Unit-3 - PS-I.pdf
- 11. Compression Test
- 14. Chemical Test
- 68. # Content Overhead Line Underground Cable 01 Conductor For the overhead (transmission and distribution) lines, the bare conductor is used. For underground (transmission and distribution) cable, the insulated conductor is used. 02 Conductor Size The size of the conductor is smaller as compared to the conductor of the overhead cables. The size of the conductor is large due to the coated insulation. 03 Electric Current Capacity The overhead line has a higher current carrying capacity than the underground cable. The underground cable has a lesser current carrying capacity as compared to an overhead line. 04 Voltage Capacity It carries a high voltage (near about the 400kV). It carries a limited voltage (not more than 66kV). 05 Look You can easily visualize it. As these cables are underground you can not visualize them.
- 69. 06 Interference Overhead lines interfere with communication lines . Underground cable does not interfere with communication lines. 07 Insulation (Types of Insulations use) It requires less insulation (only at the contact point of the tower). It requires more insulation (for coating the whole conductor). 08 Outage Operation It requires low maintenance to identify the outage location. It requires high maintenance to identify the outage location. 09 Cost The overhead line is cheaper. The underground cable is expensive. 10 Joint Users can easily join the extra connection on overhead lines. Users can not easily join the extra connection in underground cables.
- 70. 11 Fault Very easy to repair and clear the fault. Very difficult to repair and clear the fault. 12 Proximity Effect The proximity effect does not affect overhead lines. The proximity effect affects the underground cables. 13 Corona Effect Corona effect finds in the overhead system. Corona effect does not find in the underground system. 14 Environmental Impact It gets impacted by the occurrences of environmental attacks (like lightning, windstorm, thunderstorm). There are fewer chances of environmental attacks in an underground system. 15 Maintenance The maintenance cost of the overhead system is high. The maintenance cost of the underground system is low.
- 71. 16 Reliability The overhead system provides low reliability. The underground system provides high reliability. 17 Explosion It increases the risk of fire or explosion. It decreases the risk of fire or explosion. 18 Safety (for the human being) This system or lines are not much safer. This system or cables are much safer. 19 Flexibility (for conductor) High flexibility finds in the layout of the overhead power circuit. Less flexibility finds in the layout of the underground power circuit.