Modeling and Simulation of Porcelain Disc Insulators using Finite Element Method in OPERA Software

International Conference on Magnetics, Machines & Drives (AICERA-2014 iCMMD)

978-1-4799-5202-1/14/$31.00 ©2014 IEEE

Modeling and Simulation of Porcelain Disc Insulators using Finite Element Method in OPERA Software

Dr.M.Padma Lalitha , Member IEEE

Professor & H.O.D, Dept. of EEE

A.I.T.S–RAJAMPETA, A.P, INDIA [email protected],

K.Venkata Pavan Kumar PG student (EPS), Dept. of EEE

A.I.T.S–RAJAMPETA, A.P ,INDIA

[email protected]

Venkatesu Samala Sr.Application Engineer

ICON Design Automation Pvt.Ltd,INDIA

[email protected]

Abstract: The objective of this dissertation is to investigate the potential dispensation and electric stress dispensation of porcelain disc insulator. The Insulator banks used for suspension of overhead power transmission lines constitute most important part of the transmission system. Insulators plays multiple role in power transmission system, they provides mechanical support to conductors and are used to decrease leakage current from live phase to earth. Potential dispensation and Electric stress dispensation throughout insulator bank is greatly uneven. In the present work a prototype of the 132KV insulator string in both 2-Dimension & 3-Dimension was set up using OPERA, a finite element environment for the complete analysis and design of electromagnetic applications. The OPERA ST and Lossy Dielectric are used to return the field values of the electric stress and potential dispensation on the surface of the insulators. The results obtained from both 2-D and 3-D are compared.

Index Terms: Electric stress Dispensation, Finite Element Method,

Opera, Porcelain Insulator, Potential Dispensation

I. INTRODUCTION

The acquaintance of the dispensation of the electric

stress and potential throughout the insulator bank is a key

point for the design of insulators. The number of discs to be

placed depends upon the line voltage of the transmission line.

Each disc with stands for a voltage of 11KV. The Potential

and the Electric stress on the insulator discs near the

conductor exceeds by three to five times than at the other

discs, that can lead to insulator surface breakdown and flash

over may occur. Several experimental and calculation

methods have been developed for the calculation of the

voltage dispensation over an insulator bank and the study of

the fickle capacitances [1]-[3].

Number of experimental and paralleling methods are

developed for the understanding of potential and electrical

dispensation along an insulator bank [4]-[13]. Paralleling

methods give the possibility to study the behavior of

prototypes that are with complex geometry without using

analytical methods or experiments.

FEM is used to compute the Electric stress and

voltage dispensation along insulators with asymmetric

boundary conditions has been proposed by many authors[6]-

[10].

A 2-D prototype for potential and Electric stress

calculating along an composite insulators are presented in [8].

A 2-D prototype was used for paralleling of Electric stress

dispensation on ceramic insulators in [8].

The Electric stress and potential around and inside

the insulator string using 3-D FEM model was simulated in

OPERA [6] & [10].

Numerical knacks had been developed for

manipulating the electric stress and potential in and around

high voltage equipment. BI equations had developed to study

the electric stress and potential of polluted insulator [10].

In this work porcelain disc insulator strings are

modeled in 2-D & 3-D in OPERA. FEM is used to return the

field parameters. In this work a small pollutant layer is also

added on the surface of the insulators. The Electric stress and

potential dispensations along insulators are computed in both

2-D and 3-D and results are compared.

II. FINITE ELEMENT METHOD

The concept of the FEM is “dissociate and

associate’’, to dissociate is for the element to analyze and to

associate is for analysis of the whole prototype. According to

International Conference on Magnetics, Machines & Drives (AICERA-2014 iCMMD) FEM, the process of electric stress dispensation modelling

and calculation are as follows:

1. Discretization is applied to the prototype and then

elements and nodes are propagated. Elements are

coupled jointly by the nodes to form the whole

prototype.

2. Based on the divergent idiosyncrasy of various

materials attached to the prototype, corresponding

parameters of electrical idiosyncrasy will be defined

to each element.

3. Maxwell equations and boundary conditions are

used to connect all elements together according to

their original structure by proper simplifying and

then finite element equations are formed.

4. Regarding to specific feature, exact calculation

method has to be selected to solve the field equations

of unknown nodes. Distinctive result matrix that is

obtained in respect to distinctive method can be

solved by step by step method.

