Cable Design

A cable is a stack of layers, and each one answers a specific failure mode rather than being there by convention: the conductor carries the current, the conductor screen smooths the electric field at the surface of the strands, the insulation withstands the voltage, the insulation screen and metallic screen control the field outside it, the bedding protects the screen from the armour, the armour takes external mechanical load, and the oversheath protects everything beneath it from the environment.

Reading a design means asking which failure each layer is there to prevent. Removing a layer to save cost only works if its failure mode has genuinely been designed out — which is why equivalent constructions across standards are compared layer by layer rather than by overall diameter.