[HN Gopher] Reconductoring: Boosting U.S. Grid Capacity Efficiently
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Reconductoring: Boosting U.S. Grid Capacity Efficiently
Author : rbanffy
Score : 66 points
Date : 2024-09-25 14:22 UTC (1 days ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| pdx_flyer wrote:
| The article doesn't say much about it but I am sure there is
| significant work being done at the transmission substations as
| well to support the extra capacity.
| ghouse wrote:
| As the new conductors will have lower impedance, some breakers
| may need to be replaced to interrupt higher fault current.
| Otherwise, it's likely the only substation equipment needing to
| upgrade would be series compensation stations which may have
| lower normal and emergency ratings than the upgraded
| conductors.
|
| More likely is that lower impedance on the reconductored
| circuit will cause increased flows on other, non-upgraded
| circuits, either requiring those to be reconductored, or
| installing phase-shifting tranformers or reactors to limit
| current.
| sitkack wrote:
| If substations are being upgraded, they should also be
| installing batteries and inverters at the substations at the
| same time.
| infecto wrote:
| This sounds like moving the goal and a much more difficult
| problem than just upgrading the substation.
| pdx_flyer wrote:
| Good points.
|
| Have you seen a lot of phase-shifting transformers in the
| U.S.? In my experience they've mostly been in Europe with a
| few specialized applications in the States.
|
| I would think a utility would want to reconductor the other
| circuits otherwise they're leaving benefits on the table
| right?
| ghouse wrote:
| I only know the western US. And my experience is consistant
| with your own -- specialized applications.
|
| They would love to reconductor the other circuits. In the
| US, the utilities make a guaranteed rate of return on
| investments in the transmission system. So, anything they
| regulators will let them do, they'll do -- not necessarily
| because it has technical benefits, but because it has
| economic benefits.
|
| This is one reason why reconductoring isn't that popular
| with utilities -- it allows the utility to get more
| capacity with less spend, so less profit.
| specialist wrote:
| Spot on. David Roberts (Volts) also asked about that in one of
| his interviews.
|
| IIRC, the expert answer was: substations generally need a
| retrofit (eg new transformer, breakers, smarts).
|
| Even so, reconductoring is much faster and cheaper than
| building new lines.
|
| Because retro doesn't require a new permit, often reuse
| existing footprint, and substations can be upgraded as needed
| (eg only for sections pushing more power).
| outside1234 wrote:
| There is also a parallel technology that does a better job of
| understanding line conditions with regards to heat, humidity,
| etc. and enables higher utilization as well (versus having to
| rate the lines to the worst 20 year scenario).
| ghouse wrote:
| You may be referring to either 1) the real-time line ratings
| (directionally required by FERC order 881, or 2) technology
| like the "SmartValve" from Smart Wires which dynamically
| adjusts impedance to keep conductors within their operating
| envelope.
|
| Among risks that are managed is ground faults caused by sage
| (as the line heats, it expands, getting closer to the ground),
| or 2) annealing which is a permanent expansion of the conductor
| due to operating too hot for too long. The advanced conductors
| use composite cores allowing the conductor to carry more
| current at a higher temperature with reduced risk for
| annealing.
| specialist wrote:
| Good explainer, thanks for posting.
|
| Volts recently interviewed Emilia Chojkiewicz of UC Berkeley
| (quoted in article) and Jason Huang of TS Conductor.
|
| _" One easy way to boost the grid: upgrade the power lines"_
| [Jan 31, 2024] https://www.volts.wtf/p/one-easy-way-to-boost-the-
| grid-upgra...
|
| Here's a prior episode about "grid enhancing technologies" in
| general, including reconductoring.
|
| _" Getting more out of the grid we've already built"_ [Sep 13,
| 2023] https://www.volts.wtf/p/getting-more-out-of-the-grid-weve
|
| Grids are a common topic on Volts. Permitting, policy,
| intransigent utilities, open data standards, biz models,
| decentralization, virtual power plants, creating a national grid,
| etc.
