initially introduced to allow solution and then iteratively removed as the

solution proceeds. The method has been implemented in extensive computer

programs, which produce equipotential plots of the electric field in the

neighborhood of dielectric and conductive bodies possessing rotational

symmetry. Application to the analysis of suspension insulators and related

devices is described, and several field plots exhibited for standard insulator

types. The method permits sufficiently short computation times to allow

detailed investigation of the effects of insulator contamination by conductive

substances, variation of dielectric constant, or other factors.

S.Y.Woon, O.M. Querin and G.P. Steven [15], this paper presents a

structural application of a shape optimization method based on a Genetic

Algorithm (GA). The method produces a sequence of fixed distance step-wise

movements of the boundary nodes of a finite element model to derive optimal

shapes from an arbitrary initial design space. The GA is used to find the

optimal or near-optimal combination of boundary nodes to be moved for a

given step movement. The GA uses both basic and advanced operators. For

illustrative purposes, the method has been applied to structural shape

optimization. The shape-optimization methodology presented allows local

optimization, where only crucial parts of a structure are optimized as well as

global shape optimization which involves finding the optimal shape of the

structure as a whole for a given environment as described by its loading and

freedom conditions. Material can be removed or added to reach the optimal

shape. Two examples of structural shape optimization are included showing

local and global optimization through material removal and addition.

R. Sundararajan and R. S. Gorur[16], Presented in their research paper are

the results and analysis of a study of the effect of insulator shapes on the dc

contamination flashover voltage. A dynamic arc model is used for this

purpose. The salient feature of the model is that it takes into account the

geometry of the insulator at every instant of the arc propagation, and thus

includes the role of geometry in the Contamination flashover process. A

variety of porcelain cap and pin insulator geometries that are widely used in

practice have been evaluated using this model.

R. Sundararajan, N. R. Sadhureddy and R. S. Gorur[17], Presented the

development of a user-friendly, interactive personal computer package for

designing insulators to be used in polluted conditions. This is accomplished by

integrating a dynamic arc model that computes the pollution flashover voltage

within the Microsoft Windows application program. Suspension, station post

and pin type insulators of numerous shapes have been incorporated into the

package. The model is capable of handling ac and dc voltages, in addition to

uniform and non-uniform pollution distributions on the insulator surface.

E. Asenjo S., N. Morales O., and A. Valdenegro E [18], presented a method

to calculate the low frequency complex electric field in polluted insulators is

proposed. The method is based on a quasi-static approximation which permits

the decoupling of Maxwell’s equations. The method is implemented

numerically through the finite element technique by defining a complex

functional.

Conclusions Drawn from Literature Survey:

The various researchers have done lot of work to develop structural,

thermal and coupled thermo-structural, thermo-electric/electrostatics analysis

of the insulation/insulator. Number of approaches are proposed to model the

insulation/insulator and insulator contamination behavior such as static

structural analysis considering linear and non-linear behavior, thermal and

coupled thermo- structural analysis to account for the stresses due to thermal

loading, transient linear and non-linear analysis to consider time dependent

electric loading and deformations. Multiple methodologies are proposed to

model the insulation/insulator and insulator surrounding, such as Boundary-

Relaxation Analysis, Inverse Application of Charge simulation method, ANN

and 3-D surface charge method etc.

The selection of the particular method can be justified by criticality of the

application where the insulators are used and resource availability for analysis.

Based on the surveyed literature the solution methodology is planned. The

selected methodology involves modeling the insulator of different shape by

considering the design guide lines suggested by various researchers, behavior

by linear/non-linear material properties, and modeling insulator shapes using

2-D, 3-D or axis-symmetric element and by would applying the structural,

thermal and electrostatics load for particular boundary conditions.

CHAPTER NO. 3

COUPLE FIELD ANALYSIS OF DISC TYPE

INSULATOR ASSEMBLY

3.1 Finite element analysis

Finite element analysis (FEA) has become common place in recent years, and is

now the basis of a multibillion dollar per year industry. Numerical solutions to even

very complicated stress problems can now be obtained routinely using FEA, and the

method is so important that even introductory treatments of Mechanics of Materials

such as these modules should outline its principal features.

In spite of the great power of FEA, the disadvantages of computer solutions must

be kept in mind when using this and similar methods: they do not necessarily reveal

how the stresses are influenced by important problem variables such as materials

properties and geometrical features, and errors in input data can produce wildly

incorrect results that may be overlooked by the analyst. Perhaps the most important

function of theoretical modeling is that of sharpening the designer's intuition; users of

finite element codes should plan their strategy toward this end, supplementing the

computer simulation with as much closed-form and experimental analysis as possible.

Finite element codes are less complicated than many of the word processing and

spreadsheet packages found on modern microcomputers. Nevertheless, they are

complex enough that most users do not end it effective to program their own code. A

number of prewritten commercial codes are available, representing a broad price

range and compatible with machines from microcomputers to supercomputers1.

