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Three-Phase posted:Actually, there are a lot of industrial applications that need batteries that are similiar to, but much larger than, car batteries. Basically, car batteries are designed with a lot of internal surface area on the lead plates to give a very short burst of high current. DC backup power for switchgear and telephone exchanges are sized to power very small loads for 8 or more hours, often days. UPS batteries are designed to drain over a period of, typically, 5-15 minutes. Deep cycle batteries like these can deep-cycle hundreds of times without significant reductions in capacity; deep cycle a car battery just a handful of times, though, and the delicate structures get destroyed and you're liable to be shopping for a new car battery. Car batteries have much lower internal resistance than UPS/telex batteries and would be better for welding. Maybe if your jeep broke down in the middle of the sahara you could spot weld something back together with jumper cables and some ingenuity, but I don't think it would be cost effective due to the damage you'd do to the batteries. grover fucked around with this message at 01:48 on Feb 23, 2013 |
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Feb 22, 2013 17:49
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Crap. You're 100% right Grover.
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Feb 22, 2013 22:09
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Thanks for the answers, guys. It seems like short bursts would also be necessary because if you're using car batteries to weld you probably don't have a proper UV shield lying around.
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Feb 23, 2013 19:58
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(Full disclosure: this is a crosspost.) I was playing around with some equipment modeling/rendering in Art of Illusion.  I don't think I've seen any actual transformer that have the H taps setup that way, it's like using some kind of pothead that's for an outdoors installation indoors? I'm thinking about tweaks to make this more realistic. Any suggestions? Three-Phase fucked around with this message at 14:36 on Feb 24, 2013 |
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Feb 24, 2013 14:21
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I hope someone can answer this here. For electric trains, how does distribution work? I think I saw a couple of taps of to transformers along the train ride. Do those transformers have to worry about being in phase? I know this train line is a couple hundred km long, so frequency has to drift along the length of the cable, right? Is a few hundred km just not long enough to worry about?
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Mar 3, 2013 13:59
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babyeatingpsychopath posted:I hope someone can answer this here. Electric train track will often have sections with insulated breaks between them. It's set up so that the part of the train on one section can drive the remainder across the break. The reason is usually more about voltage drop and maintenance issues than phase, since the wavelength of 60 Hz electricity is rather long (although inductors such as transformers will introduce phase shifts).
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Mar 3, 2013 23:07
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I was reading that throughout the world there are varying voltages used in a lot of these trains - including DC and low-frequency AC. Voltages as low as 600VDC and as high as 25kVAC. Whatever the voltage, if for any reason you find yourself standing on top of a train, never grab or go near the power wire. There's a  video (that won't be linked to) of this on YouTube and Liveleak. In that case contact was believed to be instantaneously lethal. 
Three-Phase fucked around with this message at 02:06 on Mar 4, 2013 |
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Mar 4, 2013 02:00
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Three-Phase posted:I was reading that throughout the world there are varying voltages used in a lot of these trains - including DC and low-frequency AC. Voltages as low as 600VDC and as high as 25kVAC. Know exactly which video you're talking about : https://www.youtube.com/watch?v=tjJdE_4tgfk
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Mar 4, 2013 02:04
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Well, I guess we crossed that Rubicon. There was a discussion at work about whether the man actually touched the line, or if it jumped over before he actually touched it. At 11kV, I could believe that once his had was less than a few inches or so from the line, it would definitely jump over to his hand. (I believe OSHA lists 10 feet as the minimum safe distance 0-50kV.) Yeah, that guy really got thumped. Oh, what the hell. Here's another video of a man on drugs who is swinging on a transmission line. Spoiler: it ends pretty badly for him, and may have also disrupted the power transmission system. https://www.youtube.com/watch?v=6FrcZFf2Xg8 He may have survived*, who knows. I saw smoke from the ground line connection up top. It makes me wonder if these transmission line phases are ground-referenced, or have a high resistance or impedance ground. Considering this is transmission voltages, I'm surprised the guy didn't simply get blown apart by the fault energy. He seemed to stay in one piece. * - About as likely as Ron Paul becoming president. Three-Phase fucked around with this message at 02:22 on Mar 4, 2013 |
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Mar 4, 2013 02:11
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I thought this video was pretty cool https://www.youtube.com/watch?v=EWbBdAeW1m8 I always get curious about what voltages go through transmission lines. Is there any way to be able to tell?
