Meaning and mechanism
The transmission lines exhibit resistance, and as current flows through them, the energy is converted into heat. The power supplied by the power plant and the power consumed by the load may differ by the amount of loss.
Maintaining a constant power P=VI, while doubling the voltage, results in a current that is half. The I²R losses on the same circuit line are reduced to a quarter.
Relationships and conditions
The experiment utilizes a predetermined transmission input power, employing I=Pin/Vsend and Ploss=I²Rline. The resistance is defined by its material, length, and cross-sectional area.
The modeled input power for transmission lines differs from the output power for distribution lines that have been adjusted. In actual AC systems, there are influences from apparent power, insulation, and transformers, as well as distribution lines.
What to observe in the simulation
At fixed transmission input power, raising voltage reduces I²R losses.
Distributed effects and AC reactive power are omitted. This differs from a constant received-power model. In the invalid transmission region, do not interpret line heating as an actual loss. Experiment on screen; do not reproduce this with real power supplies, outlets or high voltage.
Key relationships and symbols
I = Pin/Vsend · Rline = ρL/A · Ploss = I²Rline
| Symbol | Meaning | Unit |
|---|---|---|
| Pin | Transmission input power | W |
| Rline | Line resistance | Ω |
| Ploss | Resistive line loss | W |
Worked example
For the same input power and line, what does a 33.6 W loss become when voltage rises from 1000 V to 2000 V?
8.4 W
Common misconceptions
- The reduction in losses in high-voltage transmission is not because the voltage itself eliminates resistance, but because the same amount of power results in a smaller current.