What’s hiding inside high-voltage AC cables? 

High-voltage alternating current (AC) cables are vital for transmitting electricity from offshore wind farms and other marine energy facilities to land-based grids. Manufactured in 100-meter sections, they contain copper or aluminium conductors protected by multiple layers of insulation and shielding. Any structural or chemical defect can cause severe power outages, costly repairs, and safety hazards, making strict quality control and detailed materials testing indispensable.
The NANOCHEM team at SDU applied advanced methods like micro-computed tomography (µCT) and confocal Raman imaging to study the 3D structure and chemical composition of a cable cross-section.
The sample, roughly 1 cm thick and 10 cm in diameter, was found to consist of four main layers: the outer insulation, cross-linked polyethylene, inner insulation, and a concentric aluminium rod core (see Figure a).

This study revealed the presence of unexpected fibres made of either polystyrene or aramid, situated between the aluminium core and the inner insulation layer (see Figures b and c). Furthermore, unrecognised materials were found at the interfaces of the insulation layers. The investigation also uncovered millimetre-scale inhomogeneities and voids within the aluminium rods.
These findings emphasise the crucial role of advanced analysis and early detection of impurities and inconsistencies in high-voltage cable manufacturing and material selection. While failure analysis enhances quality and reliability, upscaling these methods remains challenging. Ongoing collaboration and evaluation are essential to ensure the safety and performance of energy infrastructure.