Hi I was not completely aware that High Voltage DC Transmission Systems are replacing HV AC transmissions systems throughout the world. There's some very cool engineering going on. HVDC headends look straight out of Buck Rogers:
Yes but for a long time (still do) wonder about X-rays from any arc or leakage. Those are voltages X-ray machines work. Still, I'm thinking about a portable, DC charger. Both my Tesla and BMW i3 are limited to 30-32 A, 240 VDC, or about 7.2 kW by the built-in AC-to-DC charger. So I've been thinking about a high-efficiency, buck switching supply that can handle 40 A, 240 VDC. In theory, it should charge my Tesla at 9.6 kW and with a Tesla-to-CCS-1 plug adapter, the BMW too. A well designed, high efficiency buck regulator should have 95-97% efficiency with the waste going to heat. So a worst case, 5% loss, should have a maximum, 50 W of waste heat which a metal case with 'standoff fins' should easily handle without a fan. For good measure, the control electronics would measure the case temperature and derate it while lighting a high temperature LED. A water proof case, the operator can cool it off by whatever means available. Bob Wilson
In a car forum, maybe a better title would be something like "HVDC for electrical power transmission in the grid" or something like that, so a car-oriented reader isn't going "transmission? huh? oh THAT kinda transmission."
I don't understand why they are going to DC for long distance transmission. Traditionally DC is good for short distances and AC for long. What's changed?
I think it was more like high voltage is good for long distances, and AC is handy if you want high transmission voltages, because transformers are easy to build to step voltages up and down, but they only work for AC. But nowadays, DC/DC converters (like the one under your hood!) are established technology, making it possible to do high transmission voltages without having to go through transformers and AC.
A typical AC supply has a sine-wave shaped voltage profile with a peak of ~1.414 larger than the root mean square (RMS) voltage. The insulators have to handle this peak voltage a fraction of each cycle. But the rest of the time, the voltage is much lower. By using high voltage DC, you can in theory achieve a 141% increase in power for the same current over the same conductors. Bob Wilson
