What are the advantages and disadvantages of dc transmission system?

The advantage and disadvantages of the D.C. transmission system.
 
Advantages.

1. It needs only two conductors as compared to three for a.c. transmission.
2. There is no inductance, capacitance, phase displacement and surge problems in d.c. transmission.
3. Due to the lack of inductance, the voltage drop in a d.c. transmission line is smaller than the a.c. line for the same load and sending end voltage. For this reason, a d.c. transmission line has better voltage regulation.
4. There is no skin effect in a d.c. system. Hence, the entire cross-section of the line conductor is utilized.
5. For the same working voltage, the potential stress on the insulation is smaller in the case of d.c. system than that an a.c. system. Therefore, a d.c. line needs less insulation.
6. A d.c. line has smaller corona loss and decreased interference with communication circuits.
7. The high voltage d.c. transmission is free from the dielectric losses, particularly in the case of cables.
8. In d.c. transmission, there are no stability problems and synchronizing difficulties.

Disadvantages

1. Electric power cannot be generated at large d.c. voltage due to commutation problems.
2. The d.c. voltage cannot be stepped up for transmission of power at large voltages.
3. The d.c. switches and circuit breakers have their own limitations.