The method of cable installation plays a crucial role in the performance and maintenance of power systems. Common methods include direct burial, pipe laying, shallow trenching, cable trenching, tunneling, and aerial installation. Among these, tunneling and trenching are considered the most effective due to their ease of access for maintenance and construction. In many developed cities, public utility tunnels are integrated into urban planning, which has proven to reduce repeated excavation and investment. However, this approach requires a significant initial investment, making it less common in China due to economic and logistical constraints. Direct burial and shallow trenching are more cost-effective but pose challenges for future maintenance. If a fault occurs, re-excavation is often necessary, which can be time-consuming and disruptive. Therefore, the selection of an appropriate cable laying method should consider factors such as environmental conditions, cable type, quantity, long-term development, and technical and economic feasibility. When choosing cables, various types are available, including oil-filled, PVC-insulated, and XLPE cables. With advancements in manufacturing technology, XLPE cables have become the most widely used due to their durability and efficiency. The selection should be based on the specific environment and application requirements. For direct burial or shallow trenching, cables with reinforced steel armor may be necessary to ensure mechanical protection. Selecting the right cross-sectional area for the cable is essential for balancing cost, energy loss, and operational safety. A too small cross-section can lead to overheating and voltage drops, while a larger one increases initial costs. It’s important to follow technical guidelines such as the "Technical Guidelines for Urban Medium and Low Voltage Distribution Network Transformation" to ensure compliance with thermal stability and voltage drop standards. In three-phase four-wire low-voltage systems, the neutral wire's cross-sectional area should match that of the phase wires to prevent unbalanced loads from causing voltage fluctuations and increased losses. This helps maintain system efficiency and reliability. As power cable usage grows, so does the need for automation in distribution networks. Cable networks can be standalone or part of hybrid systems. Automation requirements must be met according to technical guidelines, ensuring future scalability and compatibility with new technologies. Even if full automation isn't feasible now, equipment choices should allow for future upgrades. During cable installation, several issues must be addressed. Eddy currents can form around metal supports or conduits, especially in high-current systems, leading to overheating and insulation failure. Proper insulation between metal components and cables is essential to avoid such problems. Mechanical damage during bending is another concern. Cables must be laid with adequate turning radii to prevent internal damage that might go undetected until a fault occurs. Ensuring proper handling and alignment of cable joints and terminations is critical for long-term performance. Moisture intrusion into joints and terminals is a common cause of low-voltage cable failures. Sealing these points effectively is vital to maintaining insulation integrity. Additionally, grounding the metal sheath of low-voltage cables is essential to prevent dangerous induced voltages and ensure safe operation. Overall, careful planning, proper installation, and regular maintenance are key to ensuring the reliability and longevity of power cable systems.
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