Underground vs Overhead Electrical Cable

Electrical power transmission, which can be defined as transport of generator-produced electric energy to loads- is conducted through different types of electrical cables. Electricity generating stations and load consumption centers are connected to each other by a network of power transmission lines, mostly overhead cable lines. Power distribution system carries electricity from the local substation to individual households and other official as well as industrial establishments using both overhead and underground cable lines. This article deals with the debate about underground v/s overhead electrical cable. It is an attempt to compare both the types of electrical cable lines to understand their pros and cons.

Cost of Underground and Overhead Electrical Cable
Although many low voltage, local electric distribution lines are buried underground, almost all high-voltage electric transmission lines are tried to be placed as overhead cables due to the cost difference. Installation costs for underground cable transmission lines can be as much as 2.5-10 times the cost of an overhead cable line based on voltage. Overhead power lines are in fact, considered the most affordable industry standard due to many reasons. For example, the impact of cost of underground construction in some regions extend beyond the project area and the citizens outside the project area also stand responsible for such cost because of local laws. Therefore, underground cables are mostly not a preferred option considering electricity bills for all consumers unless safety is an issue. The repair cost of underground power cables too are higher than overhead cables.

Installation of Underground and Overhead Electrical Cable
Cost of installing underground cable is much higher than that of overhead cable and this is because its installation too is a tricky and challenging job apart from the fact that it can provide enough electricity to power whole cities and is technically complex and material intensive. The design and installation as well as maintenance costs for underground lines depend upon many factors which are mostly site-specific. Some of the factors involved in installation of underground cable include:

Time Needed for Underground and Overhead Electrical Cable Repair
There is one more reason for not giving preference to underground cables as transmission lines- the additional time it needs for repairs. It takes more time to locate, diagnose the problem and repair an underground transmission line. While an overhead cable can be repaired in hours or days, it may take weeks or even months to repair an underground cable.

Operational Challenges of Underground and Overhead Electrical Cable
Overhead cables are also preferred due to the comparatively lower rate of operational challenges involved. It is a known fact that all electric lines produce heat and therefore have a limit on the amount of power that they can carry. Underground cables cannot dissipate heat as efficiently as overhead lines can do. This is due to many factors like type of surrounding soil, adjacent underground utilities, depth of installation etc.

Underground vs Overhead Electrical Cable- The Conclusion
From the above discussion, it seems that overhead electrical cables are more beneficial than the underground cables due to many concerns like cost, time and level of challenge involved in installation and repair of underground cables etc. However, there are many conditions when it becomes necessary to lay cables underground like if there is no viable overhead corridor, such as in densely populated areas or near airports. Even in such situations, specific construction measures are essential for safe and reliable operation of the cable line.