Field Ageing Behaviour of Long Rods

The study “Field Ageing Behaviour of Long Rods Analysed According to Cigré TB 306” by Markku Ruokanen and Marek Vrabec (Insulation Technology Group) examines how the remaining lifetime of ceramic long rod insulators can be reliably assessed in aging transmission networks.

The research focuses on the effectiveness of ageing evaluation methods defined in Cigré TB 306, with special attention to routine thermal cycling tests used by Transmission System Operators as a practical alternative to complex thermo-mechanical testing. Through laboratory testing and detailed microstructural analysis of C-120 and C-130 porcelains, the study evaluates the influence of material composition on mechanical strength and crack growth resistance.

The study concludes that high alumina content and an optimized corundum–mullite microstructure are key to preventing mechanical ageing. Long rod insulators manufactured with optimized ceramic bodies since the 1990s show no significant loss of strength even after decades in service, underlining the importance of material quality in lifetime assessment.

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Field Ageing Behaviour of Long Rods Analysed According Cigré TB 306