In mine power supply systems, high-voltage lines typically use armored cables, which have a significantly lower failure rate compared to low-voltage cables. However, the power supply in mining areas is often considered a weak point in the system due to harsh working conditions. As a result, the selection of cable type and cross-section plays a critical role in ensuring the safety and reliability of the power supply. This article outlines key considerations for selecting appropriate cables and determining their cross-sectional dimensions.
When choosing a cable model, it's essential to consider factors such as power supply reliability, safety, and economic efficiency. According to Article 467 of the Coal Mine Safety Regulations, the following guidelines must be followed:
1. The actual laying location of the cable must be compatible with its allowable level difference.
2. Cables should have conductors of sufficient cross-section to ensure proper earthing and protection.
3. Aluminum-coated cables are strictly prohibited.
4. Flame-retardant cables that have passed inspection and obtained the required safety certification for coal mine products must be used.
5. The main core section of the cable must meet the load requirements of the power line.
6. For fixed high-voltage cable installation:
- In shafts or inclined tunnels with angles over 45°, PVC-insulated heavy steel wire armored cables with PVC sheathing or cross-linked polyethylene insulated thick steel wire armored cables with PVC sheathing should be used.
- In horizontal tunnels or shafts with inclinations of 45° or less, PVC-insulated steel strip or thin steel wire armored cables with PVC sheathing, or cross-linked polyethylene insulated steel strip or fine steel wire armored cables with PVC sheathing should be used.
- Aluminum-core cables may be used between inclined shafts in intake areas, underground depots, and central substations, but copper-core cables are required elsewhere.
- Fixed low-voltage cables should be M-type or non-armored cables, or mobile rubber-sheathed cables of the corresponding voltage class.
- Non-fixed high- and low-voltage cables must use rubber cables that meet the Mr818 standard. Mobile and handheld electrical equipment should use dedicated rubber-sheathed cables.
- Cables for lighting, communication, signaling, and control should use armored communication cables, rubber-sheathed cables, or plastic cables of the M, factory, or factory type.
- Aluminum cores are not allowed in low-voltage cables, especially in mining areas where they are strictly prohibited.
**Cable Cross-Section Selection**
The selection of cable cross-section involves both high-voltage and low-voltage cable sizing, with low-voltage cables being the primary focus. When choosing the main core size for low-voltage cables, several important principles must be followed, especially in long mining area power supply lines:
1. The actual temperature rise of the cable during normal operation should not exceed the maximum allowable temperature for its insulation.
2. Voltage loss along the cable line must be within acceptable limits.
3. The cross-section must meet mechanical strength requirements to prevent damage under operational conditions.
Mine cables are specifically designed for use in coal mining environments, including ground-based equipment and downhole wiring. They cover a wide range of applications, from mining machines and transport systems to communication, lighting, and signaling devices, as well as drill cables, cap lamp wires, and power cables for mobile substation installations. Proper cable selection is vital for maintaining safe and efficient operations in such challenging environments.
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