In the present work, the insulator strings are solved using

electrostatic solution.

III. SIMULATION PROCEDURE

OPERA is a package of solvers for 2-D and 3-D

electromagnetic field analysis. It uses the FEM to manipulate

the partial distinctiveial equations that describe the behaviour

of fields. The ST and Lossy Dielectric solver provide field

solution variables that address designs with conducting -

dielectric materials under static and transient conditions and

is applicable for the design of electric insulating components.

Opera manipulates for current flow problem and forwarded

the results as input to electrostatic problem.

The software manipulates the potential by

deciphering the conduction equation.

J = σ.E (1)

The EFI (E) is given by

E = - ∇.V (2)

Now substituting equation (2) in equation (1) and applying

divergence on both sides

∇J = ∇σ∇V = 0 (3)

The divergence of EFD (D) is equal to charge density ρ:

∇. D = ρ (4)

Now from combining equation (2) and equation (4) and

introducing the dielectric permittivity ε (D= εE) arise the

usual Poisson’s equation of the static potential:

∇ ε ∇V = −ρ (5)

The analysis of the model is done using FEM by

dissociating the region of the prototype into linear triangular

elements. The occupancy of the finite element mesh is made

to be concentrated higher at critical regions of the insulator

than in the rest of the area in the model. This gives the user

two advantages such that the complexity decreases and

simulation time is decreased.

IV. PARAMETERS OF INSULATORS

In this work the authors have modeled Porcelain disc

insulators. The physical idiosyncrasy of each insulator disc

are: dia 280mm, height 146mm and the creepage distance is

305mm.

V. SIMULATION RESULTS

In 2-D, the potential is applied to the metal pin at the

top & bottom using boundary conditions. In this model the

author simulated the model for 76.210KV one phase voltage

of the three phase transmission line which is applied at the

bottom & the Metal cap at the top is assigned to zero potential

using boundary condition.

In 3-D, the potential is applied to the long metal rod

which is modeled and connected with last insulator disc with

the help of union operation. The potential of 76.210KV is

applied by picking all the faces of the metal rod. The plate at

the top of the insulator is acted as earth plate which is

assigned as 0V. The outer boundary is also assigned with 0V

International Conference on Magnetics, Machines & Drives (AICERA-2014 iCMMD) A. Porcelain insulator in 2-dimension

The two-dimensional model of porcelain insulator

string is represented in below figure1.

Fig.1: Geometrical model of Porcelain Disc Insulator

Porcelain disc insulator consists of three main parts:

metal (pin & cap), porcelain disc, cement. The relative

permittivities of cement and porcelain are 14 & 8

respectively.

A very thin pollution layer is added to the disc to

operate in any atmospheric condition and highly polluted

areas like near Industries which releases smoke. The

conductivity of pollution layer may extend up to 40µS.

The OPERA-2d ST (electrostatic solver) in addition

with Lossy dielectric solver has been used to manipulate the

potential and electric stress dispensation throughout insulator

discs.

The potential dispensation in and around the

insulator discs is represented in below figure2.

Fig.2: Potential dispensation in and around the insulator discs

The Electric stress dispensation in and around

insulator discs is shown in figure3.

Fig.3: Electric stress dispensation in and around the insulator discs.

Figure 4 gives the voltage dispensation throughout

the creepage path of insulator. Figure 5 gives the Electric

stress through the same path. Perfect agreement had been

acquired from the results.

For understanding dispensation of potential and

electric stress about insulator string four lines are considered

at distinctive locations as represented below.

Note

Line 1: At the centre of the insulator string i.e., R=0 and Z=0

- 1600

Line 2: This is lateral to line 1 and at a distance of R=20.



Potential counters through the creepage path of the

insulator surface are represented in figure 4.


Fig. 4: Potential counters along creepage path of insulator discs

Electric stress counters along leakage path of

insulator discs are represented in figure 5.

Fig 5: Electric stress along creepage path of insulator discs

Figure 6 and Figure 7 illustrates the potential and

electric stress dispensation through the creepage path of

insulator respectively without considering the lossy dielectric

solver. In order to study the dispensation of potential and

electric stress about insulator string four lines are considered

at distinctive locations as represented in Note.

