QWhat should be paid attention to during the transportation and handling of cables?ADuring transportation, loading and unloading, cables and cable reels should not be damaged. It is strictly forbidden to push the cable reels directly from the vehicle. Generally, cables should not be transported and stored flat.
Before transporting or rolling the cable reel, ensure that the cable reel is firm, the cable is wound tightly, the oil pipe between the oil-filled cable and the pressure oil tank should be fixed without damage, the pressure oil tank should be firm, and the pressure indication should meet the requirements.
QWhat inspections should be carried out for the acceptance of cable lines?AA) The cable specifications should meet the regulations, the arrangement should be neat, no damage, and the signs should be complete, correct and clear;
B) The fixed bending radius of the cable, the related distance and the wiring of the metal sheath of the single-core power cable should meet the requirements;
C) The cable terminal and the middle head should not leak oil, and the installation should be firm. The oil pressure of the oil-filled cable and the meter setting should meet the requirements;
D) Good grounding;
E) The color of the cable terminal is correct, and the metal parts such as the bracket are completely painted;
F) There should be no debris in the cable trench, tunnel, and bridge, and the cover should be complete.
QHow many projects can cable engineering be divided into?A(1) Construction site transportation: including the loading and unloading, transportation and empty vehicle return journey of engineering materials from the warehouse to the construction site.
(2)Local engineering: including road excavation, tunnel, trench construction, etc.
(3)Laying engineering: including laying, intermediate head production, lift cover plate, buried pipe, school tide, tractor head production, etc.
(4)Two-end engineering: including the production and installation of support, suspension bridge and its foundation, the production of terminal heads, the installation of oil pressure and signal devices, and the electrical performance testing of various types.
(5)Stopping works: including the production of oil-filled cable stop heads, the installation of fuel supply tanks, automatic drainage and signal devices, etc.
(6) Grounding engineering: including installation of insulation joints, transposition boxes, protectors, and grounding boxes.
QWhat tests and inspections should be carried out on power cables before laying?ABefore laying, check whether the type, specification and length of the cable meet the requirements and whether there is external force damage. Low-voltage cables use a 1000V megohmmeter to remotely measure the insulation resistance, and the resistance is generally not less than 10MΩ. High-voltage cables use a 2500V megger to measure the resistance. Generally not less than 400MΩ.
QWhat are the factors that determine the long-term allowable current carrying capacity of the cable?A(1) The long-term allowable working temperature of the cable;
(2) The heat dissipation performance of the cable itself;
(3) The condition of the cable installation and the heat dissipation conditions of the surrounding environment.
QAccording to the difference of insulation and protective layer, what are the main types of commonly used low-voltage power cables?A(1)Oil-impregnated paper insulated lead-clad (or aluminum-clad) power cable;
(2)Non-drip oil-impregnated paper insulated power cable
(3)PVC insulated and sheathed power cable;
(4)Cross-linked PVC insulated and PE sheathed power cable;
(5)Cross-linked PVC insulated and sheathed power cable;
(6) Rubber insulated power cables.