|
| A handful of climate crisis / net-zero podcasts like Volts
| connect and catalyze people, resulting in new startups,
| legislation, and giving people hope & energy.
|
| Highest recommendation.
|
| Aside:
|
| INTERGRID is my term for our future perfect grid-of-grids.
| Inspired by the internet, of course. One such effort is
| (Alphabet) X & AES' Tapestry project
| https://x.company/projects/tapestry/ .
| cool_dude85 wrote:
| Strange not to mention wire weight which I gather is an extremely
| important factor. If these are also heavier, they may sag more
| for strictly physical reasons and that would cause problems. I
| guess the modeling behind this article probably takes that into
| account.
| ghouse wrote:
| Increased weight makes reconductoring much more difficult as
| the structures are designed to carry specific weight. Increased
| size can also impact structure loading from ice or wind. So,
| generally, reconductoring does not materially increase weight.
|
| The primary difference between the traditional conductors and
| advanced conductors is temperature tolerance. Most transmission
| lines are aluminum conductors with a steel core for strength
| (ASCR). As current increases, so does temperature, causing
| lines to sag (or the steel anneal if too hot).
|
| Advanced conductors use a different composition to operate at
| higher temperatures, or otherwise carry more current (one
| example: aluminum conductor, composite reinforced, or ACCR) so
| as to have similar weight (and profile) to the original,
| traditional conductor.
| elihu wrote:
| > "Chojkiewicz and her colleagues at Berkeley's Energy and
| Resources Group and Goldman School of Public Policy studied the
| use of advanced conductors that wrap more aluminum around a
| smaller, stronger composite core. These Aluminum Conductor
| Composite Cores (ACCCs) are more conductive and can operate at
| higher temperatures, resulting in roughly a doubling of
| capacity for an equivalent diameter wire."
|
| It isn't clear from the text, but the wires might not actually
| be any heavier, given that they replace the steel core with a
| composite.
|
| Aluminum is about 2.7 g/cm^3, whereas steel is around 7.85.
|
| I'd imagine they can switch to a slightly smaller cable size if
| they have to keep to the original weight and a new cable
| happens to be a little heavier at the same diameter.
|
| I'm kind of surprised they don't lose the advantages of
| stranded cable when switching to something that looks more like
| a solid cable. As I understand it, for AC wiring you usually
| want a lot of strands because most of the current tends to
| travel on the surface. Maybe that's less of a thing for high
| voltage. Or maybe the seams between the strands are enough to
| cause the skin effect even if they're tight-fitting.
| tuatoru wrote:
| Skin effect is a high-frequency thing. From memory the down-
| rating tables start at 100 kHz.
| Kirby64 wrote:
| Skin effect works at all frequencies besides DC. At 60 Hz
| it's 8.5mm. So, solid conductors thicker than 17mm have
| some skin loss. You can mitigate this by winding multi
| strand wire in a particular way, though.
| Animats wrote:
| Composite-core cables are lighter. The core is carbon and
| fiberglas fiber, rather than steel.[1]
|
| [1] https://compow.com/blog/midal-accc
| gok wrote:
| previously https://news.ycombinator.com/item?id=39485940
| wernerb wrote:
| These cables can run much hotter and so have better capacity. BUT
| there is a big downside. Because they run so hot (you can grill a
| burger on them with ease), there will be a lot more resistance
| resulting in net losses. Also fun, because they can run so hot
| when rain hits it literally sizzles and cooks resulting in extra
| noise.
| SketchySeaBeast wrote:
| Isn't that going to be a fire hazard as well?
| aerostable_slug wrote:
| They already need to be kept away from vegetation to prevent
| faults.
| jeffbee wrote:
| Something that everyone is going to need to get used to is that
| with carbon-free, cost-free primary inputs the emphasis on
| efficiency that we have historically known is going to
| disappear. It fundamentally does not matter if something that
| we need to make the system work loses a few percent of the
| energy.
| Krssst wrote:
| It does when the grid is running on batteries for extended
| periods of time. I guess it just comes down to what is
| cheaper between x% more batteries and y% larger conductors.
