It takes strong and determined population to build a lasting civilization. If the civilization includes electricity and the inhabitants live in a hilly place with an often-unforgiving climate, the required strength and determination increases proportionally. Such is the case of the gentlemen who strung up the first half-million VDC transmission line across New Zealand, connecting the country’s two main islands.
Construction for the line known as the HVDC Inter-Island link began in 1961. It starts at the Benmore hydroelectric plant on the south island and runs north to Cook Strait via overhead cables. Then it travels 40km underwater to the north island and ends near Wellington. This is the kind of infrastructure project that required smaller, preliminary infrastructure projects. Hundreds of miles of New Zealand countryside had to be surveyed before breaking ground for the first tower support hole. In order to transport the materials and maintain the towers, some 270 miles of road were laid and ten bridges were built. Fifteen camps were set up to house the workers.
The country’s hilly terrain and high winds made the project even more challenging. But as you’ll see, these men were practically unfazed. They sent bundles of steel across steep canyons on zip lines and hand-walked wire haulage rope across gullies because they couldn’t otherwise do their job. Six of these men could erect a tower within a few hours, which the filmmakers prove with a cool time-lapse sequence.
Splicing the mile-long conductors is done with 100-ton compressors. Each connection is covered with steel sleeve that must be centered across the joint for optimum transmission. How did they check this? By taking a bunch of x-rays with a portable cesium-137 source.
Thanks for the tip, [Dave] and [Bryan Cockfield].
Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.
HVDC lines are so cool. I was driving around through northern MN earlier this summer and saw a funky looking power line; hefty gauge with only two conductors. I looked it up later that day and it turned out to be the Square Butte line. I’ve always wanted to tour one of the converter stations, but so far it seems like they’re typically unmanned and quite dangerous.
Shirt collar, sweater and shorts will not get you an OSHA sticker. When men were men!
Yea in those days you’ed get decapitated in the morning and be back to work bu lunchtime!
and when we got home, our Dad and our mother would kill us. And you try and tell the young people of today that ….. they won’t believe you.
When men were men, and hard hats were good ol’ fashioned craniums.
Kept expecting Mike and the Bots to chime in. “Coronalux and Corona Light”
I’m thinking of submitting these retrotechtaculars as suggestions…
Ah, I long for the days of interesting documentaries like this, and not “Come dine with me”.
If like me you would love to see inside they Haywards substation where the DC is converted to AC. For that look for the “Inter-Island Power (1966)” video.
I used to regularly mountainbike under the northern end of the link, around where the truck was being pulled by the tractor…
Well, this is a retrotechtacular that is very very boring and maybe the first time I truly found it a too big of a waste of the time to watch it.
While it’s not a simple task, but it looks to me they simply strung up a half million volt HVDC transmission line anyway. :) Perhaps pratices have changed over fifty years, did the pull in that much line with out spooling it on layers so it pays out with trouble next time it’s used? Clearly they did.
What, no Hobbitts dragging lines through the gullies? Or Dwarves digging holes? At least there were a couple of sheep ;-)
Sorry, couldn’t help myself.
I was thinking Peter Jackson had to plan camera angles to leave those towers out of sight.
sitll using pretty much the same methods in india
( where l was recently bicycle-touring)
they don’t bother to build such fancy camps though, workers simply live in tents
( l wanted to camp with them, but the logistics never quite worked out)
Any reason why it is DC they are carrying? Perhaps AC at such a voltage would induce too much physical movement in the wires?
DC is preferable for a number of reasons. Because it isn’t alternating, there is no need to worry about synchronisation, so if you are connecting between multiple grids they don’t need to be locked together. Power carried is higher for a given peak voltage with DC (as AC power is RMS of peak voltage, whereas DC power is directly linked to peak voltage), so for a given peak voltage the DC system carries 41% more power? You also need fewer conductors with DC as you don’t worry about carrying multiple phases. All this means less metalwork to fly. There are also other issues like the AC systems to do with Skin Effect, which effectively increases the conductor resistance in AC circuits as the power isn’t carried equally within the conductor, meaning you need more metal for the same power for AC than DC. More metal = more cost – both because it needs more source material AND heavier duty engineering to carry it.
Listen steve edison, I think this discussion was had, and you lost, a hundred years ago.
Steve is correct. The economics work out for very high power long distance transmission.
