A three-phase transmission system requires what fraction of the total weight of conductor needed for a single or two-phase system?

In a three-phase transmission system, the conductor weight requirements differ from those of single or two-phase systems due to the way power is distributed and conducted. A three-phase system can transmit power more efficiently than a single-phase system because it uses three conductors carrying currents that are out of phase with one another. This phase displacement allows for more balanced loads and reduces the amount of conductor material needed.

To understand this better, if you consider a single-phase system requiring a certain weight of conductor, a two-phase system would typically require more conductor material due to the need for redundancy and balance between the two phases. However, when shifting to a three-phase system, the optimal distribution of electrical load allows for a reduction in the total conductor weight needed.

The three-phase system efficiently utilizes the power delivered through shared conductors, allowing it to require approximately three-quarters of the conductor weight needed for single-phase or two-phase systems. This efficiency is significant in minimizing overall material costs and structural load while maximizing electrical transmission effectiveness.

Thus, the correct answer accurately reflects the relationship between the conductor requirements of a three-phase system compared to single or two-phase systems, aligning with the principles of electrical transmission efficiency and load balancing, leading to the conclusion that a three-phase system needs