Potential counters through creepage path of the


Fig. 6: Potential counters along creepage path of the insulator discs

Electric stress counters through creepage path of the


Fig 7: Electric stress along creepage path of insulator discs

The 2-D model electrostatic results of potential and

electric stress dispensation are deviated from each other due

to lack of correct representation of conducting material

properties as well as the presence of non-symmetric parts of

the device. For better and accurate results the strings are

modelled in 3-D and simulations has been carried out by with

and without considering lossy dielectric solver.

B. Porcelain Insulator in 3-Dimension

The 3-D prototype of porcelain insulator bank is

represented in below figure8.

Fig.8: Three dimensional model of porcelain disc insulator string.

The OPERA-3d TOSCA (electrostatic solver) in

addition with Lossy dielectric solver has been used in order to

compute the potential and electric stress dispensation

throughout the insulator discs.

The potential dispensation throughout the insulator

discs is as shown in figure 9, by taking a patch.


Fig.9: Potential dispensation in and around the surface of insulator discs

The Electric stress dispensation throughout the

insulator discs is as shown in figure 10, by taking a patch.

Fig.10: Electric stress dispensation in and around the surface of

insulator discs

Figure 11 represents the potential dispensation

through the creepage path of the insulator surface. Figure 12

represents the electric stress the same path. Perfect agreement

had been acquired from the results.

In order to study the dispensation of potential and

electric stress on insulator string four lines are considered at

distinctive locations as represented in Note.

The potential counters through creepage path of the


Fig.11. Potential counters along leakage path of the insulator discs

The Electric stress counters through creepage path of

the insulator discs are shown in figure 12.

Fig.12: Electric stress counters along leakage path of the insulator discs.

Figure 13 and Figure 14 illustrates the potential and

electric stress dispensation over the leakage path of the

insulator respectively without considering the lossy dielectric

solver.

In order to understand the dispensation of potential

and electric stress about insulator string four lines are

considered at distinctive locations as represented in Note.

The potential counters through creepage path of the

insulator discs are shown in figure 13.


Fig.13. Potential counters along creepage path of the insulator discs

The Electric stress counters through creepage path of

the insulator discs are shown in figure 14.

Fig.14: Electric stress counters along creepage path of the insulator discs.

VI. CONCLUSION

In the present work the authors attempt to

understand potential and electric stress dispensation of

porcelain insulator string using FEM. Calculation of potential

and electric stress are useful to indicate sensitive areas of

insulator units those which are prone to breakdown. For this

132 KV insulator strings are modelled in 2-D and 3-D,

simulations were carried out using OPERA. The 3-D

prototype of an insulator bank in addition with a conductor of

transmission line had finely modelled which for the

improvement of simulation accuracy. By observing the plots

a good agreement has been ascertained between the results

obtained from both 2-D and 3-D. The results obtained in 2-D

with lossy dielectric solver are nearly equal to 3-D results

(with and without LD solver). It is conformed from the results

obtained that the most sensitive areas of electric stress are at

the triple junction of the bottom disc of insulator unit. It has

also consummate, by moving away from the string, the

dispensation of potential & electric stress decreases. This

approach can be applied to any type of insulators which gives

accurate results in economic way, which helps the

manufacturers and High Voltage planers to make selection of

right insulator.

ACKNOWLEDGEMENTS

Authors want to acknowledge the department of

A.P.TRANSCO especially to P.Ganesh Reddy - Assistant

Engineer - Rajampeta for providing the technical parameters

of Insulators.

REFERENCES [1] "Investigation on the characteristics of a string of insulator due to

the effect of dirt", by S.M.A. Dhalaan, and M.A. Elhirbawy in Transmission and Dispensation Conference and Exposition,200 IEEE PES, 7-12 September 2003, Vol. 3, pp. 915-920.

[2] "Simulation of voltage distribution calculation methods over a

string of suspension insulators", by S.M.A. Dhalaan, and M.A. Elhirbawy, in Transmission and Dispensation Conference and Exposition, 2003 IEEE PES, 7 -12 September 2003, Vol. 3, pp. 909 – 914.

[3] V. T. Kontargyri, I. F. Gonos, I. A. Stathopulos, A.M.

Michaelidis, "Calculation of the Electric stress on an insulator using the Finite Elements Method", 38th International Universities Power Engineering Conference (UPEC 2003), Thessaloniki, Greece, September 1-3, 2003, pp. 65-68.