However, users with specialized needs should not necessarily shy away from code

development. Most finite element software is written in Fortran, but some newer

codes such as felt are in C or other more modern programming languages.

In practice, a finite element analysis usually consists of three principal steps:

1. Preprocessing: The user constructs a model of the part to be analyzed in

which the geometry is divided into a number of discrete sub regions, or

elements, connected at discrete points called nodes. Certain of these nodes will

have fixed displacements, and others will have prescribed loads. These models

can be extremely time consuming to prepare, and commercial codes vie with

one another to have the most user-friendly graphical preprocessor to assist in

this rather tedious chore. Some of these preprocessors can overlay a mesh on a

preexisting CAD file, so that finite element analysis can be done conveniently

as part of the computerized drafting-and-design process.

2. Analysis: The dataset prepared by the preprocessor is used as input to the

finite element code itself, which constructs and solves a system of linear or

nonlinear algebraic equations.

where u and f are the displacements and externally applied forces at the nodal points.

The formation of the K matrix is dependent on the type of problem being

attacked, and this module will outline the approach for truss and linear elastic stress

analyses. Commercial codes may have very large element libraries, with

elements appropriate to a wide range of problem types. One of FEA's principal

advantages is that many problem types can be addressed with the same code,

merely by specifying the appropriate element types from the library.

3. Post processing: In the earlier days of finite element analysis, the user would

pore through reams of numbers generated by the code, listing displacements

and stresses at discrete positions within the model. It is easy to miss important

trends and hot spots this way, and modern codes use graphical displays to

assist in visualizing the results. Typical postprocessor display overlays colored

contours representing stress levels on the model, showing a full-field picture

similar to that of photo elastic or moiré experimental results. The operation of

a specific code is usually detailed in the documentation accompanying the

software, and vendors of the more expensive codes will often offer workshops

or training sessions as well to help users learn the intricacies of code

operation. One problem users may have even after this training is that the code

tends to be a black box whose inner workings are not understood. In this

module we will outline the principles underlying most current finite element

stress analysis codes, limiting the discussion to linear elastic analysis for now.

Understanding this theory helps dissipate the black-box syndrome, and also

serves to summarize the analytical foundations of solid mechanics.

3.2. Axisymmetric stress analysis

The concept of axisymmetry and its general interpolation functions. Here, we

specialize the axisymmetric concept to problems of elastic stress analysis. To satisfy

the conditions for axisymmetric stress, the problem must be such that

1. The solid body under stress must be a solid of revolution; by convention, the

axis of revolution is the z axis in a cylindrical coordinate system (r,Q z).

2. The loading of the body is symmetric about the z axis.

Figure 3.1 : (a) Cross section of an axisymmetric body. (b) Differential element in an

rz plane. (c) Differential element in r-Q plane illustrating tangential deformation.

Dashed lines represent deformed positions

3.3 Couple field analysis:

A couple-field analysis is a combination of anlyses from different engineering

disciplines that interact to solve a goble engineering problem,hence, we often refer to

copled-field analysis as a multiphysics analysis. When the input of one field analysis

depends on the results from another analysis, the analyses are coupled.

3.4 Geometrical characteristics:

The geometrical charactreestics of a cap & pin type insulator are

used for the suspension of 11 Kv overhead transmission lines, the diameter(d), which

is 256 mm , the height(h) which is 152 mm & the leakage distance (ld) which is 280

mm.

3.5 Modeling for coupled field FE analysis:

A schematic view of a ceramic electrical insulator for coupled field analysis is

illustrated in fig. due to symmetry, the half of the axial section 2D is modeled the

finite element mesh for a coupled field analysis, which consist of 3238 nodes and axi-

symmetric quadrial element is1061 shown in fig.3.6.

3.5.1Creation of model:

a. First we have taken the dimension of the insulator assembly with

the help of vernier caliper, thickness gauge and micrometer.

b. We have modeled the insulator assembly in AUTOCAD 2008 and

various keypoints were taken from it as shown in the table 3.1.

