The insulating material for a cable should have

Q. The insulating material for a cable should have

1. Low cost
2. High dielectric strength
3. High mechanical strength
4. All of the above

Answer: All of the above

Insulating Materials for Power Cables

• An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field.
• It is often called a dielectric in radio frequency cables.
• In general, the insulating materials used in cables should have the following properties :

1. High insulation resistance to avoid leakage current.
2. High dielectric strength to avoid electrical breakdown of the cable.
3. High mechanical strength to withstand the mechanical handling of cables.
4. Non-hygroscopic i.e., it should not absorb moisture from air or soil. The moisture tends to decrease the insulation resistance and hastens the breakdown of the cable. In case the insulating material is hygroscopic, it must be enclosed in a waterproof covering like lead sheath.
5. Non-inflammable.
6. Low cost so as to make the underground system a viable proposition.
7. Unaffected by acids and alkalies to avoid any chemical action