How does the shield of a shielded control cable work?

I. How does the shielding of shielded control cables work?
Shielded control cables are suitable for shielded internal connections of electrical equipment, instruments, electronic devices and automation equipment. The conductor of a control cable is formed by stranding multiple wires. Air gaps tend to form between them and the insulation. The surface of the conductor is not smooth, which can cause electric field concentration. A shield of semi-conductive material is added to the conductor surface, which is equipotential to the shielded conductor and is in good contact with the insulation to avoid partial discharges between the conductor and the insulation. This shield is also referred to as an internal shield. There may also be gaps in the contact between the insulation surface and the sheath. When the control cable is bent, cracks may be caused in the insulating surface of the oil-paper control cable. These are factors that cause partial discharges. Partial discharges between the insulation and the sheath are avoided by adding a shielding layer of semi-conductive material to the surface of the insulation, which is in good contact with the shielded insulation and has an equipotential with the metal sheath.