Key pts X Y Key. Pts X Y

1 0 0 42 15 -25

2 24 0 43 14.8 -27.6

3 37.5 -13.7 44 0.0 -25

4 23.8 -13.7 45 0.0 -28

5 37.5 -50.2 46 14 -28

6 44.6 -57.4 47 8 -45.0

7 44.6 -57.4 48 8 -120

8 54.6 -57.9 49 16 -124

9 112.8 -67.4 50 7.9 -130

10 53.5 -248.5 51 16 -126

11 125.3 -75.4 52 7.9 -130

12 101.9 -98 53 8 -120

13 131.6 -94.4 54 0.0 -130

14 106.4 -92,2 55 8 45.6

15 114.9 -92.4 56 24.9 45.6

16 123.4 -92.4 57 31.4 39.2

17 114.3 -85.5 58 23.3 37.5

18 99.3 -85.3 59 35 13.6

19 106.8 -85.4 60 -168.8 -1.9

20 98.6 -93.8 62 47.5 -38.4

21 89.6 -93.3 62 -28 -29

22 94.1 -93.9 63 53.4 -45.4

23 88.6 -82.0 64 44 -54.4

24 72.6 -82.8 65 42 -54.4

25 80.6 -81.6 66 39.7 -6.7

26 71.5 -93.8 67 -89.3 -36.9

27 62.6 -94.6 68 24.0 5.0

28 67.0 -93.9 69 21.7 -14.5

29 61.5 -82.0 70 0 5

30 45.6 -80.7 71 0 19.6

31 53.5 -81.9 72 8 19.6

32 45.1 -83.1 73 16.1 23.6

33 36.5 -81.9 74 8.0 29.7

34 40.9 -82.0 75 16.1 25.6

35 35.4 -72.4 76 8 29.6

36 23.8 -71.4 77 8 19.5

37 29.4 -73.6 78 0 80

38 23.3 -73.5 79 157 80

39 17.4 -72.5 80 157 -145

40 20.4 -72.5 81 0 -145

41 17.4 -27.6

Table 3.1: The keypoints taken to model insulator assembly on Ansys.

keypoints :

The above keypoints were taken in the ansys11.0 work environment.

Figure: 3.2. Keypoints plotted in ANSYS

LINE MODEL:

Line model is created by joining these keyp

Figure: 3.3 Line joined through the keypoints

The lines were joined in two steps firstly all the straight lines were

joined by picking line command between two points. Then in

second step by arc command the various curve which was left

were joined, and in this way a complete loop were formed which

can be checked by selecting loop command.

AREA MODEL:

Figure: 3.4 Area created from line one by one

3.3.2 Selecting Element:

After creating insulator assembly suitable element type is selected for

structural analysis which should give minimum warning while messing and

also it should contain all characteristics features mansion in [4]. For this

PLANE 223 is the best suited element as shown below.

Figure: 3.5 PLANE223 element for couple

mesh

PLANE223 is a higher order 2-D, 8-node element. PLANE223 has

quadratic displacement behavior and is well suited to modeling

irregular meshes (such as those produced by various CAD/CAM

systems).This element is defined by 8 nodes having two degrees of

freedom at each node: translations in the nodal x and y directions. The

element may be used as a plane element (plane stress, plane strain and

generalized plane strain) or as an axisymmetric element. This element

has plasticity, hyper elasticity, creep, stress stiffening, large deflection,

and large strain capabilities.

3.3.3 Meshing:

The insulator assembly was meshed using the element PLANE 223 and

each component was specified by their material properties. The

meshing takes 1061 elements and there is 3 element that violets the

shape. A free type is meshing has been done. Which consist of 3238

nodes.

Figure: 3.6 Meshed model

Warning: Shape testing revealed that 3 of 1061 new or modified element

violate shape warning limits. To review test result please see the output file or

issue CHECK command

3.3.4 Define material properties -

The insulator assembly consist of cap, pin , Disc (Silica

ceramic),bonding material Whose properties are shown in table 3.2.

Defining structural properties of each component

component material Modulas of elasticity(E)*10^6,N/mm

Poisson’s ratio(v)

Density(p)*10^-9 ,kg/mm

cap Malleable cast iron

165 0.230 7300

Bonding material

Cement grade 52

25 0.2 2320

disc Silica ceramic

96.5 0.1 3800

Pin Forged steel

200 0.295 7860

Defining thermal properties of each component.

component material Thermal conductivity(K),Watt/mk

Coefficient of thermal expansion (a)*10^-6

Cap Malleable cast iron

55 12.1

Bonding material Cement grade 52

0.29 10

disc Silica ceramic 2.5 5.0-6.5Pin Forged steel 54 11.7

Defining electrical properties for each component:

component material Resistivity (R),ohm-m permittivity

cap Malleable cast iron 10−7 -

Bonding material Cement grade 52 10x1010 2.0

disc Silica ceramic 10x 1011 5.5

pin Forged steel 72 x106 -

Surrounding Air 1

3..5 Apply Boundary conditions and loding:

3.5.1 structural analysis:

In the structural analysis, the boundary conditions are applied on the

lines 57, 56,55,54,52 and loading conditions are applied on the nodes

38,551,397 in downward direction, having magnitude 45 KN.

Figure: 3.7 Meshed model and B.C. for structural analys

3.5.2 Thermal analysis

Boundry condition and load:-We known temperature developed on pin

73.6’C. so a temperature of 73.6’C were applied on pin and a uniform

environment temperature were taken as 30’C.

Figure 3.8 Applied temperature on meshed model

3.5.3 Electrical Analysis

Boundary conditions and load: A voltage of 11kV is applied on pin of the

insulator assembly and current is applied on node 38 is 635.08A.

Figure: 3.9 Applied B.C. and load model for electrical analysis

3.6 SOLVE:

The structural, thermal, electrical analysis is carried out simultaneously.

