▎ 摘　　要

NOVELTY - Polypropylene cable protective layer comprises a dielectric layer, a buffer layer and an insulating layer from inside to outside. The thickness of the dielectric layer is 5-12% of the thickness of the polypropylene cable protective layer. The thickness of the buffer layer is 17-25% of the thickness of the polypropylene cable protective layer. The dielectric layer is obtained by wrapping polypropylene film A. The buffer layer is obtained by wrapping polypropylene film B and the insulating layer is obtained by wrapping polypropylene film C. The polypropylene films A, B and C comprises polypropylene, graphene oxide and maleic anhydride grafted polypropylene. The thickness of the polypropylene film A is 0.05-0.2 mm. The thickness of the polypropylene film B is 0.05-0.2 mm. The thickness of the polypropylene film C is 0.05-0.2 mm USE - Used as polypropylene cable protective layer. ADVANTAGE - The polypropylene cable protective layer forms a dielectric gradient; greatly improves the electrical strength of the cable; significantly reduces the thickness of the insulating layer; achieves the balance of electrical strength, mechanical toughness and thermal conductivity of power cables; improves the insulation strength of power cables; increases the voltage level and increases the power transmission energy and reduces the mechanical toughness and heat dissipation capacity of the power cable. DETAILED DESCRIPTION - Polypropylene cable protective layer comprises a dielectric layer, a buffer layer and an insulating layer from inside to outside. The thickness of the dielectric layer is 5-12% of the thickness of the polypropylene cable protective layer. The thickness of the buffer layer is 17-25% of the thickness of the polypropylene cable protective layer. The dielectric layer is obtained by wrapping polypropylene film A. The buffer layer is obtained by wrapping polypropylene film B and the insulating layer is obtained by wrapping polypropylene film C. The polypropylene film A comprises 100 pts. wt. polypropylene, 8-10 pts. wt. graphene oxide and 0.5-5 pts. wt. maleic anhydride grafted polypropylene. The thickness of the polypropylene film A is 0.05-0.2 mm. The polypropylene film B comprises 100 pts. wt. polypropylene, 4-6 pts. wt. graphene oxide and 0.5-5 pts. wt. maleic anhydride grafted polypropylene. The thickness of the polypropylene film B is 0.05-0.2 mm. The polypropylene film C comprises 100 pts. wt. polypropylene and 0.5-5 pts. wt. maleic anhydride grafted polypropylene. The thickness of the polypropylene film C is 0.05-0.2 mm. INDEPENDENT CLAIMS are also included for: (1) a cable comprising a conductor (1), a polypropylene cable protective layer and an outer shielding layer (5) in sequence from the inside to the outside; and (2) preparing polypropylene cable protective layer comprising (a) wrapping the polypropylene film A into a dielectric layer, (b) wrapping the polypropylene film B along the dielectric layer to obtain a buffer layer, (c) wrapping the polypropylene film C along the buffer layer to obtain an insulating layer and (d) hot pressing at 160-180degrees Celsius, where the hot pressing direction of the hot pressing comprises multiple hot pressing directions are symmetrical in the center and perpendicular to the circumference of the polypropylene cable protective layer and the pressure deviation of the multiple hot pressing directions is not more than 2%. DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the cable. Conductor (1) Outer shielding layer (5)