Polythene

What is polythene? It is thermoplastic material used as insulator, and for many other purposes in communication industry. Polythene is mostly used in cases where a chemically-resistant plastic material is needed.

It is a well-known fact that cables are classified as belonging to the main parts in the modern communication systems. Cables used for communica­tion purposes differ in length, construction, properties, and, naturally, in their cost. Polythene cables belong to the type of cables widely used in trans­mitting electrical energy from area to area, since polythene is the popular and highly useful insulating material of today.

Polythene cables are comparatively new devices. Their industrial pro­duction started only after World War II. Since that period they have been widely used in different spheres of energy transmission throughout the world.

Polythene cables are known to have a number of advantages: they may be used for both a conductor insulation and a sheath, which makes them one of the most usable substance in industry. There exist two main types of poly­thene cables: the one having polythene insulation for the conductors, and the other having paper insulation. To these belong lead-sheathed paper-core cables. The number of pairs in different cables is also different. Of them the cables including 100 pairs and more have natural polythene sheaths.

Unlike lead-covered cables, polythene ones can be laid directly in the ground without ducts since they are corrosion-proof, while lead-sheathed cables are usually laid in asbestos-cement ducts since they can be easily cor­roded. Another advantage of polythene cables is that they can be used in much longer length than lead-covered ones.

The process of laying cables is known as "long-length cabling".

Ответьте на вопросы по тексту

• What is polythene?

• What do cables differ in?

• What are the advantages of polythene cables compared with lead-sheathed ones?

• Why can polythene cables be laid directly in the ground?