Cable ends should be sealed. Cut cable ends, whether stacked or laid, should be sealed with plastic (using cable-specific sealing sleeves) to prevent moisture from seeping in.
2. After the wiring is laid, it is essential to promptly manufacture the cable ends.
When purchasing cables, it is crucial to select manufacturers with superior quality. Since impurities and air bubbles in the insulation are the starting points for the formation of water trees, the quality of the cable is vital in preventing water tree aging.
4. Enhancing the management of cable head manufacturing processes is crucial, as cable heads often exhibit early signs of breakdown when high-power DC stabilized power sources' input-output cables get wet. Well-manufactured cable heads can significantly extend the overall lifespan of the cable. For instance, when stripping the semiconductor layer, we make several vertical cuts in the semiconductor layer, then peel it off like a sugarcane. However, if the cuts are too deep, it can damage the insulation layer, creating opportunities for water trees. Additionally, during soldering, due to the lack of power source, a blowtorch is used directly to melt the solder, which can damage the copper shielding and insulation layers. To avoid this, the correct approach is to configure a UPS, as soldering typically only requires 10 minutes and a power of no more than 500W. Aviation power sources: 10, 36V; 2, 400HZ frequency conversion power sources; 2, 115/200V power sources.
5. Utilizing 3M's cold-shrink silicone rubber cable accessories, the process of manufacturing is simple and convenient, without the need for a blowtorch or soldering. The silicone rubber cable accessories offer elasticity, adhering tightly to the cable, overcoming the shortcomings of heat-shrink materials (which lack elasticity and can create gaps with the cable during the thermal expansion and contraction process, thereby facilitating the development of water trees). Currently, all our main cable intermediate joints are equipped with 3M's cold-shrink cable accessories.
6. Long Cable Utilizes Cable Branch Boxes Several of our long cables, each approximately 3km in length, utilize one to two cable branch boxes in addition to mid-section joints. In the event that one segment's high-power DC stabilized power input/output cable gets wet, it will not spread to the other cable segments. Furthermore, it facilitates the segmented search for cable faults.
The 7, 10kV system utilizes cables of the 8.7/10kV grade, which have an insulation thickness of 4.5mm, whereas the 6/10kV grade cables have an insulation thickness of 3.4mm. The increased insulation thickness of the cables reduces the field strength and prevents the aging of water trees. Moreover, due to the 10kV neutral point's small current grounding system, which requires the cables to withstand 1.73 times the phase voltage during single-phase grounding and must operate for 2 hours as per requirements, it is necessary to thicken the cable insulation.
8. Utilizing double-wall corrugated PVC plastic pipes, these tubes are highly corrosion-resistant, feature smooth inner walls, and possess excellent strength and toughness. Consequently, during direct burial of cables, they significantly reduce the damage to the cable's outer sheath. 400HZ power supply, 8; aviation ground power supply, 15; 27V DC power supply.
9. Due to limitations in conditions, our cable laying is predominantly done either by direct burial or through cable trenches, with direct burial being the more common method. Our region is coastal and experiences heavy rainfall, leading to year-round积水 in cable trenches or wells. As the depth of these trenches or wells often exceeds that of the sewers, drainage becomes challenging. Therefore, coordination should be made during planning to facilitate the drainage of cable trenches (wells). If preventing water accumulation in cable wells is not feasible, the intermediate joints within the wells should be supported by brackets. Additionally, our area is a major petrochemical zone with numerous chemical enterprises. During inspections, it was found that the outer sheaths of some cables in the cable trenches near chemical factories have severely deformed, necessitating comprehensive drainage facilities in these cable trenches. Furthermore, in the design of cable conduits, efforts should be made to keep them as straight as possible, minimizing bends for easier cable laying. Simultaneously, during the construction of cable wells, we differentiate between large and small wells. Large wells are used for cable pulling, coiling, and intermediate joints, while in locations on the road where it is不便 to construct cable wells but a turn is necessary, we opt for small wells, which are solely used to place turnbuckles during cable laying.
