There are two methods of providing the electric power from the generating station to the consumers and they are:
i) By bare overhead lines.
ii) By underground cables.
Now both of this lines have some advantage over the another and some disadvantages also. When it comes to the comparison of these two type of cables, some point can be easily highlighted:
For overhead transmission lines inductance effect is prominent but for underground cables capacitance effect is more prominent.
Overhead transmission lines are less costly than the underground transmission line, because the conductors of overhead lines do not have any insulation around them, so that the dissipation of heat is better as well as this line is economical too. This is the main reason for same transmission of power, the size of the conductors for overhead lines are smaller than those of the underground cables, which eventually effects the costing.
The main difference of costing is due to the use of the insulation types. The overhead line insulators are typically made of porcelain. The air surrounding the overhead lines provides insulation also. But for underground cables, the insulation is provided by wrapping each conductor by high grade paper tapes. And metal sheet is also applied to prevent moisture. For oil filled cables, oil reserves are situated at certain distances to keep the oil pressure intact. These developments makes the insulation process much complex and expensive.
Again the cost for installing the overhead transmission tower is lower than installing underground cables.
But underground cables provide more safety to the public and help the city or area looking clean and less congested.