The role of insulation in underground power cables is to prevent the flow of electricity from the cable to the surrounding environment and vice versa. The proper operation of a cable relies on the type of insulation used for cables. The insulation material used in cables should possess the following features:
- Economical: The cables used should be low-cost so as to make the underground system an attractive choice for individuals and organizations
- Flexible: The material used for cables should be flexible enough to bend and conform to the shape of the cable without cracking or breaking.
- High dielectric strength: High dielectric current ensures that electrical breakdown of the cable is avoided
- High insulation resistance: The insulation resistance of the cable should be high to avoid leakage current
- High mechanical strength: It ensures that cables can withstand the mechanical stress experienced during handling, installation or laying of cables
- Non-hygroscopic: The term non-hygroscopic refers to the material that does not absorb moisture from the air or its surroundings. Insulation materials used for cables is not supposed to absorb moisture from air or soil. Since the moisture content decrease the insulation resistance and accelerates the breakdown process in cables
- Non-inflammable: It is desired that materials used for insulating cables should not ignite or burn in the presence of heat, sparks, or flames.
- Unaffected by acids and alkalis: When insulation comes in contact with acids or alkalis Chemical degradation, Hydrolysis, and discoloration might occur. The impact of acids and alkalis can’t be totally neglected, however, the application of an appropriate grade of PVC that is resistant to chemical attack ensures the longer operations of cables.
- Water resistance: If water comes in contact with an electrical conductor, it might lead to electrical shock, electrocution, a short circuit with equipment or even fire. There are many instances when or accidents where water might come in contact with electrical cables. In order to prevent these hazards or to reduce the impact of these hazards, the insulation material used for cables should be water resistant.