Composite Insulator - Long Rod

Composite insulator are also named polymer insulator, silicone rubber insulator, composite long rod insulator etc. According to how insulators are installed they can be classified as suspension type composite insulator, tension type insulator.

The complete composite insulators consist of a ECR Fiberglass Reinforced Plastic (FRP) core having superior electrical and mechanical performance, sheath (housing), sheds and metal end fittings.

Main Feature of Composite Insulators

Composite insulators are designed according to the basic insulation levels (power frequency withstand voltage, BIL & BSL etc.) as specified by customers. For installations at altitudes higher than 1000 meter, the insulation levels shall be corrected as per IEC 62271-1. The electrical withstand values shall be met with combined power arc protection devices including electric field control corona rings installed.

Mechanical and Electrical characteristics of composite insulators are the base designing requirements.

Core

The core is made of Electrical Grade Corrosion (ECR) Fiberglass Reinforced Plastics (FRP) Rod, with acid and high temperature resistance performance.

To reduce the risk of brittle fracture, the FRP core of composite insulators will be electrical corrosion-resistant (ECR) glass rod that shall achieve the specified electrical and mechanical characteristics. The FRP core will be resistant against hydrolysis under service conditions.

Housing

Housing (sheath and weather sheds) is made of high temperature vulcanized (HTV) silicone rubber, which has excellent hydrophobicity and ant-tracking performance. The composite insulators have hydrophobicity of silicone rubber material classified Hydrophobicity Class 1 (HC-1) . or it can be described as receding water contact angle will be 80° or more.

The composite insulators sheath and sheds material have a chemical structure of 100 percent silicone rubber before adding fillers. The finished product will be ultraviolet (UV) radiation exposure resistant. The finished product shall not be affected by atmospheric conditions due to weather, proximity to the coast, fumes, ozone, acids (particularly sulfuric acid present in the prevailing environment of oil field areas in the region), alkalis, dust or rapid changes to air temperature. There shall be no material degradation such as development of surface cracks and increase in surface hardness, etc.

The track resistance of the sheath and shed material shall meet the requirements of IEC 60587 Method 1 Class 1A4.5 or 1B4.5 or Method 2 Class 2A4.5.

The sheath and sheds material of insulators fabricated from high temperature vulcanized silicone rubber shall have a Shore ‘A’ hardness of not less than 60.

The composite suspension and tension insulators shall be of alternating shed design with aerodynamic type profile and without any under-ribs designed in accordance with IEC/TS 60815-3. Sheds shall be at intervals to provide optimum electrical performance and the shed design shall provide a protected bottom surface that tends to keep dry in wet conditions. In accordance with IEC/TS 60815-3, the shed spacing (defined as the minimum vertical distance between two similar points of successive sheds of the same diameter) and the ratio of shed spacing to shed overhang/projection shall be more than 40 mm and 0.80 respectively.

Top end-fitting, Bottom end-fitting

End-fittings are made by forged steel or ductile cast iron (treaded with hot dip galvanizing). end-fittings are fastened to the core by precise crimping method.Metal parts are made of the best commercial grade of malleable iron, ductile iron or steel, and galvanized in accordance with the Specification.

Interface

Housing is firmly bonded to core by high performance bonding agent to protect the core from getting damaged by acid, water, alkali and UV rays etc.

End-fittings have special sealing groves and filled by HTV silicone rubber during molding injection, which will prove excellent sealing properties.