1. Add a shielding layer of semi-conductive material on the surface of the conductor, which is equipotential with the shielded conductor and in good contact with the insulation layer, so as to avoid partial discharge between the conductor and the insulation layer. This layer of shielding is also known as the inner shielding layer. There may also be gaps in the contact between the insulation surface and the sheath, and when the cable is bent, the oil-paper cable insulation surface is easy to cause cracks, which are factors that cause partial discharge.
2. Add a shielding layer of semi-conductive material on the surface of the insulation layer, which has good contact with the shielded insulation layer and equal potential with the metal sheath, so as to avoid partial discharge between the insulation layer and the sheath.
In order to evenly conduct the core and insulate the electric field, 6kV and above medium and high voltage power cables generally have a conductor shield layer and an insulating shield layer, and some low-voltage cables do not have a shield layer. There are two kinds of shielding layers: semi-conductive shielding and metal shielding.
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