Composite insulators were introduced in the late sixties. The basic idea consists of the combination of different materials, which perform different duties in the insulator function corresponding to their particular strength and properties.1-400 kV polymeric insulators or composite silicone rubber insulators are manufactured conforming to international standards & specifications. Earlier insulators were made up of ceramic or glass only but with the advancements in technology the usage of composite insulators has grown to prevent line flash-over triggered by pollution.
Composite insulator’s shed and sheath are be made of high temperature vulcanizing (HTV) type silicone rubber, having silicone polymer content by weight 30% minimum. Alumina Tri hydrate (ATH) is used as filler. The filler is properly mixed with silicone compound to ensure the uniform distribution. Thickness of sheath shall be minimum 3 mm and shall have excellent hydrophobic and anti-tracking properties.
The material shall conform to the tests specified in IEC or other technical standard equivalent. The material preferably shall be such that it should not attract birds or other rodents at storage location or on the line. In some country, like India, the thickness of shed at edge should not be less than 2.5mm to minimize the external damage. The strength of shed to sheath interface shall be greater than the tearing strength of polymer. And cleaning methods of silicon rubber sheds shall be paid attention to.
Composite insulators can be divided into: line composite insulators and power stations, electrical composite insulators. Can also be divided into rod-shaped suspension composite insulators, needle composite insulators, cross-arm composite insulators, pillar composite insulators, wind-proof partial composite insulators.
In the early years, insulators were mostly used in utility poles. With the development of technology, many disc-shaped insulators were hung on one end of the high-voltage high-voltage wire connection tower. It was added to climb the electric insulation interval, usually made of glass or ceramic. It is called an insulator. Insulators play two fundamental effects in overhead transmission lines, namely supporting the conductors and preventing current from returning to the ground. These two effects are necessary to ensure that the insulators should not fail due to various electromechanical stresses caused by changes in environmental and electrical load conditions. Otherwise, the insulator will not have a significant effect, which will jeopardize the operation and operation life of the entire line.
Features of Composite Insulators,Polymer Composite Insulators
Light weight (65-80% less than ceramic insulator)
Superior anti-tracking properties
Long term surface hydrophobicity
Suitable for polluted environment, salty atmospheres etc.
Silicon rubber sheds provide perfect hydrophobic performance, good resistance to ageing, tracking and erosion
Stable behaviour at extreme climatic conditions
High mechanical strength
High flexibility and shock resistance
– High tracks and power arcs resistance
– High safety where vandalism is a problem
– High creepage on a short length
– Excellent behavior in polluted areas
Ease of installation (easier handling with lighter equipment and labour at the job site)
Resistance to breakage and vandalism, practically unbreakable
Compliance with IEC 61109, ANS C29-11-1989
The end fittings are typically made of metal, such as forged steel or aluminum. For line insulators, a high degree of standardization has been achieved for the end fittings, which enables the easy replacement of existing conventional insulators by composite solutions.
The fiberglass reinforced resin rod is responsible for bearing the mechanical loads, which can be tension, bending or compression, or a combination of all three, depending on the application and load scenario.