As mentioned previously in the structural analysis, the PLANE 223 is used for the

couple field analysis.

The boundary conditions are defined for each analysis as per the standards. The

couple field analysis is carried out and results are obtained in the end for each

analysis.

For structural analysis:

The various results of this analysis should be obtained as shown below.

a. Displacement of nodes: This displacement of nodes in X-direction,

Y-direction and the overall displacement is to be finding out.

b. Stresses: The stresses in X-axis, Y-axis and principle stress to be

finding out.

c. Strain: The analysis gave results of strain component in both X-

direction and Y-direction.

For Thermal analysis:

The following results were obtained.

a. Temperature distribution throughout the assembly.

b. Heat flux developed in the assembly.

c. The thermal gradient.

For electrical analysis:

The following results were obtained.

a. Potential distribution:

b. Electric flux density:

c. Electric field:

3.12 Experiment performed on universal testing machine:

Universal testing machine (UTM) is a machine used for testing tensile and

compressive strength of a material or an assembly. It is a conventional way

of testing any component by fixing it in between the two vertical jaws of the

UTM.

3.12.1 Assumptions made for the experimentation

◦ The pin of the insulator is assumed to be uniform throughout its length.

◦ An increasing load is applied rather then sudden load in actual

condition.

◦ Experiment is done till the crack is developed in the assembly rather

deformation of either pin or cup takes place.

3.12.2 Procedure for tensile strength test:

1. Switch on the power and adjust the middle jaw.

2. Insert round headed bar inside the cap, to hold the assembly with the upper

jaw, and a split clamp between the pin to pull the assembly in the other

end.

3. Now open the tensile testing software in the computer.

4. Give the initial input to the software such as diameter of the rod, initial

distance between the two jaws, and the load limitations i.e. upto 400 kN.

5. Give various choices of graphs (stress vs. strain, stress vs. displacement),

we required.

6. As the graph window appears press the testing button.

7. Wait till the component fails.

8. Take the print out of the graphical results obtained.

3.13 Experiment for breakdown voltage.

This experimentation includes two types of tests, dry test and wet test. In dry

test complete dry insulator assembly were placed between the two electrodes,

the electrodes carries a very high voltage from 11kV to 110kV, whereas in wet

test, water is sprayed on the insulator assembly at live condition.

CHAPTER NO. 04

RESULTS AND DISCUSSION

4.1 Structural:

The structural analysis of the ceramic insulator supporting of the electrical

exble weight as a tension of force 45 KN carried out using finite element

coupled field code, in which axi-symmetric structural & interface elament

describe the material behavior loads.

The strength of the electrical insulator ia affected by the shape,size &

position of pin & cap(20). If the pin size is improper,the large tension load is

occurred in the inner part of procelin,which cause the maximum displacement

as 0.0796mm as shown in fig.

Fig4.1: displacement vector model

NODE 39 41 0

VALUE 0.13777E-01 -0.79309E-01 0.0000

Table: 4.1 Maximum values of displacements

at the insulator of proceline-pin very little to insulator. May this tension

accelerates tension fracture in the area of pin-procelain.

Also it shows the maximum 1st principle nodal stress region at intersection of

pin-procelain & at where the bonding material & the sadder geometry changes

of insulator, of value is in between 277 to 370 as shown in fig.

Fig4.2: 1st principle stress

If you study the failure criteria of material as a Von mises stress , of course its

maximum value shown at the top of pin & bonding material also the where the

geometry changes of the insulator. w here the actual load, tension applied that

to be in the magnitude between 533 to 600 N/mm as shown in fig.

Fig4.3: Von mises stress

NODE 492 35 35 5

VALUE -47130 -0.10388E+06 -0.16454E+06 0.000

Table:4.2 Minimum values of von mises stress

NODAL 37 50 50 35

VALUE 37092 18013 3736.3 0.13669E+06

Table:4.3 Maximum values of von mises stress

No such effect shown over the other part of the insulator i.e.

further increase in tension, the Strength of the insulator may decreased. The strength

of insulator is affected by the position & the number of cup jaw, but independent on

the pin geometry. When the direction of the tension in the cup jaw & that of the

tension in the upper of the pin are wincide , may crack is inifiated.

At the corner where there are sudden changes in geometry, not

shown any significant stress concentrated shown as the maximum stress concentration

shown over the pin area near the tension applied region it is also axcepted.

Vector plot:

Fig4.4:Vector plot in translation

4.2 Thermal analysis :

In order to investigate temperature rise of transmission line insulator when the current

carried by the line conductor is high. It is high essential to know the temperature

distribution over the insulator assembly & its effects over the various parts of

insulator assembly.however, the current carrying capacity of a conductor is

principally initiated by its thermal limits .Normally sag, loss in tensile strength og

conductors ,the rotation at the conductor joints &/or compression clamps etc are all

thermal limiting factors.

