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.
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
Various Types of Suspension (Disc) Insulators.
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
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
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
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
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
|60-65% of Specified
E&M failing load
|Temperature||-30°C to +40°C
|-40°C to +60°C
Acceptance Criteria for T&M Test
To exclude poor quality insulators, M&E test results before and after T&M test are:
- No change in strength
- No change in fracture pattern
- No electrical puncture or no shatter
- R-3s>Specified M&E failing load
(R: mean value, s: standard deviation)
Contaminated and wet insulators display a biased leakage current having DC component. This DC component causes electrolytic corrosion and reduction of pin diameter.
Pin Corrosion of suspension (disc) insulator
- Resultant reduction of mechanical strength
- Breakage of ceramic body due to expansion of pin
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
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|
|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|
|C29.1||Electrical power insulators - test methods|
|C29.2||Wet-process porcelain and toughened glass - suspension type|
|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
Inquiry about Porcelain Insulators
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