4 ms·
DC works for transmission because it operates at incredibly high voltages. Power is voltage * current, but resistive losses are proportional to current only. S
by floatrock 9y ago
DC works for transmission because it operates at incredibly high voltages. Power is voltage * current, but resistive losses are proportional to current only. So the theory that makes it work is since P=I*V, energize the line at incredibly high voltages and get very little actual current flowing to minimize resistive losses for a given power rating. UHVDC is something like 800kV.
DC is much less workable at low voltages like 12v or 5v common in household application -- the P=IV equation is more dominated by current, so with more current the resistive losses add up quickly even in a run across your house (it'll be down to 10 or 8v by the time the wire reaches the far end of your house). Not to say some people haven't suggested wiring homes with 12v lines... data centers have implemented (or at least experimented with) DC distribution due to the density of DC devices.
- marshray 9y agoThat's all true for AC as well though.
- MertsA 9y agoThe benefit of HVDC transmission lines is that you don't have the skin effect at all which makes a difference even at 60 Hz when the cable is as thick as your arm. If you've ever seen one of those large transmission lines where each phase has three conductors all very close to each other but kept slightly apart that's done because of the skin effect. Also there's always capacitance which will cause some loss for AC but of course capacitance won't affect a DC transmission line. HVDC also makes combining different electrical grids extremely simple as there's no phase difference or frequency difference to worry about. DC also requires lower peak voltages as AC is going to be sqrt(2) times higher than the rms voltage.