Fleet Tankers Or Oilers ...

Utilities have been moving to higher voltages to push more juice down the line without having to rewire, so your info may be dated. There is also variation from company to company depending on their system design preferences.

I thought our local distribution voltage was 16kV - until I noticed a warning sign for overhead wires on a construction site the other day. Marked '21kV'. [the equipment operators don't actually give a damn about the voltage, they don't want to contact the lines regardless. i presume the info is there in case of need] 20kV was the standard in much of Europe, but they may have moved higher as well, for the same reason.

Castenea wrote:

darrell wrote:At 17,000 volts, which is the most common voltage for power lines in residential areas in the US, 1 GW would require 588,235 amps, which would be a main bus bar of 2,000 square centameters, or 44 CM (18") on a side, so now we know how spanner got his name when he dropped one.

I thought the standard distribution primary in the US was 11000 volts to ground or 13.3KV phase to phase. Homes generally have a transformer pulling from one phase and delivering 120V to ground to the house. Large buildings (e.g. 20 apartments) can have 13.3KV three phase going into a transformer in the basement. I have heard of factories who have 3-phase 33KV going into a substation in the building. I believe 33KV is the largest distribution normally seen in the US.

Castenea wrote:

darrell wrote:At 17,000 volts, which is the most common voltage for power lines in residential areas in the US, 1 GW would require 588,235 amps, which would be a main bus bar of 2,000 square centameters, or 44 CM (18") on a side, so now we know how spanner got his name when he dropped one.

I thought the standard distribution primary in the US was 11000 volts to ground or 13.3KV phase to phase. Homes generally have a transformer pulling from one phase and delivering 120V to ground to the house. Large buildings (e.g. 20 apartments) can have 13.3KV three phase going into a transformer in the basement. I have heard of factories who have 3-phase 33KV going into a substation in the building. I believe 33KV is the largest distribution normally seen in the US.

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kzt wrote:12.47 kV is the delivery voltage I see marked on feeder conduits and transformers around work.

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Louis R wrote:Utilities have been moving to higher voltages to push more juice down the line without having to rewire, so your info may be dated. There is also variation from company to company depending on their system design preferences.

I thought our local distribution voltage was 16kV - until I noticed a warning sign for overhead wires on a construction site the other day. Marked '21kV'. [the equipment operators don't actually give a damn about the voltage, they don't want to contact the lines regardless. i presume the info is there in case of need] 20kV was the standard in much of Europe, but they may have moved higher as well, for the same reason.

There was a reason that I said most common voltage. There is no standard voltage, with the range between 11KV-25KV for residental areas. The most reacent info I could find has 35% of residental systems at 17KV.

Manufacturing districts often have higher voltages to account for the big motors used, typically in the 25-50KV range.

darrell wrote:There was a reason that I said most common voltage. There is no standard voltage, with the range between 11KV-25KV for residental areas. The most reacent info I could find has 35% of residental systems at 17KV.

Manufacturing districts often have higher voltages to account for the big motors used, typically in the 25-50KV range.

My knowledge comes from talking to arborists who do line clearance. Thus 11KV single primary needs ~3ft of clearance, 13.5KV gets a box of about 3ft by 20ft (to accommodate all three phases), and 33KV gets about 20 ft of clearance. That the voltages have increased does not shock me, as my info is third hand and probably over 10 years old. I have seen 33KV go into a substation that then feeds 3+ 13.5KV feeders. Trees on primaries are bad news.

Castenea wrote:

darrell wrote:There was a reason that I said most common voltage. There is no standard voltage, with the range between 11KV-25KV for residental areas. The most reacent info I could find has 35% of residental systems at 17KV.

Manufacturing districts often have higher voltages to account for the big motors used, typically in the 25-50KV range.