However ,heating of insulator is anticipated due to higher conductor current which

may reduce electrical & mechanical characteristic of the insulator.

Fig shows the temp distribution at each position at thermal equilibrium ( current -

680.03 amp ,ambient temp 50c)

Fig 4.5: Nodal temperature

Node 34

VALUE 73.6

Table:4.4 temperature at node

In this design of suspension disk insulator ,Portland cement is used in order to

fill up the space between porcelain & metal hardware where the cement acts as a

compression-resistant agent.Thus the compression strength of cement at an elevated

temp is of interest in the present study.

In the present analysis ,the finite element coupled field analysis is done by

taking the input temp 73.6 c over the pin surface area (1). By considering the temp

changes by solar radiation & wi is negligible.A past study indites that the hightest

temp of an insulator is about 50 c in most cases when being directely exposed to the

sun ( 42), further the temp shows over the other part of the insulator gradually

decreasing order as shown in Fig. It could be safely said thet the high temp of the

conductor is not serious to the performance of insulator.here it is showing that the

earlier experiment result (1) matches with the present coupled field analysis 92 to

95%.

Vector plot:

:

Fig4.6: thermal flux vector plot

4.3 ELECTRICAL ANALYSIS:

In the present work the applicaton of separate electrical analysis & coupled-field

electrical FE analysis for the modeling of pin, disk, cap insulator is done.

The disk insulator assembly has been simulated in ansys-11. In order to design the

model of the insulator assembly in the 2-dimenssional program. The axi-symmetry of

the problem is exptoied in the both cases as a separate FE electrical analysis &

coupled field FE electrical analysis

Fig4.7: Electrical potential

NODE 34

VALUE 11000

Table: 4.5Maximum voltage at node

Illustrare the electricl potential & electric field, respectively inside & arrouvd the

pin & porcelain , wich are nearer the transmission line & therefore are more highly

stressrd(22).

Fig.4.8: Electric field

For this glass of problems , the electrostatic solution prements the linitati that

the material are characterial only by their dielectric properties(22), as in present

separate electrical analysis are considered. In order to construct a model that provides

more accurate result,the condacting & dielectric properties of the material must both

be accounted for.the application of alternative formulation that are accounted for the

condacting & dielectric properties of the material in this 2D dimension coupled field

electrical FE analysis is considered & 3-D simulation is a point for futher research.

Aal though to study the behavior of an insulator, which is---- used , & to vering the

surface pollution infance on its dielectric brhaviour(23). The electric field & voltage

distribution are highly affected by the pullation of an electric insulator by

dust,ice,moisture & fog etc. The knowledge of the electric field is more usefull when

it refers to polluted insulator because under operation codition a polluted layer on HV

insulator is very frequent,especially in industrial & castal region, but in this present

research work,this pullation effect is not consider in the both cases.

The coupled field FE analysis of high voltage pin-disk insulator has been

made by using 2-D axi-symmetric element method. According to results which have

been obtained from ansys-11 software,it has been shown that electrical potential &

electric field strength have increased near the pin & the bonding material cement &

negligible near to cap of the insulator & very little transfer to insulator as shown in

fig..

As in reaserch work the analysis of insulator ,by using boundary element method,

ELECTRO software has been shown that potential & electric field-strength have

incressrd in pin & cap of the insulator(34,35).

Vector plot:

Fig 4.9: Electric gradient vector plot

CHAPTER NO. 05

CONCLUSION AND FUTURE SCOPE

1. CONCLUSION

STRUCTURAL ANALYSIS (MAXIMUM WORKING LOAD IS 45 KN):

Maximum deflection at the point of load=1.179 mm

Maximum stress(Y-axis)at the contact of pin and cement

material=26660.7N/mm

Maximum Von mises stress on disc=

Maximum Von mises stress at the contact of pin and cement

material=118628N/mm

THERMAL ANALYSIS – The applied 73.6 0C temp at the pin of the insulator

doesn’t reach to the outer surface its steady at atmospheric temp of 300 C

ELECTRICAL ANALYSIS- No current leakage to the insulator at 11KV.

2. FUTURE SCOPE: -

Optimized geometry of the insulator with all designing parameter.

Optimized the overall performance of the insulator.

Better understanding of behavior of electrical discharges and their interactions

with insulator surfaces.

Effect of temperature rise by the line current of transmission insulator and its

effects will be accordingly identified.

This may provide the knowledge of the mechanisms leading to insulator

failure and its dependency on e.g. material, electrode spacing and voltage; it

may also provide the insulation strength to the insulation stress.

Scope for analysis in CFD.

REFERENCES:

1. Osamu Fujii, Yukio Mizuno and Katsuhiko Naito, “Temperature of Insulator

as Heated by Conductor”, IEEE transactions on power delivery, Vol. 22, No.

1, Page No. 523-526, January 2007.

