4/16/2023 0 Comments Long forgotten fields dvFor this reason, it's called self-inductance, and the self-inductance of a long transmission cable is really significant. It isn't - a coil of wire halfway between here and the Magellanic Cloud will have precisely the same reactance and cause precisely the same electrical effects sat on your desk. A common misconception (repeated by Olin) is that this is due to transferring power to things around it. This creates reactance for AC power transmission. The losses for AC primarily come down to the inductance of the cable. I'll try not to repeat too much of his answer, but I'll clear up a few things. Olin Lathrop's answer is partially right, but not quite. I actually worked on HVDC schemes, back in the mid-to-late 90s. Synchronization was also a factor in using DC. The expense of building and operating this plant is worth it due to the significant power savings of transmitting DC instead of AC. This plant converts that to AC and dumps the power onto a large regional AC transmission line in Ayer Massachusetts at 42.5702N 71.5242W. Here is a example of what it takes to convert high voltage DC back to AC:ĭC power from large dams in Quebec enters at top right. That expense is only worth it if the transmission distance is long enough so that the efficiency savings outweigh the cost of the DC-AC conversion plant over its lifetime. It takes a large plant to do this, which means significant expense. Converting DC back to AC to dump it onto the local grid at the receiving end is not a trivial process. The flip side is that AC is easier to convert between voltages. This gets tricky when the distances are large enough to be significant fractions of a cycle. Two AC grids need to be phase-synced to be connected together. With DC current, the magnetic field doesn't change and therefore doesn't transfer power.Īnother advantage of DC is that it doesn't require synchronization between grids. In effect, the transmission line is the primary of a transformer, and conductors near it are secondaries. The changing magnetic field around a wire carrying AC current causes induced voltage and current in nearby conductors. Long transmission lines act as antennas and do radiate some power. However, the power transmitted is the current times the RMS, not peak, voltage. With DC, the RMS and peak voltages are the same. With AC, that is 1.4 times higher than the RMS. The lines have to withstand the peak voltage. Higher voltage allowed with DC for the same transmission lines.It is more efficient to transmit DC using about the same infrastructure.
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