1
What should be noted for direct burial laying? Under what circumstances is it adopted?
For direct burial laying, it is necessary to consider whether the cable is susceptible to damage from external impact.
1. If it will not be subject to significant impact, direct laying is acceptable.
2. If it may be subject to relatively large impacts, but the intensity can be controlled within a certain range, armored direct burial can be considered.
3. If the external force is greater, protective conduits need to be used, which can be set locally (for example, where crossing roads).
Advantages and disadvantages of direct burial laying of cables:
Advantages: Convenient laying, saving materials and labor,
Disadvantages: Inconvenient maintenance. If maintenance is needed, the covering soil must be dug open. It is only recommended for places where maintenance is not considered, or where this maintenance method is acceptable. When direct burying, it is generally necessary to lay yellow sand underneath.
Question 1: How to find the fault point when a direct-buried cable is grounded?
Answer: Use a cable fault locator.
Question 2: Do direct-buried cables need cable manholes?
Question supplement: In cable laying within a factory area, using armored cables for direct burial, do cable manholes need to be added at road crossings and where entering workshop power distribution rooms? Does the municipal 10KV cable entering the factory area need a cable manhole?
Answer: When there are 6 or fewer cables, cable manholes may not be needed. If there are many cables, manholes are set for easy replacement and addition of cables. The municipal 10KV cable entering the factory area does not need a cable manhole; it can be directly buried from the terminal pole to the high-voltage distribution cabinet.
Question 3: How to lay temporary cables on a construction site?
Question supplement: A unit is building a new factory. The construction transformer and high-voltage lines are far from the construction center. Since it is a steel structure factory, overhead lines cannot be used to avoid conflicts with steel structure installation. Only low-voltage cables can be used to lead from the transformer to the first-level distribution box at the construction site, and then distribute to the second-level distribution boxes of various construction units. How should this low-voltage cable be laid? Should it be directly buried or placed directly on the ground?
Answer: It is strictly forbidden to lay directly on the ground. This low-voltage cable should be laid by direct burial.
2
What should be noted for laying in conduits? Under what circumstances is it adopted?
Laying cables in conduits, compared to direct burial, is more convenient for later maintenance and adding circuits. For cables laid in conduits, some spare conduits can be considered to prepare for future line maintenance and capacity expansion.
1. When laying in conduits, cable manholes need to be considered when the line has large turning angles or long straight sections.
2. When the number of cables is small and the diameter is small, cable handholes can be used;
3. When there are many cables and large diameters, cable manholes need to be considered. Cable manholes can be constructed according to standard drawings. In addition to standard drawings, many small crossing manholes can be directly built with bricks or cast concrete, in which case drainage holes should be considered at the bottom.
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