2. S. M. Gubanski, “Modern Outdoor Insulation-Concerns and Challenges”,

IEEE Electrical Insulation Magazine, Vol. 21, No. 6, Page No. 5-10,

November/December 2005.

3. R. Sundararajan and R. S. Gorur “Effect of Insulator Profiles on dc Flashover

Voltage under Polluted Conditions A Study using a Dynamic Arc Model”,

IEEE "kansactions on Dielectrics and Electrical Insulation Vol. 1 No. 1, Page

No. 124-132, February 1004.

4. Klaus Stimper, “Physical Fundamentals of Insulation Design for Low-voltage

Equipment”, IEEE transactions on Electrical Insulation, Vol. 25, No. 6, Page

No. 1097-1103, December 1990.

5. M. J. Abdullah and D. K. Das-Gupta, “Electrical Properties of Ceramic /

Polymer Composites”, IEEE transactions on Electrical Insulation, Vol. 25, No.

3, Page No. 605-610, June 1990.

6. Richard L. Goldberg, Michael J. Jurgens, David M. Mills, Craig S. Henriquez,

David Vaughan and Stephen W. Smith, “Modeling of Piezoelectric Multilayer

Ceramics Using Finite Element Analysis”, IEEE transactions on Ultrasonics,

Ferroelectrics and Frequency Control , Vol. 44, No. 6, Page No. 1204-1213,

November 1997.

7. He Wei, Yang Fan, Wang Jingang, Yang Hao, Chen Minyou and Yao Degui,

“Inverse Application of Charge Simulation Method in Detecting Faulty

Ceramic Insulators and Processing Influence From Tower”, IEEE transactions

on Magnetics, Vol. 42, No. 4, Page No. 723-726, April 2006.

8. A. A. Arkadan, “A Graduate Course on Finite Element Analysis for

Electromagnetic Applications”, IEEE transactions on Education, Vol. 36 No. 2,

Page No. 233-237, May 1993.

9. J. T. Burnham and R. J. Waidelich, “Gunshot Damage to Ceramic and Non-

ceramic Insulators”, IEEE transactions on Power Delivery, Vol. 12, No. 4,

Page No. 1651-1656, October 1997.

10. Kenneth N. Mathes, “Performance of Simple Insulator Shapers Under Heavily

Contaminated Conditions”, IEEE transactions on Electrical Insulation, Vol. EI-

7, No. 2, Page No. 64-78, June 1972.

11. A. S. Farag, F. M. Zedan, T. C. Cheng, C.Y. Wu. H. Nour, M. Fazelian, M.

Akbar, K. Al-Soufi, “New dc Insulator Design for use in Desert Environment”,

IEEE transactions on Electrical Insulation, Vol. 25, No. 2, Page No. 435-448,

April 1990.

12. Ahmad S. Ahmad, P. S. Ghosh, Syed Abdul Kader Aljunid, Hussein Ahmad,

“Modeling of Various Meteorological Effects on Contamination Level for

Suspension Type of High Voltage Insulators Using ANN”, IEEE transactions on

Power Delivery, Vol. 3, No. 4, Page No. 1097-1103, December 1990.

13. T. Misaki, H. Tsuboi, K. Itaka, T. Hara, “Computation of Three-Dimensional

Electric Field Problems by a Surface Charge Method and Its Application to

Optimum Insulator Design”, IEEE transactions on Apparatus and Systems ,

Vol. PAS-101, No. 3, Page No. 627-634, March 1982.

14. Ivan A. Cermak and P. Silvester, “Boundary-Relaxation Analysis of

Rotationally Symmetric Electric Field Problems”, IEEE transactions on

Apparatus and Systems , Vol. PAS-89, No. 5/6, Page No. 925-932, May/June

1970.

15. R. Boudissa, S. Djafri, A. Haddad, R. Belaicha and R. Bearsch, “Effect of

Insulator Shape on Surface Discharges and Flashover under Polluted

Conditions”, IEEE transactions on Dielectrics and Electrical Insulation, Vol.

12, No. 3, Page No. 429-437, June 2005.

16. R. Sundararajan, N. R. Sadhureddy and R. S. Gorur, “Computer-aided Design

of Porcelain Insulators under Polluted Conditions”, IEEE Transactions on

Dielectrics and Electrical Insulation Vol. 2 No. 1, Page No. 121 to 127,

February 1995.