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Mar 4, 2013 02:41
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It's burgin' time! 
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Counting the number of bells on the string insulators will give you a rough idea. 8-9 bells = 138kV in Alberta. The type of tower might also tell you - generally it's wooden H-frame structures for lower voltages and steel structures for higher ones, but I played under a 138kV line with steel lattice structures as a kid.
Colmface fucked around with this message at 02:49 on Mar 4, 2013 |
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Mar 4, 2013 02:47
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I don't know what it is, but climbing those towers and riding spacer carts seems like a fun job. I heart bacon's video just makes me more interested in it.Cheesemaster200 posted:Please give me work... This is from way back in the thread, but at least in power systems handling a few hundred amps of DC, you use a current measuring resistor (a few milliohms, even less in this case, possibly even just a length of the wire used in the physical plant) with two test points. Measure the voltage across the resistance (or section of wire), divide by known resistance (possibly correcting for temperature), and you have current. Do that on both the negative and positive, currents should be equal and opposing. it's almost like building a kelvin resistance bridge into your power delivery wiring. grover posted:You can't do it with caps, not with any real success. There are ways to do it, but they're more complicated than just using a cap, and it would be cheaper to sell the 3-phase rectifier and buy a 1-phase. wrong. Capacitors in series are like resistors in parallel, overall capacitance goes down. You can run it derated... if you add more filter capacitance in PARALLEL with the existing filter caps. Depending on the lamp (high pressure xenon arc lamp?) it may or may not be really pissed off if run below rated output. I'd consider upgrading the rectifiers - or even go to an active power factor correction type unit, which is effectively a bridge rectifier, then instead of feeding a filter bank directly, it feeds a buck/boost converter running at a high enough frequency that it can dynamically convert most of a rectified sine wave into pure DC. It's not truly power factor correction (since even with a basic dumb rectifier/filter setup, current and voltage are perfectly in phase) but more a harmonic distortion reduction system, since with your basic rectifier bridge and filter cap, the rectifiers will only conduct at the peak of the wave when Vripple > Vforward, resulting in horrible harmonics, basically a massive current spike right at the peak of the wave and no draw at other times. I've seen control chips (such as the On Semiconductors NCP1650, iirc) that can achieve 95% pure power (i.e. sub 5% THD) pretty easily, though you'd need to make use of some pretty heavy duty MOSFETs/IGBTs/thyristors to do this for an HP xenon lamp supply. You could also look into a cheap TIG/plasma cutter inverter setup, they include almost all of the same electronics and could probably be either configured or customized to perform adequately while still being cheap due to mass market availability. grover posted:Good inverters use pulse width modulation (multiple square wave pulses), which, when ran through an inductive filter, creates a near-perfect sine wave. It's quite easy to use PWM with modern IGBTs, and it surprises the hell out of me that not more devices use it. Saves a few cents and most people don't notice, I guess. High end stuff uses it exclusively. The waveform below is old style PWM, but the newest generation uses pulses fired at tens of thousands of Hz, which allows the use of very small inductors. Many buck/boost units are actually running f_osc up into the 10s of MHz range these days. The Cleaner posted:Maybe a silly question but I've never gotten an answer... I guess you've never gotten an answer you wanted... Apparently "everyone" already gave you the one you didn't want. I'm with them. Hell, I've camped out on a friends land under some power lines, strung my hammock up in between the legs of one of the towers and fell asleep watching the corona arcs over me, never got a headache there in the 3 years I've known the dude. What I saw when I woke up:  The climbing pegs on the corner of a tower make great coathooks:  grover posted:Those batteries are designed for different applications than car batteries, though, and have different properties. Done this. If you intend to use this as an emergency plan, bring some stick electrodes with you (the smallest ones you can find, of a metal/flux composition you're familiar with welding with) and at least a set of brazing goggles, preferably an actual welding mask. We used coathangar wire, three pairs of sunglasses, and two batteries in series to weld the caps on a ujoint into an axleshaft to hold it together well enough to get my jeep off the trail. No apparent damage to either battery, both were well used already and a year later neither has issues. Welds broke a few thousand feet further down the trail but it was enough to get to a spot where I could limp it out.
