Normally underground power cable contain one or more conductor which covered with insulation which covered by protection insulation cover also.Most of underground cables are use for electric power distribution purposes under urban areas. But recent development of the cable industry made possible for transmit more high voltage levels so now these underground cables can also use for power transmission also.Normally in transmission system underground cables are use for short distances.
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Advantages of Underground Power Cable
Electric power can be transmitted or distributed either by overhead system or by underground electrical cables.Such locations may be thickly populated areas where municipal authorities prohibit overhead lines for reasons of safety, or around plants and substations or where maintenance conditions do not permit the use of overhead construction so we have to use underground cables in these occasions. The underground cables have several advantages such as:
1. Less liable to damage through storms or lightning
2. Low maintenance cost
3. Fewer chances of faults
4. Smaller voltage drop
5. Better general appearance
Underground Power Cables On their Service
Types of Underground Power Cable service may be classified in two ways according to;
1. The type of insulating material used in their manufacture
2. The voltage for which they are manufactured.
Underground Power Cable Classification According to Voltage Levels
However, the latter method of classification is generally preferred, according to which cables can be divided into the following groups:
1. Low-tension (L.T.) cables — up to 1000 V
2. High-tension (H.T.) cables — up to 11,000 V
3. Super-tension (S.T.) cables — from 22 kV to 33 kV
4. Extra high-tension (Fill cables — from 33 kV to 66 kV
5. Extra super voltage cables — beyond 132 kV
Underground Cable Classificaions According to Thir Core
A cable may have one or more than one core depending upon the type of service for which it is intended. It may be ;
Underground cable which are used is depending upon the
1. Operating voltage
2. Load demand.
3. Type of service
There are so many manufactures produces so many types of UG cables but there are somethings common with all of them.