Robert Bruninga via EV wrote:
I can see that my original statement was confusing. What I meant was that for the same conductor and same I^2R loss, DC can deliver nearly 40% more power because the DC line can operate at the PEAK voltage rating of the line, whereas the AC line only delivers that same current power at RMS voltage, not peak. 40% increase is worth doing for long point-to-point transmission (with no taps)
It's not that simple. Insulators have different voltage withstand capabilities on AC or DC. You can't easily compare them.
One example: DC always has the same polarity, so leakage currents through the insulation cause corrosion and electrodeposition effects. This lowers the maximum voltage that an insulation can withstand on DC.
Another example: If there's an arc, it self-extinguishes on AC at the next zero-crossing. On DC, the arc will *continue* until some external device interrupts the flow of current.
Another example: On AC, corona is more likely to occur. The higher the frequency, the worse it gets.
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