A Review of Electric Utility

1
A Review of Electric Utilitys Experiences with
Polymeric Insulators

• Khaled Y. Al-Soufi
• Ibrahim O. Habiballah
• KFUPM, Saudi Arabia
• December, 2004

2
Outline

• Introduction
• International Survey
• Countys service Experience
• Laboratory Test Methods
• Conclusion

3
Introduction

• Gulf Council Countries (GCC) are extended along
  the coast of the Arabian Gulf and through vast
  desert areas
• These areas are affected by severe weather
  conditions which are characterized by high
  temperature, large daily and seasonal temperature
  variations and high humidity levels through the
  summer months

4
Introduction

• The severity and diversity of these weather
  conditions affect the performance of the
  electrical network hardware, such as the
  insulators

5
Introduction

• Various kind of polymers, such as silicone
  rubber, EPDM (Ethylene Propylene Dine Monomer),
  EVA (Ethylene Vinyl acetate Copolymer) and PTFE
  (Poly Tetrafluoro Ethylene) were used for outdoor
  insulation in different applications including
  transmission/ distribution insulators, post type
  insulators and hollow core types for apparatus

6
Introduction

• A serious problem with polymeric insulators,
  however, is their sensitivity to atmospheric and
  electrical stresses in outdoor applications which
  can lead to the aging phenomena of the polymeric
  insulator and may lead to reduction in the useful
  life of the insulators

7
Introduction

• Selection of a polymeric insulator for a given
  site must be based on careful analysis and
  testing
• The main objective of this paper is to present a
  thorough literature review and investigations of
  local and international electric utilitys
  experiences with polymeric insulators

8
Introduction

• The paper will also present the major procedure
  needed to assess the performance of such
  insulators in the GCC area

9
International Survey

• Through the last three decades huge amount of
  data collected about polymeric insulator
  performance and utility service experiences
• CIGRE, EPRI, Japanese manufacturer and research
  centers conducted international surveys about
  utilities service experience with polymeric
  insulators

10
International Survey

• The CIGRE working group dealing with polymeric
  insulators distributed questionnaire in 1987,
  with various questions on experience with
  polymeric insulators to many electricity
  companies all over the world

11
International Survey

• The major outcome regarding the use of polymeric
  insulators To combat vandalism, easy
  transportation and installation,
  anti-contamination capabilities, high
  strength-to-weight ratio and for aesthetic
  appearance

12
International Survey

• CIGRE made another survey in 2000
• This survey indicated the findings of the
  previous Cigre survey and nominated silicone
  rubber material as the most widely used for
  polymeric insulators in Africa, Asia, Australia,
  Canada, Europe, South America and Middle East

13
International Survey

• EPRI of the USA has distributed questionnaire to
  the utilities in the USA in 1989
• The survey indicated that the polymeric post
  insulators were used more frequently at the 115
  kV and 138 kV levels, whereas polymeric
  suspension insulators are most prevalent at 230
  kV

14
International Survey

• Reasons cited by utilities for this early survey
  gave high percentage to combating vandalism, and
  then other reasons follow as experimenting and
  light weight.

15
International Survey

• EPRI made another recent survey Polymer
  Insulator Survey in 2002
• The results of the survey indicated that the
  failure rate for all manufacturers that provided
  sales information was 1 in every 65,500 units
  sold

16
International Survey

• Japan started a Research and Evaluation Program
  on Non-ceramic insulators in October 1997, to
  evaluate the fundamental performance of polymeric
  insulators and investigate their use status in
  Europe, North America, Australia

17
International Survey

• Reason for use High percentage goes to easy
  installation, lightweight, vandalism,
  contamination performance, easy maintenance,
  Cost, Strength, and Radio noise
• About 80 of the responses indicated the interest
  in future utilization

18
Countys service Experience

• SEC-ERB, Saudi Arabia, adopted polymeric
  insulator, on trial basis, in three different
  lines of 230 kV
• The first line started on 1995 and was affected
  by desert pollution
• The second line started on 1996 and was affected
  by semi-coastal pollution
• The third line started on 1996 and affected by
  coastal and industrial pollution

19
Countys service Experience

• The polymeric insulators presented excellent
  performance through the period of data collection
  (1995 2001
• These lines behaved well without flashovers and
  didnt need washing through the whole trial
  evaluation period

20
Countys service Experience

• Samples of these insulators were subjected later
  to mechanical, electrical laboratory testing and
  material evaluation
• The electrical and mechanical results proved the
  superior performance of these silicone rubber
  polymeric insulators

21
Countys service Experience

• There were signs of minor degradation but without
  effect on the overall performance of these
  insulators
• SEC-ERB considered the performance of the
  polymeric insulator satisfactory and cost
  effective as it helps to decrease the maintenance
  requirements

22
Countys service Experience

• Tunisian electrical company (STEG) erected more
  that 18 test stations distributed in
  representative area of the country to collect
  data about insulator performance
• After five years in service, STEG confirmed the
  satisfactory performance of the polymeric
  insulators on medium and high voltage lines

23
Countys service Experience

• Ageing aspects were noticed on the polymeric
  insulators after 18 to 24 months of services,
  which include discoloring and erosion
• Silicone rubber sheds maintain hydrophobicity
  features for longer time than EPR or EPDM rubbers

24
Countys service Experience

• Some of the units showed watertightness defects
  for the first generation insulators. Newer
  versions were working fine
• The alternate shed insulators (sheds slope lt
  18o) more suitable for desert and coastal areas

25
Countys service Experience

• Powerlink Company is the operator of the
  transmission grid in the north-eastern Australian
  State
• They are using polymeric insulators since 20
  years ago

26
Countys service Experience

• The main problem cause a worry for them is the
  bird attacks which eat part of the insulator and
  render it useless

27
Laboratory Test Methods

• Most of the laboratory tests tried to check the
  aging mechanism of the insulator housing
• The IEC 1109 defined extensive evaluation program
  for all parts of the polymeric insulator

28
Laboratory Test Methods

• The aging process and evaluation of the shed
  material are addressed through lengthy testing
  technique of 1000 hours and 5000 hours in a salt
  fog chamber
• The insulator should be subjected to electrical
  and weather parameters stress, as UV, humidity,
  heat, and rain in systematic manner for the
  defined period

29
Laboratory Test Methods

• This accelerated aging test is trying to simulate
  the effect of the harsh environment combined with
  electrical arcing stress
• The rotating wheel test is intended to evaluate
  the shed material and the interfacing between
  sheds, rod and end fittings

30
Laboratory Test Methods

• The inclined plane test is intended to evaluate
  the resistance of the material against tracking
  and erosion under HV stress
• Field inspection provides clear reference picture
  to simplify in-service inspection for the
  utilities

31
Laboratory Test Methods

• ESDD and NSDD measurements. include timely
  measurement for the level of contamination on the
  insulator surface
• Contact angle measurement provides quick
  evaluation for the hydrophobicity conditions of
  the insulator surface

32
Conclusion

• Polymeric insulators have proved itself in many
  locations through the worlds as very good
  insulator against contamination
• Silicone rubber insulating material is considered
  through laboratory evaluation and field
  experience as the most suitable for HV
  application in harsh environment

33
Conclusion

• The construction of the polymeric insulator, type
  of shed material, end fitting, fiber glass rod
  and manufacturing process are decisive factors in
  the overall insulator performance
• The GCC weather conditions are very harsh and
  require careful selection for the polymeric
  insulator

34
Conclusion

• There is clear need to adopt short and long term
  evaluation methods for the polymeric insulator in
  cooperation with researching universities and
  testing laboratories