And there we have his twin brother :)
The reason Edison lost the “war of the currents” back in the day was because there was no good way of stepping DC up and down in voltage at the time. If they’d had high-power inverters and rectifiers available in the 19th century, AC power transmission might never have taken off.
What the hell is wrong with you people. Because AC travels on the skin, this is why stranded wire increases surface area and is MORE capable of transmitting power. The higher the voltage the better for AC, and since a transformer is all that’s needed AC wins that battle hands down. One transformer and you can step down the super high transmission voltage 500kv to city wide transmission 20kv and another at each city block to 120v, keeping the voltage as high as possible, and easy to convert up or down. DC absolutely cannot do this. Not including AC single phase half-step amp wave is safer than DC. https://en.wikipedia.org/wiki/War_of_Currents#Electric_power_transmission
Also in buried and underwater transmission lines, AC systems has notable capacitive losses. The only advantage of AC over DC power lines is economic: It is a lot easier (and cheaper) to step up and down AC voltages than DC.
skin effect is a non issue at 60 Hz
It is, while you dodge most of the loss of the skin effect at 60Hz on the wire then due to the low frequency you’ll need huge expensive transformers, HVDC uses ultra high frequency transformers to be stepped up and down and has no skin effect on the wire, both of those factors (transformer cost and skin effect) are a balancing act with AC, the laws of physics aren’t known for handing out free lunches.
The avoidance of 1.414 higher voltage is the only argument for DC. The switching stations are expensive and demand failure proof lightning suppression. Not run with cheap help.
When I was studying electrical engineering in the 90’s my lecturer told me they used DC for this line because it goes under water (through the Cook Straight), AC would be less efficient for this purpose.
A wikipedia article on the topic states that capacitance between the lines is increased due to the dielectric properties of water (as opposed to air in overhead lines), therefore reducing the power factor of the system.
https://en.wikipedia.org/wiki/High-voltage_direct_current#Advantages_of_HVDC_over_AC_transmission
DC just has huge flaws.
And as for the skin effect with AC mentioned earlier, that’s an advantage in practice because you can use strong cores to carry the weight of AC lines and only the outer edge needs to carry the actual current.
But sure AC does have a few disadvantages, like the synchronization, And I’m sure in some cases like your example HVDC might be the best solution, but still though, there is actually a reason why the entire planet selects to use AC most often, and it’s not mere coincidence.
Dude, no one is claiming that DC is better for all transmission, but it is better for precisely this kind of high-power project. Chill out. AC is a hammer, quit pounding screws with it.
And, yes, I do have an EE degree.
You might not claim it, but it’s the internet, people will claim silly stuff and it’s picked up by other silly people and soon enough you are crucified if you aren’t on board and shout AC is always bad :/
Then in the worst case scenario the politicians will start taking replacing all AC with DC…
What huge flaws?
DC was always superior from an engineering standpoint for bulk transmission of power, read, point A to B via wire, because DC has no skin effect and it’s rms voltage is the same as it’s peak voltage, which means smaller losses as the same wire at the same rate of power transmission will always pose less resistance to DC compared to AC.
This is a fact, the laws of physics dictated so, and if you have to question it it’s only because you don’t know enough, even the basics, of electrical engineering.
This was already known at the time of the war of currents but the reason why AC won is that it’s efficiency was bigger from production to consumption (a more holistic view that considered all factors) which offsetted it’s demonstrably worse on-wire transmission capabilities (just one factor), meaning, AC was correctly chosen at the time, it was the winner and rightfully so, not anymore tough, technology has moved on, the thing now is that upgrading would be incredibly expensive as all the AC networks and machinery would have to be replaced with DC networks and machinery, which is insane, we’re talking probably trillions of dollars here, it’s likely that the cost is so big that we can live with the inefficiencies of AC for hundreds of years before we could recuperate the losses of switching to DC.
During the war of currents it was observed that DC needed much thicker wires, which leads the regular Joe’s of this world to think that that’s a characteristic of DC when it really isn’t, the approach was holistic as I said before and so the AC would be converted to higher voltage using transformers to then go across the thinner transmission lines, it was not economically viable at the time to convert DC to a higher voltage and brushless DC motors didn’t even existed at the time while AC ones did exist, were cheap, available and also very efficient, all of that has changed and is still changing.
It is about money. AC has a peak value 1.414 times the RMS or DC value. 50% more voltage means enormously more problems. Economics dictates DC.