5 ms·

High voltage DC? What's that about?

• Sanddancer 12y ago
  High voltage DC is actually cheaper and easier to do for long distances than AC. HVDC cables can be made cheaper because you don't have to worry about skin effect [1], and additionally, you don't have to worry about what phase each electrical system uses, nor the natural phase drift of electrical systems. It's why the west coast of the US uses HVDC for one of the paths of the Pacific Intertie. [1] http://en.wikipedia.org/wiki/Skin_effect http://en.wikipedia.org/wiki/Skin_effect
• tlb 12y ago
  It's more efficient for very long distance transmission. With AC transmission at 60 Hz, the wavelength is 5000 km. Things get complicated when you approach that distance. Also, with maximum peak voltage limited by arcing, DC uses the wires more efficiently because it's constantly at peak voltage, rather than oscillating up to it. Also, AC current creates a varying magnetic field that pushes the current flow away from the center of the wire, so only the outer region gets used, increasing resistive losses. It's not a huge effect at 60 Hz, but it makes some difference. https://en.wikipedia.org/wiki/High-voltage_direct_current https://en.wikipedia.org/wiki/High-voltage_direct_current
  • amaterasu 12y ago
    But, the switching/control equipment is substantially more complicated, voltage conversion is hard due to transformers not working at DC, and you still need to suffer inverter inefficiencies to convert things to AC for domestic use.
    • tlb 12y ago
      Right, so it only makes sense for very long distances where the cost & losses in the inverters are less than the losses from AC transmission.
  • subleq 12y ago
    What happens when the transmission distance approaches the wavelength?
• deleted 12y ago
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