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Suspension Insulators

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Overview

Suspension insulators support transmission lines on steel towers

Insulators are essential to the safe and stable distribution of electricity generated at power plants. Suspension insulators support transmission lines on steel towers, isolating the lines from the tower. They play a key role in the safe supply of electricity.
Based on the transmission voltage and usage environment, suspension insulators are used in configurations of two or more.

Features

NGK Suspension (Disc) Insulators

NGK Suspension (Disc) Insulators have been used successfully in more than 100 countries and in particular have a majority in EHV, UHV and HVDC transmission lines.

Available for any voltage and contamination level by changing number of insulators

  • Mechanical strength up to 530kN
  • High reliability through accumulated technology
  • Excellent long-term performance

Product Lineup

Various Types of Suspension (Disc) Insulators.

Normal type for light contamination
Normal type for light contamination
Fog type for heavy contamination
Fog type for heavy contamination
DC Fog type for DC transmission line
DC Fog type for DC transmission line
Aero dynamic type for desert contamination
Aero dynamic type for desert contamination

Application

1000kV AC T/L (Japan)
1000kV AC T/L (Japan)
1000kV AC T/L (Japan)
1000kV AC T/L (Japan)
500kV AC T/L (China)
500kV AC T/L (China)
±500kV DC T/L (USA)
±500kV DC T/L (USA)
765kV AC T/L (Korea)
765kV AC T/L (Korea)
±250kV DC T/L (New Zealand)
±250kV DC T/L (New Zealand)

High Reliability

High reliability is achieved by long-term experience and accumulation of technology.

Selected High Quality Raw Material

High strength porcelain insulators require not only higher amount of alumina but also

  • Management of mining site
  • Sufficient technology of material analysis
  • Strict incoming inspection - Use only selected material
  • Fine and uniform distribution of particles
Selected High Quality Raw Material

Optimum Design Engineering

  • Straight head design with less stress concentration
  • X-3s >= M&E rating with stable mechanical strength (X: average, s: standard deviation in M&E test*)
  • Light weight and compact design
  • *M&E Test: Electromechanical failing load test as per IEC 60383-1
Optimum Design Engineering
Distribution of Mechanical Strength in M&E Test

Advanced Manufacturing Technology

  • Automated mass production system
  • Uniform quality by continuous firing and production control
  • Control of porcelain thermal expansion
  • Forming without material damage
  • Accurate assembling without stress concentration
Forming
Forming
Assembling
Assembling

Strict Quality Control

In addition to ISO 9001 certified,

  • Routine hydraulic pressure test developed by NGK - Effective elimination of manufacturing defects
  • Total quality activities of preventive maintenance

Hydraulic Pressure Test

Principle
Principle
Test Situation
Test Situation

Excellent Long-Term Performance

Long-Term Performance Evaluation

Thermal-Mechanical (T&M) performance test as per IEC 60383-1 or ANSI C29.2 is to evaluate long-term reliability of insulators.
As these standards specify minimum requirements only, all NGK insulators have been confirmed to pass modified T&M test.

Test Method IEC Pub. 60383-1 NGK Method
Load 60-65% of Specified
E&M failing load
(24-hour cycle)
60-65% of Specified
E&M failing load
(1-hour cycle)
Temperature -30°C to +40°C
(24-hour cycle)
-40°C to +60°C
(8-hour cycle)
Duration 4days 15days

Acceptance Criteria for T&M Test

To exclude poor quality insulators, M&E test results before and after T&M test are:

  1. No change in strength
  2. No change in fracture pattern
  3. No electrical puncture or no shatter
  4. R-3s>Specified M&E failing load

(R: mean value, s: standard deviation)

Acceptance Criteria for T&M Test

Zinc Sleeve

Contaminated and wet insulators display a biased leakage current having DC component. This DC component causes electrolytic corrosion and reduction of pin diameter.

Zinc Sleeve

Pin Corrosion of suspension (disc) insulator

  • Resultant reduction of mechanical strength
  • Breakage of ceramic body due to expansion of pin
Pin Corrosion of suspension (disc) insulator

NGK developed Zinc Sleeve to prevent pin corrosion.

  • Galvanically positive
  • Large potential difference from iron
  • Sacrificial electrode at cement boundary
  • Bonded area of sleeve: Min. 80% of sleeve/pin interfacial area to prevent corona discharges
  • Purity of zinc >- 99.8% to prevent granular corrosion
NGK developed Zinc Sleeve to prevent pin corrosion.

Test & Standard

NGK suspension (disc) insulators meet the requirements and tests of the following standards.

IEC Standard and Technical Report

60060-1 High-voltage test techniques, Part 1: General definitions and test requirements
60120 Dimensions of ball and socket coupling of string insulator units
60305 Characteristics of insulator units of the cap and pin type
60383-1 Insulator units - Definitions, test methods and acceptance criteria
60383-2 Insulator strings - Definitions, test methods and acceptance criteria
60437 Radio interference test on high-voltage insulators
60471 Dimensions of clevis and tongue coupling of string insulator units
60507 Artificial pollution tests on high-voltage insulators to be used on a.c. systems
60575 Thermal-mechanical performance test
60797 Residual strength of string insulator units
60815 Guide for the selection of insulators in respect of polluted conditions
61211 Puncture testing
61245 Artificial pollution tests on high-voltage insulators to be used on d.c. systems
61325 Insulator units for d.c. systems - Definitions, test methods and acceptance criteria

ANSI Standard

C29.1 Electrical power insulators - test methods
C29.2 Wet-process porcelain and toughened glass - suspension type

CAN/CSA Standard

C411.1 AC suspension insulators

EHV & UHV Service Experiences

Transmission lines with higher system-voltage carry greater power flow. They serve the role of trunk feeder in the delivery of power. Instability in EHV and UHV line operation may cause great negative impact on the entire power system.

Thus, insulators for EHV and UHV transmission lines require not only endurance against higher electrical and mechanical stress but must also ensure uniformly high quality to maintain the reliability of system operation.

NGK insulators have been the choice for the majority of the world's EHV and UHV transmission projects because of quality and performance. Successful long-term service experience in higher system voltage illustrate the reliability and quality of NGK suspension insulators.

  • 1,000 kV Kashiwazaki - Karima - Higashi Yamanashi, Japan
  • 1,000 kV Minami Iwaki - Nishi Gunma, Japan
  • 800 kV Anpara - Unanao, India
  • 735 kV Levis - Des Castos, Canada
  • 800 kV Kishenpur - Moge, India
  • 800 kV Guri - Sur - Arenosa, Venezuela
  • 765 kV Amos - North Protrvilk, U.S.A

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