# Homework Help: HVDC Article Discussion

1. Jan 8, 2013

### jegues

Hello all,

I've been encourage by my professor to participate in an open discussion regarding the article I've attached to this post. See below for link!

The article is quite dated as it is from IEEE SPECTRUM June 1985, but it is nonetheless still useful.

As a brief summary of the article I've found that it discusses the following main points,

• Economics: HVDC systems can transport more power over longer distances than AC lines of equivalent costs.
• Immunities: DC transmission is inherently immune to inductive reactance problems found in long distance/large load AC transmission. DC cables can also carry more power than AC cables of the same size, with less losses.(for cables > 70km) DC lines costs 2/3rds as much in comparison to AC lines, but required added conversion equipment at either end of the DC line
• In comparison to AC: HVDC transmission can link neighboring asynchronous networks economically and reliably. Furthermore, DC lines can transmit any level of power asynchronously between networks.
• Health Concerns: There is concern that HVDC may have harmful health effects on people living or working near the line. Limited scientific investigation of HVDC lines has not found the static electric and magnetic fields are any more dangerous the AC transmission lines. However, air-ion levels are much higher near HVDC lines and are the primary source of concern over the possible harmful health effects.
• Trade Issues: The utilities would pay between 60-80% of what the cost would be for electricity generated by fossil fuels.
• Technology Advances: New specialized HVDC circuit breakers will ensure that larger, multiple terminal HVDC systems can be constructed, as opposed to single point to point transmission.
• Other: HVDC systems allow the expansion of back-to-back ties, allowing utilities in different transmission networks to exchange energy to maximize economical usage.

Please take a read of the article and let me know what you think. Is there any key points I did not highlight? Feel encourage to share you thoughts/opinions!

Cheers!

2. Jan 8, 2013

### jim hardy

The article refused to load for me.

My initial reactions:
1.
That equipment is dreadfully complex. In the early days of HVDC it caused interactions with steam turbine shafts and fractured some (that's a disaster) - look up "sub-synchronous resonance". Presumably it's been conquered by now...

2.
?? that sounds situation specific.

3. Anything that sounds too good to be true usually is.

But it's great in a country like Japan where one half is 50 hz and the other half is 60 hz.

keep in mind i wasnt able to read your article. But prepare yourself to defend that kind of thinking from old guys like me..

old jim

3. Jan 8, 2013

### AlephZero

I'ts probably been understood a bit better than it was back then. But "understood" $\ne$ "conquered".

FWIW I spent about 10 years (not full time!) trying to figurie out why one of our products "made a funny noise" (apparently nothing dangerous, but loud enough to frighten people) when operated by one of our customers, but not be any of the others.

The cause turned out to be ..... sub-synchronous resonance....

4. Jan 9, 2013

### CWatters

5. Jan 10, 2013

### Staff: Mentor

@jegues -- I'm not understanding the higher E field under the DC power lines. Do you understand why it's higher?

From the article:

500kV AC power lines --> 9kV/m

+/-400kV DC power lines --> 30kV/m