17. E. Asenjo S., N. Morales O., and A. Valdenegro E, “Solution of Low

Frequency Complex Fields in Polluted Insulators by Means of the Finite

Element Method”, IEEE Transactions on Dielectrics and Electrical Insulafion

Vol. 4 No. 1, Page No. 10 to 26, February1997

18. U. Schümann, F. Barcikowski, M. Schreiber, H. C. Kärner & J. M. Seifert

“FEM Calculation and Measurement of the Electrical Field Distribution of

HVComposite Insulator Arrangements”, 39th CIGRE session, Paris, France,

25-30 August, 2002

19. B. Marungsri, W. Onchantuek, A. Oonsivilai and T. Kulworawanichpong

“Analysis of Electric Field and Potential Distributions along Surface of

Silicone Rubber Insulators under Various Contamination Conditions Using

Finite Element Method”, World Academy of Science, Engineering and

Technology 53, Page No. 1353 to 1365, 2009

20. Y.T. Keum, J.H. Kim and B.Y. Ghoo “Computer aided design of electric

insulator”, Journal of Ceramic Processing Research. Vol. 1, No. 1, pp. 74~79

(2000)

21. D. Mazur and M. Trojnar “3D vibration and stress analysis of insulators”,

International Conference on Renewable Energies and Power Quality

(ICREPQ'08), Santander, 12, 13 and 14 of March, 2008

22. Vassiliki T. Kontargyri, Ioannis F. Gonos, Ioannis A. Stathopulos, and Alex M.

Michaelides “Simulation of the Electric Field on High Voltage Insulators using

the Finite Element Method”, Electromagnetic Field Computation, 12th

Biennial IEEE Conference on, 2006

23. V T Kontargyri, N C Ilia, I F Gonos and I A Stathopulos ” Electric Field and

Voltage Distribution Along Insulators Under Pollution Conditions”,

Proceedings of the 8th WSES World Multi-conference on Circuits, Systems

Communications and Computers» (CSCC 2004), Athens, Greece, (paper 487-

726), July 12 - 15, 2004

24. W. Bretuj, J. Fleszynski, A. Tyman and K. wieczorek “Effect of silicone rubber

insulators’ profiles on their ageing performance in rain conditions”, XVth

International Symposium on High Voltage Engineering, University of

Ljubljana, Elektroinsititut Milan Vidmar, Ljubljana, Slovenia, Page No.1-4,

August 27-31, 2007

25. M.W. Hooker, T.D. Taylor, H.D. Leigh, S.A. Wise, J.D. Buckley, P. Vasquez,

G.M. Buck, and L.P. Hicks, “Effects of process variables on the properties of

yba2c~307ceramics formed by investment casting”, IEEE Transactions On

Applied Superconductivity, Vol. 3, No.1, Page No. 1154-1156, March 1993

26. Guoxiang Xu and P. B. McGndh “Electrical and Thermal Analysis of Polymer

Insulator under Contaminated Surface Conditions”, IEEE Transactions on

Dielectrics and Electrical Insulation Vol. 3 No. 2, Page No. 289-298, April

1996

27. Qiming M. Zhang and Jianzhong Zhao, “Electromechanical Properties of Lead

Zirconate

Titanate Piezoceramics under the Influence of Mechanical Stresses”, ieee

transactions on ultrasonics, ferroelectrics, and frequency control, vol. 46, no. 6,

Page No. 1518-1526, November 1999

28. T.G. Engel, M. Kristiansen, E. O'Hair and J.N. Marx,” Estimating the erosion

and degradation performance of ceramic andpolymeric insulator materials in

high current arc environments”, IEEE Transactions On Magnetics, Vol. 27,

No. 1, Page No. 533-537, January 1991

29. Johan Driesen, Ronnie Belmans and Kay Hameyer, “Finite Element Modeling

of Thermal Contact Resistances and Insulation Layers in Electrical Machines”,

IEEE Transactions on Industry Applications, Vol. 37, Issue-1, Page No. 15-20,

Jan/Feb-2001

30. Farhad Shahnia, A. Mashhadi Kashtiban, K. Roushan Milani and M. Tarafdar

Haque “Insulation Effects and Characteristics of XLPE Covered Overhead

Conductors in Low and Medium Voltage Power Distribution Systems in Iran”,

Conference Record of the 2006 IEEE International Symposium on Electrical

Insulation, Page No. 64-67

31. John A. Rice, Paul E. Fabian and Craig S. Hazelton, “Mechanical and

Electrical Properties

of Wrappable Ceramic Insulation”, IEEE Transactions on Applied

Superconductivity, VOL. 9, NO. 2, Page No. 220-223, JUNE 1999

32. Michael J. Haun, Eugene Furman, Sei Joo Jang, and Leslie E. Cross,

“Modeling of the Electrostrictive, Dielectric, and Piezoelectric Properties of

Ceramic PbTi03”, IEEE Transactions on Ultrasonic, Ferroelectrics, And

Frequency Control, Vol. 36, No.04, Page No. 393-401, 4. July 1989

33. D. S. Kwag, H. G. Cheon, J. H. Choi, H. J. Kim, J. W. Cho, and S. H. Kim,

“Research on the Insulation Design of a 154 kV Class HTS Power Cable and

Termination”, IEEE Transactions On Applied Superconductivity, Vol. 17, No.