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Mar 4, 2013 04:59
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kastein posted:wrong. Capacitors in series are like resistors in parallel, overall capacitance goes down.
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Mar 4, 2013 12:26
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Hope this fits in this thread. I see these type of motors in our Asphalt plant which seems to be considered industrial just not huge. Question on Induction motors. In this video https://www.youtube.com/watch?v=J2guzKTBFdg&t=585s, PhotonicInduction holds the shaft of an Induction motor so that it doesn't spin. It only sounds like it is spinning. If he is able to prevent it from starting with just his hand, how do induction motors get enough torque to drive an actual load? Or is he doing something special when controlling this motor to reduce the torque so he can stop it with his hand.
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Mar 4, 2013 21:46
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SmartDrv posted:If he is able to prevent it from starting with just his hand, how do induction motors get enough torque to drive an actual load? Or is he doing something special when controlling this motor to reduce the torque so he can stop it with his hand. Really high-level explanation: The induction motor has a squirel-cage winding inside of it. When you apply current to the stator, it magnetically couples to the rotor. It's like a shorted secondary on a transformer. You have current flowing through the stator and the rotor. The magnetic field from the current generates a force that pushes the squirrel cage winding. As the three phases oscillate up and down, it pulls the rotor around. (I think that synchronous motors are actually easier to explain than induction motors.) Many synchronous motors are built with "armitissour" windings (don't ask me how to spell that) which is basically a little induction motor built inside the synchronous motor. The inverter might have current limiting on it. That's where the inverter would measure the current going into the motor (even looking at just one phase on cheaper ones). This would make sense if you were using that drive for something like a conveyour belt that could easily get overloaded or jam, and you want it to go back to running normally once a jam has cleared. If it sees the current skyrocket, it can change the voltage and frequency so it doesn't overload the motor. Also he's running a motor made for 50/60Hz at 400Hz. It's going to try and spin much, much faster. (A standard two-pole induction three-phase motor at 60hZ will spin at 3600RPM, 1800 with four poles, and 900 with eight.) Also, 1KW is just around 1.5 horsepower. That motor looks larger than 1.5HP. If you take a standard 480V motor, connect it across the line with no protection (themal-magnetic circuit breaker, overload, or relaying) and mechanically jam the rotor, the current draw will go through the roof. It will eventually smoke the lamination and the motor will fail. When an induction (or synchronous motor with armitissour windings) starts, it can pull like 12X the normal current. The motor is built to handle high inrush for a short period of time from a fraction of a second to tens of seconds for a large motor (thousands of horsepower). Three-Phase fucked around with this message at 23:51 on Mar 5, 2013 |
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Mar 5, 2013 23:48
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Three-Phase posted:Also he's running a motor made for 50/60Hz at 400Hz. The frequency can actually be used to control the torque at full slip (when the output shaft isn't turning) with higher frequency producing larger torque. The thing is the torque curve isn't flat like that of a petrol engine, it starts low (current limited), dips then goes to a peak as the output frequency goes up then dramatically falls (breakdown). This peak is where the motor operates at and can be 200-400 times the torque at full slip. Also he is applying a torque where he changes how hard he twists as he feels movement to always cancel out the motor, when it is a static load it applies a mass moment of inertia, so no matter how small the torque applied is (as long as it can overcome friction) the mass will begin moving. The caveat is it may take some time to get to full speed, and if the mass moment is too large the motor can burn out during this time.
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Mar 6, 2013 03:25
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http://www.baltimoresun.com/business/bs-bz-jonathan-libber-smart-meters-20130317,0,4437036.story I want to hit these people, repetitively.
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Mar 25, 2013 14:42
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Cheesemaster200 posted:http://www.baltimoresun.com/business/bs-bz-jonathan-libber-smart-meters-20130317,0,4437036.story Journalists have no idea why this is nonsense, leading to stories like these. I saw this documentary on mobile phones potentially causing brain damage due to heat. It wasn't all quackery, research showed that prolonged phone use causes pretty dramatic heat rise in kids brains and they're not sure if this is bad long term. But because 'radiation', they had some electro-smog nutjob explaining that all radiation is very dangerous, from mobile to WiFi to AM radio waves (really now). There was no explanation given how exactly it was dangerous, but look: now doctors have determined that holding a transmitter right next to your head can heat it up so *all* radiation must be harmful as well. If the interviewer had just asked anyone with a physics degree for an explanation of ionizing radiation it would've put that in perspective, but instead they opted to leave it at WE JUST DON'T KNOW OOOOoooooOOO. Blood boiling (must be the radiation).
