Some customers have misunderstandings about the power cable's ampacity and theoretical ampacity in the process of designing low- and medium-voltage power cables. It is believed that the power cable can be used only if it meets the actual operating capacity of the equipment, and often neglects the actual laying conditions. Correcting the actual operating ampacity of the cable laid a hidden danger for the cable accident.
For example, for example, more than 50 10kV power cables for power transmission in the plant area are all individually pierced into thick white PVC plastic pipes. They are piled up and stacked in five layers with no gaps. They are laid directly and buried in depth. The soil is buried to a depth of about 1 meter. The number of power cables laid on the floor is 10, and the distribution section of the entire cable discharge pipe in the ground is basically arranged in a rectangular manner. The total length of the cable line is about 1 km. There are two cable wells in the middle of the cable joints to facilitate the maintenance of the cable line. When these cables were continuously energized and operated for about one day, the unpleasant pyrolytic smell due to the heat generated by the plastic cable was discharged from the cable wellhead. After a week, the power cables were successively thermally broken down. Finally, the entire 10kV power cable line cannot be used normally. The occurrence of such incidents is a lack of scientific understanding of the actual operation of the cable using ampacity, resulting in power cable accidents.
Various types of specifications of low and medium voltage power cables have a theoretical calculation of current carrying capacity. Multiple cables penetrate PVC plastic pipes and are laid without any gap. The ambient thermal resistance coefficient of each power cable is directly buried in the power cable. The way of laying ground has greatly increased. Therefore, for the initial design of the cable laying project, the actual thermal resistance after laying the cable must be fully taken into account, and the corrective design must be carried out in time. Otherwise, the economic loss caused is enormous.
When multiple power cables are placed side by side with no gaps, stacking, laying, and burying directly, when one of the power cables fails, the adjacent one or more cables may be burned, causing the accident to spread and expand. At the same time, it will also lead to thermal breakdown. Too many direct-buried roots in power cables are not conducive to actual maintenance and excavation of cable faults. Because of the large number of cables, the chance of mechanical damage to the cables during excavation will be greatly increased. At the same time, when excavating faulty cables, adjacent power cables It may be in a power-on state, and the range of blackouts caused by electric shock accidents and secondary accidents is likely to expand.
For multiple power cables buried at the same time, the number of roots should preferably be controlled to 6 or less. During the laying process, the distance should be as far as possible to provide sufficient space for heat dissipation in the power cable. When the cable is selected, heat must be dissipated to the surrounding soil or sand. The performance is fully considered, and the thermal resistance coefficient is calibrated to ensure the normal and safe use of the power cable so that its service life can be fully utilized.
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