Composite Insulators

Composite Insulators Composite insulators are typically non ceramic insulators have different chemical compositions typically fibreglass rod with rubber (EPDM or silicon) sheath and weather sheds. They are use in HDPE line insulator applications. Cycloaliphatic (epoxies) station applications. Metals components normally crimped. There are following types of composite insulators . 1. Silicon rubber (SR) – Room temperature vulcanizing (RTV), High temperature vulcanizing and liquid rubber (LSR). 2. Ethylene Propylene rubber (EPR) , Ethylene Propylene Monomer (EPM), Ethylene Propylene Dien Monomer (EPDM). 3. Epoxy Resin – Bisphenol, cycloaliphat 4. Polyurethene 5. Polufluor carbons – Teflon, PTFE

Manufacturing Design First we have to design the insulators according according to our needs. 22kV 2 Sisk Equivalent Composite Suspension/Strain Insulator Socket/Ball

22kV Composite Suspension/Strain Insulator Clevis/Tongue

11 To 44kV 40kN Composite suspension/Strain Insulator Socket/Ball

66 To 132kV 40kN Composite Suspension/Strain Insulator Socket/Ball

Moulding After designing we have the different moulding methods in which we mould the insulators using different moulding materials .There are three types of moulding. 1. Compression moulding 2. Transfer moulding 3. Injection moulding

Materials for Housing 1. Silicone Rubber HTV, RTV, LSR 2. Ethylene Propylene Rubbers: EPDM, EP silicone alloys 3. Epoxies: Cycloaliphatic epoxies 4. Polyolefins : Ethylele Vinyl Acetate (heat shrinkable)

Hydrophobicity Ability of surface to prevent water filming – water drops beading. Often misunderstood property 1. Hydrophobicity loss does not mean failure. 2. All polymers are initially hydrophobis

3. Hydrophobicity is reduced during service 4. Dirt, UV, Corona , Discharges 5. For EPs , Epoxy, the above will eliminate e liminate hydrophobicity hydrophobicity 6. For silico silicones nes,, only excess excessive ive corona corona and and strong strong dischar discharge ge can destro destroyy hydrop hydropho hobic bicity ity locally.

Recovery Desireable as high surface resistance restored Mainly due to diffusion of LMW polymer chains from bulk to surface Recovery ability different for polymers, Silicones highest – high surface resistance obtained even before visible recovery accurs. Recovery ability lost for EP, epoxy when dirty.

Difference between Porcelain and Composite Insulators Porcelain 1. They are brittle and require careful handling. 2. Materials very resistant to UV,contaminant degradation,electric field degradation. 3. Materials strong in compression,weaker in tension 4. High modules of elasticity – stiff  5. Havier than NCIs 6. Limited flexibility of dimensions 7. Process limitations on sizes and shapes 8. Applications/handling Applications/handling methods generally well understood. 9. Surface of these insulators are hydrophilic. i.e continuous film of water form leads to the increase in leakage current.

Composite 1. Hydrophobic materials improve contamination performance. 2. Strong in tension ,weaker in compression. 3. Deflection under load can be an issue. 4. Lighter – easier to handle 5. Electric field stresses must be considered

6. Material properties have been improved e.g standardized product lines now exist. Balancing act – leakage distance/field distance/field stress – take advantage of hydrophobicity. Application parameters still being developed. Line design implications(lighter weight, improved shock resistance). 7. 90% weight reduction 8. Reduce breakage 9. Lower installation costs 10. Aesthetically more pleasing 11. Improve resistance to vandalism 12. Improved handling of shock loads 13. Improve power frequency insulation 14. Improved contamination performance