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Can you talk more about how the heck you can turn circuits on and off under these sorts of currents and voltages? Isn't ionization of air related to voltage so with high voltages, air is no longer enough of an insulator (eg: if you just try to mechanically withdraw a metal contact it will form a spark and ionize the air)? I also wonder how the contacts aren't fried even if you don't have arc issues keeping the thing energized... a contact that large made of gold or silver would be freakin' expensive, but anything else is going to quickly corrode. Also re:Texas, yes most of Texas is on its own independent power grid. We have several DC-DC connects with the eastern grid and one with the western grid IIRC. These are DC-DC but all housed in the same building so the transmission losses aren't an issue - it is the frequency synchronization issue mentioned above. You can check out the current wars article on wikipedia but DC is more efficient, it is just harder to make simple motors and until solid state electronics, there was no easy/cheap/small way to step DC voltages up and down (but transformers for AC power are trivially easy to make). So we deployed AC because we needed higher voltages to move power long distances, but we had no way to step DC up and down, thus AC won the current wars. You should check out the mercury arc rectifiers... some of them were huge 6-8 ft glass bulbs where A/C was injected at the electrodes at the bottom and as the AC phases made their cycle, the arc would pass between different electrodes, resulting in a somewhat stable DC output. The mercury vapor would hit the glass, cool, condense, then trickle back down to the pool at the bottom. I find it ironic that the vast majority of devices people use these days (at least in the home or office, not the plant floor) run on DC power... everything except stuff like heating elements and large motors. We waste so much electricity piping AC long distances then converting it into DC... its almost like we would have never deployed AC power if we could have made cheap DC voltage changers back in the day. It's also why places like data centers are starting to install a few central rectifiers then deploying DC power hookups to the servers/equipment... then all the PSU does is simple voltage conversion, which helps control heat and makes the PSU more reliable. I'm not sure if they approved standard outlets and whatnot for DC power yet. Three-Phase posted:I really doubt it, especially since rectifying AC to DC is so much easier using power diodes and SRCs than, say, a mercury arc rectifier like the used to, or a motor-generator set. With the SCRs and some filtering, you can create DC at varying voltages as well. This is good for applications like electroplating, welding, etc. IIRC there were still a few DC customers in the NY area (from the original edison days) but they were switched over in the 1990s/early 2000s by installing rectifiers on-site. Also the last mercury arc valves were replaced with solid state devices (or at least that was the plan last I heard... I'm no expert). I believe the costs for these devices are continuing to fall and it is likely that in the future HVDC will be much cheaper to implement. Of course they are also testing superconducting transmission lines using liquid nitrogen cooled wires. In theory a very small wire could carry massive loads... as long as it never warmed up... then I expect "vaporized" wouldn't do justice to what happens to it. Simulated fucked around with this message at 00:54 on Sep 4, 2011 |
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Sep 4, 2011 00:47
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Three-Phase posted:1. (Smaller/medium breakers) Have arc chutes - when the breaker opens, the arc flows up into these dividers, gets split up and cools, until the arc cannot sustain itself Doesn't the arc in these sort of situations degrade the contacts? I presume there would be a limited number of disconnects before it is no good... actually I think the cheap non-silvered home light switches have the same issue. I know I've had to replace one or two that would audibly arc when switched on/off and I presume that was due to oxides and crap building up on the contacts. quote:Also, breakers have an AIC - ampere interruption capability. So you buy a 120V, 20A breaker, it may have a 10,000 AIC. What that means is that for a fault under 10,000A, the breaker should be able to interrupt the arc. If it's over 10,000A, it may not be able to stop the arc (and will probably blow up in the process.) You need to look at the makeup of the power system and say "gee, this breaker is only rated at 10,000A. If I short out what this is connected to, will more or less than 10,000A flow through it? Will something else break the circuit in time?" Awesome. I also like the video of the oil-cooled transformer exploding as it superheats the oil. Not sure what would cause that though, given the oil they use is non-conducting. I would presume most people who try to flip a non-load interrupting switch aren't around to talk about it. Do they usually have safety sensors to prevent you from operating it while under load? For that matter, it makes me wonder how industrial equipment can be switched on and off... or even if it can be switched off internally. I have no idea how you'd make a regulator that could control the motor speed of a 10,000 HP motor.
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Sep 4, 2011 01:09
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Crackpipe posted:What parts of these would be safe to bump into? I've always viewed substations as death mazes where bumping into absolutely anything will kill you instantly. Indeed, it looks like a death trap to walk around in there while energized. I presume there are designated foot paths that have a somewhat lower chance of electrocution.
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Sep 4, 2011 23:19
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n/m
Simulated fucked around with this message at 23:07 on Sep 14, 2011 |
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Sep 5, 2011 18:11
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Thanks for the info; I'm still trying to understand reactive and PF and revise it into a layman's explanation.
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Sep 7, 2011 02:59
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helno posted:That sounds like bull to me. The coal plants in these parts are used for load foallowing and are up and down on a daily basis. I was always under the impression that it took a long time to restart a coal plant from cold shutdown. Obviously they can vary the load day to day, but that's not the same as being turned off.
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Sep 14, 2011 23:24
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Concrete holds moisture so it makes sense that it conducts (plus I have personal experience being shocked by a faulty appliance while standing on it). Also around here ground rods have to be driven quite deep due the hot summers and for precisely the reasons you'd think. Oh and ground isn't always zero volts which is where ground loop hum comes from in audio systems... Two paths to ground that have slight differences which results in a current flowing between them through the interior wiring which manifests itself as a hum. Or it can be due to voltage drop, etc... Someone more knowledgeable may be able to chime in on that.
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Jan 18, 2012 16:48
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How is that even possible without everything exploding?
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Apr 22, 2012 08:06
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The Cleaner posted:Sure here's a Google Map satellite of the spot. Placebo/psychosomatic effect. I used to get this too, even though I knew it was new-age bullshit about "waves". I finally made myself sit under the power lines for a few minutes, the feeling went away, and it hasn't happened again. This was despite knowing logically that it was all bullshit. Your brain tricks you and knowing it's a trick doesn't always remove the illusion.
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Nov 13, 2012 16:47
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edit: carry on.
Simulated fucked around with this message at 00:21 on Nov 15, 2012 |
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Nov 14, 2012 17:54
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