Underground cable installation is a highly technical task that requires skillful execution and adherence to standard procedures. The process itself is lengthy, requiring multiples steps. This article is an overview of the procedure, methods, and tips when laying underground cables.
Stages in Underground Cable Installation
- Preparation of the site, cable, and equipment
- Laying of the cables underground
- Removal of cable insulation layers
- Fixing cable joints and terminals
- Stamping conductor connections
- Cables testing
When the direct laying method is used, the process involves digging trenches underground and embedding the cabled within layers of sand, each at 10cm deep. This is the cheapest way to lay underground cables.
The draw-in method is more costly than direct laying but minimizes future repair costs. The cables are cast in iron, glazed stone, or concrete. They are then provided with manholes for access, making them the most suitable method for urban areas.
In solid system method, the cables are also laid and covered trenches like the indirect method. The difference is that the cables are protected from mechanical elements through open pipes or troughs. A solid system is no longer commonly employed because it is labor intensive and less cost-effective than the two other methods.
Important Pointers for Underground Cable Installation
Never carry or drag the cables over uneven surfaces
Carrying the cables over the shoulders or dragging them on the ground could push the lines beyond their minimum bending radius. This could result in ruptured cables and insulations. In which case, the lines become faulty even before they are put to use.
Minimum bending radius is measured based on the external diameter of the cable. While they are being laid, lead-sheathed cables have a minimum radius of 20 da – that is, 20 times the external diameter. Aluminum sheathed cables are more delicate and can’t be bent to less than 25 da. Plastic sheathed cables, on the other hand, are more flexible with around 15 da.
Be wary of temperature drops
Cables are susceptible to environmental factors. When the temperature outside drops below 10°C, they become brittle and prone to damage. At 4°C, it’s no longer advisable to do the installation at all. In an emergency or urgent cases, experienced underground cable professionals commonly warm the cables using heater fans to retain cable integrity while working under extreme conditions
Do not skimp on the proper equipment
Badly laid out systems result in more faults and higher maintenance, so it’s important to get things right the first time. Mechanical devices like winches, cable drums, angular idlers, and cable stampers lessen the margin of error during installation. These also hasten the work pace and ease the grunt work for the team on site.
Proper installation of underground cables has a substantial impact on the serviceable life of a utility system, whether simple or complex. Understanding the process and implementing precautions can be guarantee longer useful life and less taxing upkeep for your underground channels.