AC versus DC power transmission (2 - Electricity Distribution)

Why is AC used more often than DC? And why are power lines usually at high voltages? Here I explain the history of alternating and direct current and work an example showing how high voltage transmission is more efficient in terms of line losses. Then I relate this to the use of AC for electricity distribution.

Full edX course with interspersed practice problems to help you learn:

Aaron Danner is a professor in the Department of Electrical and Computer Engineering at the National University of Singapore.

Video filmed and edited by Cheryl Lim.
@randomcheryl

[comeflywithme]

concise and useful in clear and beautiful English. what a pleasure to watch your lectures.

[ohgoditsjames]

DC transmission is common on long feeders and at grid interconnections. DC transmission is more efficient when the circuits are very long (500km+) and at ultra high voltages (above 500kV) because of the high inductance and capacitance that AC transmission lines have and because of the skin effect. You also only need 2 cables instead of 3, saving on conductor material. The up front cost for the converter stations is the biggest hurdle, which is why they're more economical above a certain circuit length.

[chrisaxelos]

greatly explained the energy loss part and why we need transformers ( high voltage on long distances and low voltage where energy consumption takes place)

[Julliver]

Very nice, concise and clear course on Edx, Thank you

[comeflywithme]

beautifully explained. what a gifted lecturer!

[tdc]

I calculate the low voltage load resistance to be 53 ohm and 4.3 amps for 230v and 1kW. How are you calculating for this example? Resistance =Voltage^2 / Power is what I used.

[ThePaddyMak]

What if the load for the both voltage sources is the same i.e 10 ohms. Surely the load is not fixed

[strengthwisdom]

Hello sir, I have a question.
Since the energy that goes through the wire is the same, regardless of the voltage, what is the fundamental change that causes the energy loss. What I can imagine is that with the low voltage we have current through the wire and with the high voltage we have current to the perimeter and around the wire.
Can you please give your explanation?
Thank you

[ilcantastorie]

Why are long submarine cable DC and not AC?

[borysmaysza]

If we have U=230V and P(load)=1000W then R(load)=Upower2/P=53Ohm, not 10Ohm. Then P(line)=157W, not 1300W. Am I right?

[abcdef]

at 4:29 P =I^2 * R (V=I * R) = V^2/ R
P100 = (100v)^2 /2 ohm
P200 = (200v)^2 /2 ohm
P200 >> P100 whats wrong in this way

[binaryglitch]

I'm still getting Leyden jar deliveries from the milk man, er I mean elecrticity man.

(That's a joke, I'm a licensed and certified electrician... I say I'm an electrician not to imply that I'm too knowledgeable about electricity to believe in the Leyden jar delivery man... just to imply that I can't pass up an electricity joke.)

[rigobertocantuna]

incredible that it does not mention Nikola Tesla.

[NovemberCharlieNC]

in the DC Transmission, you made calculations to show that low voltage has a bigger power loss than high voltage. The problem with what you just showed is that you put in the RLoad yourself. I could make a video, wit the same calculations and say oh we're using RLoad to be 1k Ohms in low voltage and RLoad to be 1k ohms as well on high voltage. It just makes no sense.

[oldfartrick]

And once again Tesla is ignored as the other inventor.