Conducting wire core
Copper wire is usually used in conducting wire core material, and its cross section is selected according to the rated current, allowable pressure drop, short circuit capacity and so on. When selecting core structure, we should consider the problem of seawater penetration after failure. Generally, water plugging measures such as pressure gathering, welding, water sealing material and so on can be used.
The thickness of the insulating layer should meet four requirements: the DC cable for rated DC voltage and no load field at the surface of the conductor should be allowed under the value; for the rated DC voltage, full load at the outer wrapping field should be within the allowable value; the tolerance of the impulse test voltage at rated current; 4 next, the temperature of the conductor shall be within the allowable value below. In general, several insulation thickness can be assumed to be calculated, and the most suitable insulation thickness can be selected.
Outer protective layer
Because the DC cable does not have induction voltage in the metal sheath and armour, there is no problem of the loss of the sheath. The structure of the protective layer is mainly to consider the protection of machinery and to prevent corrosion, especially for the submarine cable.