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Mar 28, 2013 17:46
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http://entergy-neworleans.com/content/superbowl/130202_Report.pdf I wonder what other undocumented features S&C relays have. Yeesh.
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Mar 29, 2013 04:10
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slorb posted:http://entergy-neworleans.com/content/superbowl/130202_Report.pdf Hahahahahaha this owns.
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Mar 29, 2013 04:33
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It was either in this forum or another one I frequent when I called this - someone left default settings in the relay and never bothered to adjust them. Massive egg on S&C's face. fake edit: Anti-Hero posted:Woops, looks like someone didn't check the pickup current against expected feeder loading. Hah, close enough.
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Mar 29, 2013 05:34
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My favourite part of the report is at the end where the author references a list of email chains because email chains are where a protection engineer lives and dies.
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Mar 29, 2013 07:18
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Anti-Hero posted:It was either in this forum or another one I frequent when I called this - someone left default settings in the relay and never bothered to adjust them. Massive egg on S&C's face. Is it? To me it seems that they just provided the switchgear. It says they 'assisted' in the coordination study, but it just refers to some email titled 'RE: Superdome'. A utility relying on a manufacturer to come up with relay settings without checking it themselves seems like a horrible idea and a bit un-utility like. Blaming the S&C commissioning technician for not noticing the low settings or advising his customer on protection settings is a nice touch.
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Mar 29, 2013 10:59
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Is blocking current a normal thing on utility systems? I'm just  at the thought of a circuit breaker that won't trip if current is too high and waits for it to come down first. Edit: here's the report's summary for the laymen whose eyes glazed over on page one: Superbowl Report posted:Conclusion: 
grover fucked around with this message at 13:29 on Mar 29, 2013 |
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Mar 29, 2013 12:43
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grover posted:Is blocking current a normal thing on utility systems? I'm just After reading the relay manual it makes sense. It's connected to a switch - not a circuit breaker - so it needs to wait for the current to drop to load levels before tripping (hence the blocking at overcurrent). It's supposed to function as a phase-loss monitoring relay for when a fuse trips, but was acting like a overcurrent relay because of the low settings. e: Now I see why they're blaming S&C. When they put these weird rear end relays in they better set it to the right value, it only depends on fuse size. Knitting Beetles fucked around with this message at 14:03 on Mar 29, 2013 |
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Mar 29, 2013 13:57
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So essentially this was a time delay relay with the caveat of phase protection? - If the current exceeded the trip setting it would initiate a time delay before tripping? - If one phase then went to under 3.5A after exceeding the trip setting it would assume phase loss and trip as well? What was the functionality of the blocking function?
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Mar 29, 2013 16:32
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I think the blocking function is because the relay isn't designed to be safely opened in an extreme overcurrent situation - so it'd be safer to leave it closed and 'ride it out' or wait for the actual overcurrent device (in this case, the 1600A fuses) to open up.
