(introduction...)

Consumers’ installations in the low-voltage range are very frequently connected to the power supply networks by underground cables. In this, the traditional paper-insulated compound-impregnated cable is more and more replaced by plastic-insulated dry cable.

At almost the same current-carrying capacity several advantages are offered by plastic-insulated underground cables as compared to compound-impregnated cables:

- omission of the expensive lead sheathing,
- the insulation value will not be reduced due to loss of compound.
- considerably lower weight.
- simpler preparation,
- no problems in overcoming differences in height.

Fig. 3.1. Plastic sheathed cable with copper conductor

1 copper conductor, 2 plastic insulation, 3 common conductor covering, 4 armouring of steel strip, plastic sheath

The concentric conductor of the plastic cable in fig. 3.2. may be used as centre conductor or protective conductor.

Fig. 3.2. Plastic cable with solid aluminium conductors

1 aluminium conductors, 2 plastic insulation. 3 common conductor cover, 4 concentric conductor of aluminium flat wires (armouring), 5 protection against corrosion, 6 plastic sheath

In lieu of the conductor material copper, becoming ever more expensive and scarcer, more and more underground cable the conductor material of which consists of aluminium is being applied.