My knowledge comes from talking to arborists who do line clearance. Thus 11KV single primary needs ~3ft of clearance, 13.5KV gets a box of about 3ft by 20ft (to accommodate all three phases), and 33KV gets about 20 ft of clearance. That the voltages have increased does not shock me, as my info is third hand and probably over 10 years old. I have seen 33KV go into a substation that then feeds 3+ 13.5KV feeders. Trees on primaries are bad news.

and the actual voltage is determined by the power company. For example, in phnoneix, APS electric uses one voltage on their transmission lines, SRP uses a different one. So your voltage might be 11 KV.

kzt wrote:12.47 kV is the delivery voltage I see marked on feeder conduits and transformers around work.

Most common source is 20KVA in USA for overhead power in residential areas. Any other area with more commercial and it will be higher. If far from a station will be lower. In your example kzt, 20KVA from source most likely, but due to being in a conduit and heating problems on the insulation etc, will be downrated. Depending on conduit size, feeder type etc will change its rating to ~12KVA.

PS. To someones bus bar size upthread comment, due to skin effect your calc is not correct for AC(unless it was a massive glitz wire connection), but may be true for DC(No I did not run the calc) Besides neither is true either as this high of voltage creates a spark gap problem requiring feet of distance in air. On a starship, they may run lower O2 atmosphere, or place the interconnects in complete vacuum.

I've been under a busbar short. Only 50vdc @ 800 amps.
I think the bars were about 4in by 1in. Might have been 6in.
I was about 8ft below them.

Still got the jumper with the burn marks in the back.

We ended up parting a 1in copper cable with a broom to break it. (No fusing as it turned out.)

Oh, it wasn't a simple short but a short to grounded metalwork.

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it's the amps that cramps, not the volts that jolts

I dont have the text handy, but I distinctly remember a conversation between either Lester Tourville or Javier Giscard and their commissioner, in I think Ashes of Victory, where they discuss the "Manty Super LACs" and how likely it was they could really exist.

The primary issue was the mass or volume required by an "all-up" fusion reactor capable of powering a warship (the "hip pocket" reactors used in pinnaces couldnt do it) and the observed size of the LACs themselves.

From everything they knew it wasnt possible to squeeze a fusion reactor and the weapons observed into a hull "much under 50k tons", which was far larger than the observed size of the Shrikes.

I had a thought, why not put a fission reactor in other ship-types other than LAC's? I'm not talking about using it as a primary energy generator, rather more like a backup plant that doesn't need fuel and can be spun up on short notice.

Pros and cons of the idea? Tactical advantages? Surprise factor?

Joat42 wrote:I had a thought, why not put a fission reactor in other ship-types other than LAC's? I'm not talking about using it as a primary energy generator, rather more like a backup plant that doesn't need fuel and can be spun up on short notice.

Pros and cons of the idea? Tactical advantages? Surprise factor?

You could on the technical level, but I'm having trouble finding a significant reason to bother.

OTOH a fission reactor can be brought critical using virtually no power, where a fusion reactor appears to need some fairly hefty power to bring up the grav field and kickstart the reaction. So you could shut down all your fusion reactors and then use fission to bring them back online.

But most ship missions don't involve hanging around for ages in fuel conservation mode.


Also, on a starship scale (where you don't have the scaling or whatever issues that make fusion in LACs so shockingly inefficient) fusion fuel is more compact per unit of energy than fission fuel. So if you were in fuel conservation mode you could last longer by using additional hydrogen tanks the size of the fission core.

Actually what you'd probably do if you needed a ship with a truly prolonged low power idle state is run the fusion reactors intermittently. Use it to fully charge every superconductor on the ship, then shut down the fusion plants. Run off the stored power until you got down to restart power + acceptable safety margin; fire up the plant, run it just long enough to top off stored power, and shut it back down. That would let you run the fusion plant at it fuel efficient high level output; but only when needed.

You should be able to last longer than on fission power, yet not need to find room for an otherwise redundant fission plant.


But it's possible there's some scenario I'm missing where you need fairly long endurance medium levels of power on a starship and aren't willing / able to just run the high power level fusion reactors.