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Mar 29, 2013 17:43
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Cheesemaster200 posted:So essentially this was a time delay relay with the caveat of phase protection? From what I can tell the algorithm was supposed to happen something like this: IF Current > 400A THEN { Wait 2 seconds; IF Current still > 400A THEN { Keep watching; IF Current drops below 3.5A THEN { OH gently caress! FUSE BLEW! FAULT!!!! } ELSEIF Current drops to normal <400A levels { Oh well, was probably just transformer in-rush or something. Reset; } } } And it worked fine like that during the 2nd quarter. During the 3rd quarter, it appears this is what actually happened: IF Current > 400A THEN { Wait 2 seconds; IF Current still > 400A THEN {  } } grover fucked around with this message at 18:02 on Mar 29, 2013 |
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Mar 29, 2013 17:49
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Did they use this thing to avoid having to put in PTs and phase voltage sensing monitor? I am assuming so since it was a fused switch and not a (more expensive) circuit breaker as the primary OCP. I guess the sequence of operations make sense. If you had a phase imbalance relay, you could potentially nuisance trip it depending on how the stadium start up was done. Likewise if you tripped it at any time it went below 3.5A you would get a lot of nuisance trips when the stadium is not in use. Therefore they put in this fancy thing that only trips the motorized switch if the phase current exceeds the fuse rating and then drops below 3.5A. The blocking function just keeps the OCP function in the hands of the fuses. I kind of wonder what the time delay is between an overcurrent situation and a phase loss initiating the trip circuit. In other words, how long does it stay in "waiting" mode per grover's sequence. E: ah, I guess that is the time delay on the relay from what I can deduce. Cheesemaster200 fucked around with this message at 21:44 on Mar 29, 2013 |
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Mar 29, 2013 21:38
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If it was transformer inrush, I'd expect that to be dissipated within, what, no more than ten cycles? Two seconds is an eternity for current flow. IOwnCalculus posted:I think the blocking function is because the relay isn't designed to be safely opened in an extreme overcurrent situation - so it'd be safer to leave it closed and 'ride it out' or wait for the actual overcurrent device (in this case, the 1600A fuses) to open up. The other thing I've seen that sort of thing used is for selective coordination. You have an upstream 1200A main, and there's a downstream 400A breaker. On the circuit off of the 400A breaker there's a 10,000A fault, like a line to line short circuit. It just so happens that the fault occurs on an overlapping point on the trip curves for the main and downstream relays. In that instantaneous trip area. So the downstream relay sends a signal to the upstream breaker saying "Hey, this is in my zone, don't open, I'll interrupt the fault." If the upstream breaker sees 10,000A and no signal, it means there is a fault on the bus, and it must open the main breaker.
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Mar 29, 2013 21:43
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Three-Phase posted:If it was transformer inrush, I'd expect that to be dissipated within, what, no more than ten cycles? Two seconds is an eternity for current flow. This poo poo kills your arc flash levels though and it slows the instantaneous opening time on the trip curves.
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Mar 29, 2013 21:45
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It also reminds of a distribution line sectionalizer. That device can't interrupt fault current. Rather, it has a arming current above a certain amount to remain selective with the upstream recloser, and relies on "counting" the number of reclose operations it detects being committed by the upstream recloser (by counting the amount of times the current drops out) and once a pre-determined of shots have occurred in a window it will open during the last cycle when the recloser has also opened, sectionalizing off the troubled piece of line downstream of it.
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Mar 29, 2013 21:53
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On request from FrozenVent, I'm sharing this photo with the thread. I'm playing Alan Wake and I got told to go start a generator. I found this:  My brain pretty much broke looking at it. The white panel on the right, which I thought would be the gauge cluster, is nothing, and in the game is shaking and emitting smoke. I can't see any actual engine nor generator, and the weird saddle-bag shaped thing seems like an exhaust manifold, but it's shaking like gently caress and doesn't seem to have any trunking and arrggghhhhhh
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Mar 30, 2013 00:46
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Cheesemaster200 posted:This poo poo kills your arc flash levels though and it slows the instantaneous opening time on the trip curves. Yeah, I agree that selective coordination on circuit breakers does nasty things for arc flash (delaying trip time) but the idea here is that you can have the trip levels overlapping and still have coordination to prevent nuisance power outages. Otherwise to prevent nuisance tripping of the main (upstream) breaker from faults that could be cleared by downstream breakers, you'd need to adjust the instantaneous trip curve by adding a time delay so the downstream breaker clears the fault. Crude diagram: code:The only problem here is if you have a fault that somehow breaker 1 isn't able to handle. Then the relay for M goes "Oh poo poo, I'd better trip because breaker 1 somehow didn't interrupt the fault even though it told me he could handle it." Let's face it, circuit breakers period are typically bad for arc flash period. Unless you have systems with arc flash detection trips (optical/sound systems) that can trigger a breaker fast, a maintenance mode that grossly adjusts the trip curve, or the arc-vault system GE has that "moves" the arc flash into a safe compartment. Two Finger posted:On request from FrozenVent, I'm sharing this photo with the thread. Yeah, video games rarely get anything like this right. Even close to right. Three-Phase fucked around with this message at 02:32 on Mar 30, 2013 |
