Why is high voltage better for power transmission than high current?

[berlinpose2]

I've done some research and the following is what I understand of the topic. Please correct me if I'm wrong.

When power is transmitted, electricity is sent to a transformer, which increases the voltage and decreases the current according to the relationship S = IV. The reason for doing this is to minimize power losses along the transmission line, which is equal to RI2 . However, isn't power loss also equal to V2 /R, so having a large voltage would also cause a large power drop? Clearly there is a fault in my logic here because the power calculated with current and the power calculated with voltage would not be equal, so I am looking for an explanation of this. Thanks!

 

[crshears]

Using a technique I just learned, I guess that's I[sup]2[/sup]Z that's incorrect . . .

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[LionelHutz]

I[sup]2[/sup]Z is the apparent power in an AC circuit. IZ is the AC voltage drop across a circuit. I[sup]2[/sup]R is the power loss in an AC circuit.

 

[Fischstabchen]

Lionel,

You are overlooking the fact of how much vars plays a role in maintaining voltage. The voltage drop over an individual element may be I*Z but the amount of vars consumed by that segment is I^2*X. For that reason, in my opinion, when you double the voltage you reduced your real losses by 75% but you also strengthened the system by much more than a factor of two. Voltage profiles on high voltage systems are much more flat. Moving large amounts of power over any distance at a lower voltage would be a nightmare. You would need capacitor banks everywhere.

 

[LionelHutz]

I simply pointed out that "Actual losses, as in power lost as heat, are only due to resistances in the circuit." I[sup]2[/sup]R, not I[sup]2[/sup]Z. You can write an explanation of how the reactance and resistance of a high voltage line changes for the better if you want, but I fail to see how that changes the fact I posted about the heat losses being I[sup]2[/sup]R and not I[sup]2[/sup]Z.

 

[cuky2000]

The optimal transmission line voltage is a direct function of several factors such as the transmission line length, maximum power transmitted, the transmission network topology, desirable system reliability, operation losses, initial capital cost, among other factors.

The curve below provides a simplified illustration of how a higher transmission voltage improves the stability and power quality limit.

I hope this help