Relevant technical requirements for installation of power cable accessories
【Abstract】：Power cable accessories are not equal to other industrial products. Other factories cannot supply complete power cable accessories products. Only the materials, components or components of accessories are supplied. It is necessary to pass the field equipment on the cable to form a real product. Therefore, it is necessary to insist that the power cable accessories in operation have excellent functions and have the same insulation level as the cable itself. It not only requires reasonable design, Accessories with excellent material properties and reliable processing quality also require correct on-site equipment technology and careful operation. This requires not only the staff engaged in cable accessories equipment to grasp the relevant knowledge of cable accessories, but also to have corresponding process standards to strictly control. |
Generally speaking, the general disadvantage of the insulation level in the cable line is that the joint parts are affected by external factors. Most of the faults (non-external force damage) also occur on the joint accessories of the cable. Whether in theory or in practice, it can be proved that the joint part is the weak link of the cable line, so the quality of the cable joint is directly related to the operation safety of the cable line, so the power cable accessories must meet the following technical requirements.
Relevant skill requirements for power cable accessories:
1. Regulations of common cable terminals in electrical installations
The cable terminal shall comply with the relevant provisions ofElectrical Equipment Engineering Construction and Inspection Standards; in terms of electrical equipment.
(1) The phase color of the cable terminal. The cable terminals should be clearly marked with the phase color, that is, A-phase yellow, B-phase green, C-phase red, and consistent with the phase of the system.
(2) Safe clear distance. The exposed metal parts (including the shielding cover) at the end of the cable terminal between the conductors of different phases and between the live parts of each phase and the ground should conform to the specified value of the safe clearance of indoor and outdoor power distribution equipment.
2. Regulations for grounding wires of common power cable accessories of 35kV and below
When the cable has insulation breakdown or system short-circuit, the fault current in the cable conductor will lead to the earth through the metal shielding layer of the cable. For the safety of people and equipment, it is necessary to install grounding wires at the cable terminals and joints according to regulations. At the cable terminals and joints. According to the provisions of theConstruction and Inspection Standards for Grounding Equipment;, the metal shells of the cable terminals and joints, the metal shielding layer of the cable, the casing layer, the metal bracket of the cable, the grounding wire or the grounding row should be grounded. , The metal shielding layer and the Kaede layer of the connector need to be connected with an equipotential connecting line.
The ground wire of the cable terminal and the equipotential connection wire of the connector are generally 25mm tinned copper braided wire. The metal shielding layer at the two ends of the joint needs to be connected with steel mesh.
In the 6-10kV cable line, when the cable is selected for zero-sequence maintenance, when the cable grounding point is below the zero-sequence current transformer, the grounding wire should be directly grounded. When the grounding point of the cable is above the zero-sequence current transformer, the grounding wire should be an insulated wire and be grounded through the zero-sequence current transformer.
3. Anti-corrosion and mechanical maintenance requirements for joints in common cables of 35kV and below
When making cable joints, due to technical requirements, it is necessary to strip off a section of the cable outer sheath and the Kaede layer, and appropriate materials should be used to replace the original cable outer sheath as an anti-corrosion and mechanical maintenance structure.
(1) Commonly used anti-corrosion materials are: one is kaiseki tape; the other is heat shrinkable tube, both ends are covered with waterproof tape and wrapped in two layers, and then wrapped with a layer of cat rubber tape.
(2) Mechanical maintenance of cable joints. The commonly used joint mechanical maintenance material for direct buried cables is a reinforced concrete maintenance box, and the open space in the box is filled with fine cat soil or fine sand. The new connector maintenance box is made of rigid plastic or epoxy glass Rui steel, which is popular with users due to its compact structure and light weight.
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