Introduction

Introduction

The transmission and distribution of an electrical power can be with the help of overhead transmission lines or by underground cables. It has been mentioned that in thickly populated areas like towns and cities, the use of overhead lines is not practicable. In such cases electrical energy is transmitted and distributed with the help of underground cables. In its basic form, an underground cable is a conductor provided with proper insulation. As the voltage level increases, the cost of the insulation increases rapidly and thus the use of underground cables is restricted to low and medium voltage distribution.

1. Advantages of Underground Cables

Compared to overhead lines, the underground cables have the following advantages,

1. It ensures non-interrupted continuity of supply. The possible supply interruptions due to lighting, storms and other weather conditions are eliminated because of underground cables.

2. It requires less maintenance.

3. The accidents caused due to breakage of overhead line conductors are eliminated due to use of underground cables.

4. The voltage drop in the underground cables is less.

5. The life of underground cables is long compared to overhead lines.

6. The beauty of cities and towns get maintained due to underground network of cables.

7. The overhead lines use bare conductors which is unsafe in thickly populated areas. Hence from safety point of view, the underground cables are more advantageous.

The only drawbacks of the underground cables are the extremely high initial cost and insulation problems at high voltages. In India, the big cities have adopted the system of underground cables for the transmission and distribution.

Thus the use of underground cables is mainly for the distribution of an electrical power at low and medium voltages. Its use is almost compulsory at the locations where use of overhead lines is not practicable due to the safety reasons such as congested urban areas, crossing of wide roads, near gas plants and refineries, near substations etc.

Review Question

1. What are the advantages of underground cables over overhead lines?

AU : May-12, Marks 10