In high-voltage systems, insulation protection is vital to reliability. When solid dielectric cable voltages reach 69kV and above, cable sheathing becomes critical.
Corrugated copper delivers high crush and shear strength.
If the weld is carefully controlled, these sheaths are impervious to moisture. Copper's high resistance to corrosion compared to aluminum significantly increases the reliability of the moisture barrier. Look for annular corrugations with swelling tapes between the insulation shield and the metal. That combination helps block longitudinal water migration. It's difficult to keep water from migrating along the continuous path formed by helical corrugations.