19 Difference between Overhead Lines and Underground Cables

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The power plant aka power station is a prominent source for electric power generation. The main function of the power plant is to transfer the generated electricity (i.e. power) to the industrial loads and consumers.

For this operation, we require a large network of conductors between the generating station and the consumers. This network is called as the Transmission system and Distribution system.

Transmission system and Distribution system

Both systems have different roles like-

  • The transmission system delivers the bulk power supply from the power station to the substation or to the industrial load.
  • The distribution system delivers the power supply from the substation to the consumer.

These two systems deliver AC or DC power in two different ways. One way is the overhead lines and another way is the underground cable.

In this tutorial, we will study what is the difference between overhead lines and underground cables.

Comparison between Overhead Lines and Underground Cables

#ContentOverhead LineUnderground Cable
01ConductorFor the overhead (transmission and distribution) lines, the bare conductor is used. For underground (transmission and distribution) cable, the insulated conductor is used.
02Conductor
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.
03Electric 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.
04Voltage
Capacity
It carries a high voltage (near about the 400kV).It carries a limited voltage (not more than 66kV).
05LookYou can easily visualize it.As these cables are underground you can not visualize them.
06InterferenceOverhead lines interfere with communication lines.Underground cable does not interfere with communication lines.
07Insulation
(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).
08Outage
Operation
It requires low maintenance to identify the outage location.It requires high maintenance to identify the outage location.
09CostThe overhead line is cheaper. The underground cable is expensive.
10JointUsers can easily join the extra connection on overhead lines. Users can not easily join the extra connection in underground cables.
11Fault Very easy to repair and clear the fault.Very difficult to repair and clear the fault.
12Proximity
Effect
The proximity effect does not affect overhead lines. The proximity effect affects the underground cables.
13Corona
Effect
Corona effect finds in the overhead system. Corona effect does not find in the underground system.
14Environmental
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.
15Maintenance
The maintenance cost of the overhead system is high.The maintenance cost of the underground system is low.
16Reliability
The overhead system provides low reliability. The underground system provides high reliability.
17ExplosionIt increases the risk of fire or explosion.It decreases the risk of fire or explosion.
18Safety
(for the human being)
This system or lines are not much safer.This system or cables are much safer.
19Flexibility
(for conductor)
High flexibility finds in the layout of the overhead power circuit.Less flexibility finds in the layout of the underground power circuit.

This is all about the basic specifications of underground cables versus overhead lines. These specifications also describe the advantages and disadvantages of overhead power lines and underground cables.

If you have any queries regarding the comparison between overhead transmission lines and underground cables, drop your comment below.

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