2, Page No. 1738-1742, June 2007

34. S.Y.Woon, O.M. Querin and G.P. Steven, “Structural application of a shape

optimization method based ona genetic algorithm”, Struct Multidisc Optim 22,

57–64 @Springer-Verlag 2001, Page No. 57-64

35. Selçuk Yildirim, Sami Ekici and Mustafa Poyraz, “The electric field analysis

of a high voltage

Insulator by using boundary element method”,

36. WL Vosloo and JP Holtzhausen, “The electric field of polluted insulators”,

37. Jamies M. Atkins and Roland L. Gingrich, “High-Density Conducting Mist

Test for Insulator Evaluation”, IEEE Transactions on Electrical Insulation,

Vol. EI-7, No. 2, Page No. 58-63,June 1972

38. U. Schümann, F. Barcikowski, M. Schreiber, H. C. Kärner and J. M. Seifert,

“FEM Calculation and Measurement of the Electrical Field Distribution of HV

Composite Insulator Arrangements”, TU Braunschweig, Schleinitzstraße 23,

D-38106 Braunschweig, Germany

39. M. Kuhl, CeramTec AG and A. Schutz, “Design criteria of composite

Insulators for use in HV outdoor applications”, CIGRE SC 22, Jornada

Tecnica Sobre Aislante Compuesto EN Lineas Electricas, Madrid, 29 de Mayo

de 1997

40. A. Bansal, A. Schubert,b M. V. Balakrishnan & M. Kumosaa “finite element

analysis of substation composite Insulators”, Composites Science and

Technology 55 (1995) 375-3890 1996 Elsevier Science Limited Printed in

Northern Ireland.

41. Weiguo Que and Stephen A. Sebo, “Electric Field and Potential Distributions

along Dry and Clean Non-Ceramic Insulators”, Integrated Engineering

Software - Website Links

42. H. Fukui, K. Naito, T. Irie, and I. Kimoto, “A practical study on application of

semiconducting glaze insulators to transmission lines,” IEEE Trans. Power

App. Syst., vol. PAS-93, no. 5, pp. 1430–1438, Sep./Oct.1974.

43. H. Nishida, S. Yokosuka, M. Matsudo, and T. Katayori, “Structural strength of

ultra high-strength concrete and its mechanical characteristics at high

temperature,” (in Japanese) Trans. Jpn. Concr. Inst., vol. 26, no. 1, pp. 393–

398, 2004

PLANE223 Input Data

The geometry, node locations, and the coordinate system for this element are shown

in Figure 223.1: "PLANE223 Geometry". The element input data includes eight nodes

and structural, thermal, and electrical material properties. The type of units (MKS or

user defined) is specified through the EMUNIT command. EMUNIT also determines

the value of free-space permittivity EPZRO. The EMUNIT defaults are MKS units

and EPZRO = 8.85e-12 Farads/meter.

KEYOPT(1) determines the element DOF set and the corresponding force labels and

reaction solution. KEYOPT(1) is set equal to the sum of the field keys shown in Table

223.1: "PLANE223 Field Keys". For example, KEYOPT(1) is set to 11 for a

structural-thermal analysis (structural field key + thermal field key = 1 + 10). For a

structural-thermal analysis, UX, UY, and TEMP are the DOF labels and force and

heat flow are the reaction solution.

Table 223.1  PLANE223 Field Keys

Field Field Key DOF Label Force Label Reaction Solution

Structural 1 UX, UY FX, FY Force

Thermal 10 TEMP HEAT Heat Flow

Electric Conduction 100 VOLT AMPS Electric Current

A summary of the element input is given in "PLANE223 Input Summary". A general

description of element input is given in Element Input. For axisymmetric applications

see Axisymmetric Elements.

PLANE223 Input Summary

Nodes

I, J, K, L, M, N, O, P

Degrees of Freedom

Set by KEYOPT(1). See Table 223.2: "PLANE223 Coupled-Field Analyses".

Real Constants

None

Material Properties

See Table 223.3: "PLANE223 Material Properties".

Surface Loads

See Table 223.4: "PLANE223 Surface and Body Loads".

Body Loads See Table 223.4: "PLANE223 Surface and Body Loads".

Special Features Large deflectionStress stiffening

KEYOPT(1) Element degrees of freedom. See Table 223.2: "PLANE223 Coupled-Field Analyses".

KEYOPT(2) Structural-thermal coupling method (KEYOPT(1) = 11, 111, or 1011):0 --  Strong (matrix) coupling – produces an unsymmetric matrix. In a linear analysis, a strong coupled response is achieved after one iteration.1 --  Weak (load vector) coupling – produces a symmetric matrix and requires at least two iterations to achieve a coupled response.

KEYOPT(3) Element behavior:0 --  Plane stress1 --  Axisymmetric2 --  Plane strain

KEYOPT(4) Electrostatic force in electroelastic analysis (KEYOPT(1) = 1001):0 --  Applied to every element node.1 --  Applied to the air-structure interface or to element nodes that have constrained structural degrees of freedom.2 --  Not applied.For more information, see Electroelastic Analysis in the Coupled-Field Analysis Guide.