Generally, the cable installation depends on the types of cable to be used and installation conditions. Here we will discuss the types of cable installation. There are two modes of installing a cable:
- Underground cable installation
- Overhead cable installation
Here we will discuss the underground installation of the cable.
Underground Cable Installation
For installing an underground cable, we use armored cables to prevent mechanical accidents before laying cables under the ground. Also, we must survey the cable routes. The cable to be underground should have the following properties:
- The moisture of soil should not enter the core of the cable.
- It must have high insulation resistance.
- It should be able to withstand the heat produced due to the flow of current.
Installing of the underground cables has following types:
- Direct laying system
- Drawing system
- Solid system
Direct Laying System of Cable Installation
This method requires digging a cable trench of about 1.5 m deep and 45 cm wide. Then a layer of fine sand about 10 cm thickness covers the trench works. Then the cable is laid over this sandy bay. The sand prevents the entry of moisture from the ground and thus protects the cable from insulation breakdown.
After laying the cables, another layer of sand of about 10 cm or a concrete block covers the cable. Here we will cover the trench works with bricks to provide additional protection to the cable. For laying more than one cable on the same trench, we provide a horizontal or vertical interaxial spacing of at least 30 cm to reduce the effect of mutual heating and also to ensure that a fault occurring on one cable does not damage the adjacent cable.
This method of installing the cables requires laying of conduit or duct of glazed stone, cast iron, or concrete in the ground with manholes at a suitable position along the cable route. The cables are pulled into positions from respective manholes.
In this system, the cable is laid into the trough of cast iron or stoneware asphalt, or treated wood. When the cable is laid into the position the trough is filled with bituminous asphalt compound and then covered over the cable to be laid. A lead cover as a trough provides good mechanical support.