| cameldrv wrote:
| If the solar is remote and the batteries are near the load
| though you don't need any more batteries in this situation,
| just more panels.
| thfuran wrote:
| That doesn't sound free.
| theamk wrote:
| Wow! A random datasheet[0] says:
|
| "Max.allowable continuous operating temp: 175 C", and shows a
| current capacity plot from 55C to 175C. That's 350 F,
| definitely enough to grill burger.
|
| Also, I was curious about power loss - for that one cable I
| found, it's 0.25816 O/km @ 660 amp, which comes out to 181
| kilowatt of loss (150 average US homes) per mile of the line
| (and probably double that for second wire). That's a lot of
| loss!
|
| [0] https://www.midalcable.com/storage/products/accc/accc-
| data-s...
| bsder wrote:
| It's not particularly cheap or effective. From the article:
|
| > Chojkiewicz says her team's modeling neglected those
| alternatives because their goal was simply to lay out the
| "nationwide potential," of reconductoring.
|
| They only compared it to buying new land and putting in
| completely new lines.
|
| They ignored simply increasing the voltage, switching to HVDC and
| any solution other than "putting in whole new lines".
|
| In particular, the fact that they just ignored HVDC is
| problematic. HVDC gets you not just cheaper transmission but
| _lower losses_ so makes better use of what you have even if you
| don 't immediately boost capacity.
| 7952 wrote:
| HVDC converter stations are expensive though. And you would
| need to have one every time you have a substation to directly
| replace an AC cable. It makes sense for longer distances.
| mastax wrote:
| Wouldn't increasing the voltage require new towers in most
| cases? The towers are sized to give sufficient isolation.
| bsder wrote:
| Maybe. But it wouldn't require new land.
|
| And new towers with simply higher voltage on the old cables
| may be cheaper than these really expensive cables. And has
| the advantage that you can upgrade towers piecemeal as part
| of your maintenance cycle.
| matt-p wrote:
| HVDC is not a silver bullet.
|
| Converter stations are very expensive and also take more space.
| You need one every time you tap in/out of the transmission
| line, great for point to point links say Offshore windfarm to
| major IC, but general transmission gets tapped into and out of
| much more frequently. Even if today you plan for this link to
| be P2P from city A > city B today what happens tomorrow when
| someone builds a generation plant, or a new town, datacentre
| campus on that route?
|
| The "efficiency" gain is debatable, you do lose less on
| transmission but you now have this cost of getting from DC>AC
| AC>DC which costs roughly 1.1-1.6% - in the grand scheme of
| things for most schemes any overall efficiency gain is marginal
| to nil.
|
| Overall the most flexible thing to do is build AC at the
| highest voltage your towers/interconnect points support (and
| consider increasing that).
|
| In the UK we are building more lines and converting more
| substations from 275KV to 400KV.
| quickthrowman wrote:
| > They ignored simply increasing the voltage
|
| For good reason, you can't do that.
|
| Electrical distribution conductors are insulated by air (and
| distance). If you crank up the voltage, you could have line-to-
| line arc flashes if you don't increase the conductor spacing.
| Increasing the conductor spacing requires new towers, so...
| sidewndr46 wrote:
| I thought the advantage of HVDC was mostly for subterranean and
| undersea cables. Why would it be better above ground?
| mikewarot wrote:
| I was hoping Ultraconductors[1,1a] would make it out of the lab,
| and into general use... but the crash of 2008 apparently killed
| them off. (OR... it was a scam all along. The patent they
| reference [2] is for a polymer about as conductive as the
| nichrome wires you use in your toaster)
|
| The other patent they reference[3]... does claim 10^11 S/cm,
| which is about a million times as conductive as silver.
|
| Imagine what you could do with power cables a million times as
| conductive as silver.
|
| [1] http://www.superconductors.org/ultra.htm
|
| [1a]
| https://web.archive.org/web/20090201200804/http://ultracondu...
|
| [2] https://patents.google.com/patent/US5777292A/en
|
| [3] https://patents.google.com/patent/US6552883/en
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