Overview - IEC TR 62662:2010 (Guidance on brittle fracture of polymer insulators)
IEC TR 62662:2010 provides guidance for the production, testing and diagnostics of polymer (composite) insulators with respect to brittle fracture of FRP core materials. The report analyses risk factors that lead to stress corrosion cracking (SCC) - the chemical/physical process that produces brittle fracture - and gives practical recommendations to reduce in-service brittle fractures in suspension and tension insulators.
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Key topics and technical requirements
- Scope and applicability: Focused on composite insulators predominantly loaded in tensile mode (suspension and tension insulators). Guidance is written for designers, manufacturers and utilities.
- Mechanism and identification:
- Defines brittle fracture as SCC-induced sudden breakage of resin-bonded glass fibre (FRP) cores.
- Notes that brittle fracture requires both a minimum tensile stress (≈50 MPa stated) and contact with acid.
- Describes macroscopic fracture features (planar, smooth surfaces, axial delamination) and microscopic zones (mirror, mist, hackle) detectable by SEM.
- Failure mechanisms (M1–M3):
- M1 - Acid generated by electrical activity (internal/external discharges).
- M2 - Acid ingress from the environment.
- M3 - Acid generated inside the core (internal chemical sources).
- Risk assessment:
- Recommends use of FMEA (failure mode and effect analysis) to evaluate and prioritize brittle-fracture risks.
- Production, materials and sealing:
- Guidance on rod materials and production (fibreglass, resin selection, rod manufacture).
- Housing and sealing design to prevent moisture/acid ingress.
- Preventive methods and diagnostic techniques:
- Sealing systems, corona rings, material selection, housing quality, and recommended handling, transport and storage practices.
- Forensic diagnostics using fracture morphology, SEM and chemical analysis to confirm SCC.
Practical applications - who uses IEC TR 62662
- Utilities and transmission asset managers assessing insulator failure risk and inspection programs.
- Composite insulator manufacturers developing FRP cores, housings and sealing systems.
- Test laboratories conducting failure analysis and diagnostic testing for brittle fracture.
- Design engineers and procurement/specification teams writing material and production requirements to mitigate SCC risks.
Related standards and references
- IEC 61109 - Composite suspension and tension insulators: definitions, tests and acceptance criteria (normative reference).
- IEC/TR 62039 - Selection guide for polymeric materials for outdoor use under HV stress.
- CIGRE state-of-the-art reports referenced for background and material property context.
Use IEC TR 62662 when specifying production controls, inspection diagnostics, material selection and risk-assessment methods to reduce the occurrence of brittle fractures in polymer composite insulators.