Flame-retardant XLPE insulated and PVC sheathed copper […]
Flame-retardant XLPE insulated and PVC sheathed copper core power cable
1. ZR-indicating flame-retardant cable, the flame-retardant grade is divided into three categories: A, B, C, among which the A-type flame-retardant grade is the highest; generally ZR is ZRC; ZRC or ZR is flame-retardant C, ZRB or ZB It is flame retardant type B, ZRA or ZA is flame retardant type A;
2. YJ-cross-linked polyethylene insulation
3. V-PVC sheath
Cross-linked polyethylene insulated cable is a kind of cable suitable for power distribution network and other fields. It has the incomparable advantages of PVC insulated cables. It has simple structure, light weight, good heat resistance, strong load capacity, non-melting, chemical corrosion resistance, and high mechanical strength.
Cross-linked polyethylene insulated cables use peroxide cross-linking methods to make polyethylene molecules change from linear molecular structure to three-dimensional network structure, and from thermoplastic materials to thermosetting materials. The working temperature has increased from 70°C to 90°C. Improve the current carrying capacity of the cable. XLPE insulated cables have the following advantages:
1. Heat resistance: XLPE with three-dimensional network structure has excellent heat resistance. It will not decompose and carbonize below 300℃, the long-term working temperature can reach 90℃, and the thermal life can reach 40 years.
2. Insulation performance: XLPE maintains the original good insulation properties of PE, and the insulation resistance is further increased. The dielectric loss tangent value is very small, and is not greatly affected by temperature.
3. Mechanical properties: Due to the establishment of new chemical bonds between macromolecules, the hardness, stiffness, wear resistance and impact resistance of XLPE have been improved, thereby making up for the defect of PE being vulnerable to environmental stress and cracking.
4. Chemical resistance: XLPE has strong acid and alkali resistance and oil resistance. Its combustion products are mainly water and carbon dioxide, which are less harmful to the environment and meet the requirements of modern fire safety.
Cross-linked polyethylene insulated power cables cause moisture or moisture to enter the cable insulation during installation and operation, mainly in the following situations.
(1) The sealing of the cable end cap is not tight or the cable end cap is damaged by external force during the process of cable transportation and laying.
(2) The cable sheath is damaged by external force during cable transportation or laying.
(3) During the cable experiment or operation, the cable insulation breakdown damages the cable sheath.
(4) The cable accessories (especially the intermediate joints when directly buried) are not tightly sealed. Once moisture or moisture enters the cable insulation from the end of the cable or the outer sheath of the cable, it may penetrate longitudinally from the gap shielded by the outer insulation copper wire or from the gap between the conductors, endangering the entire cable system. The damp cable will produce "water tree branch" phenomenon under the effect of high electric field, which will reduce the insulation performance of cross-linked polyethylene, and finally lead to cable insulation breakdown. Therefore, it is necessary to dehumidify the damp cable.