[4] "Electric field and voltage distribution along insulators under pollution conditions", by V. T. Kontargyri, , I. A. Stathopulos, I. F. Gonos, N. C. Ilia in 4th Mediterranean IEE Conference and Exhibition on Power Generation, Transmission, Dispensation and Energy Conversion (Med Power 2004), Lemesos, Cyprus, November 15 -17, 2004.

[5] "Calculation of the Electric field on an insulator using the Finite Elements Method", by, I. F. Gonos, I. A. Stathopulos, V. T. Kontargyri , A.M. Michaelides, at 38th International Universities Power Engineering Conference (UPEC 2003), Thessaloniki, Greece, September 1-3, 2003, pp. 65-68.

[6] Measurement and Verification of the Voltage Distribution on

High Voltage Insulators", by V.T. Kontargyri, I.F. Gonos, I.A. Stathopoulos, A.M. Michaelides, 12th Biennial IEEE Conference on Electromagnetic Field Computation, May 1 -3, 2006, pp. 326 – 326.

[7] “Simulation of the Electric field on Composite Insulators using

the Finite Element method” by V.T.KONTARGYRI , I.F.GONOS,N.C.ILIA, I,.A.STATHOPULOS.

[8] “ Simulation of the Electric field Dispensation on Ceramic

Insulator Using Finite Element method”, by Sh.M.Faisal, European Transactions on Electrical Power, Vol 19, No 3, (2009) , pp.526-531.


[9] “Measurement and Simulation of the Electric field of high voltage Suspension Insulators”, by Vassiliki T.Kontargyri , Ioannis F. Gonos and Ioannis A. Statthopulos, in European Transactions on Electrical Power, Vol 19, No 3, (2009) , pp.509-517.

[10] J.L. Rasolonjanahary, L. Krähenbühl, A. Nicolas, “Computation

of Electric stresss and potential on polluted insulators using a boundary element method”, IEEE Transactions on Magnetics, Vol. 28, No. 2, March 1992, pp. 1473-1476.

[11] Vector Fields, “OPERA-2d & 3-d User Guide”, Vector Fields

Limited, England, 1999.

Dr.M.Padma Lalitha obtained graduate

degree in Electrical & Electronics

Engineering from JNTU, Anathapur in the

year 1994. Obtained Masters (PSOC) from

SriVenkateswara.University, Tirupathi in

2002 and awarded doctorate for“Soft

Computing Techniques for optimal DG

placement in Radial Dispensation System “

from Sri Venketeswara.University,. in 2011 and Having 17 years of teaching

experience for graduate and post graduate level. Editorial board member for

Reputed International Journals. Has 50 international journal publications to

her credit and also published two books . Presently working as Professor and

HOD of EEE department in AITS, Rajampet. Areas of interest include radial

dispensation systems, soft computing in power systems, ANN, FACTS ,

Design of Electro Magnetic devices.

K.Venkata Pavan Kumar obtained graduate

degree in Electrical & Electronics Engineering

from JNTU-Ananthapur in the year 2012. He is

currently pursuing his Post Graduation in

Annamacharya Institute of Technology &

Sciences – Rajampeta (Autonomous). He is

presently working as Intern in Icon Design

Automation Pvt. Ltd-Bangalore.His areas of

interest includes Design of Power System applications, Modeling and

controlling of electrical machines, Finite Element Analysis of

electromagnetic devices , Dispensation Systems

Venkatesu Samala obtained graduate

degree in Electrical Electronics

Engineering from JNTU, Hyderabad in

the year 2006. He obtained PG

Diploma in VLSI from Semi-conductor

Laboratory, Chandigarh in 2007. He

has half decade of acquaintance and

experience for supporting the Low

Frequency Electromagnetic applications

involving Design, & Analysis. He has expertise in electromagnetic analysis

of electrical machines using Vector Fields Opera 2D / 3D FEA and analysis

of BLDC and Induction machines. Verification of electromagnetic actuators,

magnet systems and transformers electromagnetic design analysis. Areas of

interest include Finite Element Analysis (FEA), Machine Design & Analysis

and Design of Power System applications.

Modeling and Simulation of Porcelain Disc Insulators using Finite Element Method in OPERA Software

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