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Mar 30, 2013 02:20
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Pvt Dancer posted:e: Now I see why they're blaming S&C. When they put these weird rear end relays in they better set it to the right value, it only depends on fuse size. Although it is primarily S&C's fault because the manual didn't explain anything, the utility is also to blame because relying on a blocking circuit to prevent load encroachment trips when you aren't forced to to is a bad idea. An undocumented blocking failure mode from the factory isn't usual but leave an electromechanical/electronic relay in service for 40 years of nuisance pickups and eventually the thing might either spuriously trip or not pickup at all. Load blocking to prevent spurious trips does make sense for distance protection relays where you're sending hundreds of MVA down a long transmission line and the load impedance is low enough that it can creep into backup distance zones. In that situation the relay uses the power factor of the fault to discriminate. Fault blocking for coordination when paired with distance protection is occasionally the reason for gigantic blackouts because you're relying on the blocking signal to get to all upstream protection devices and slow them down. If you have the distance protection at transmission substations backing up not just the adjacent subs but ones further away and the person coming up with the scheme misses a weird failure mode or the network gets reconfigured without a proper review you can trip gigantic amounts of load.
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Mar 30, 2013 05:00
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How does the skin effect behave on non-cylindrical conductors? Suppose I have a rectangular bus-bar and start cranking up the frequency. Will the current be forced to the narrow edge as well as outward generally? What kind of wacky current distribution would an I-beam have? Does it matter much so long as the wavelength is long relative to the cross-section of the conductor? On the Superdome thing, it's a hidden feature that relays will trip when exposed to sustained current above their set-point?  From the description of the relay, it sounds well-documented and straightforward:1: Relay conducts and all is well 2: Current exceeds setpoint, timer starts 2.5: If current drops below setpoint and is above 3.5 A, timer expires uneventfully 3: If current is above 600 A, relay remains closed and declines the opportunity to self-destructively open 3.5: If timer expires and current is still above setpoint but below 600 A, 4: If current drops below 3.5 A while the timer is running, If anything, the weird feature to me is that a setpoint above 600 A will cause the relay to only trip on the low-current condition.
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Apr 3, 2013 17:37
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Frozen Horse posted:How does the skin effect behave on non-cylindrical conductors? Suppose I have a rectangular bus-bar and start cranking up the frequency. Will the current be forced to the narrow edge as well as outward generally? What kind of wacky current distribution would an I-beam have? Does it matter much so long as the wavelength is long relative to the cross-section of the conductor? For 50/60 Hz the skin depth is about an inch, giving a round conductor a maximum carrying capacity of about 2000 Amps. Non cylindrical conductors are generally better because they have a larger surface area and the average 'depth' of the conductor is smaller. There's a catch: because at sharp edges electrons are bunched together more than on a round surface, the e-field is a lot larger. To prevent flashover you would need more insulation / spacing to other conductors or ground. For low voltage this doesn't matter that much which is why you see rectangular conductors there, cheap to make and still a lot better than round ones. For higher voltages an I-beam is a good conductor shape actually, just have to round off the outer edges so you can still put them close together.
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Apr 3, 2013 18:15
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Wide, flat conductors exhibit less inductance, as well, iirc. This isn't significant at 50/60Hz unless you're talking about a LOT of conductors, or a LOT of amps, but it becomes pretty important when you're working on high power RF equipment. That's why you'll generally see grounding (and in some cases RF signal wiring) done in transmitters with stacks of thick copper foil or strips instead of round conductors. Hell, it's easy to stamp out flat copper straps from a roll of sheet stock, so it can be good for extremely high current AC/DC power distribution that has to handle flexure/vibration as well. It's also very significant when designing lightning damage prevention stuff - lightning rods, etc really really need a VERY low impedance bonding conductor to a very good grounding network, due to that whole "very sudden billion-amp current surge" thing. edit: many high power transformers for AC distribution systems are wound from flat copper or aluminum strap rather than round conductor as well, especially on the lower voltage, higher current winding. https://www.youtube.com/watch?v=tUO3o5JTGhQ kastein fucked around with this message at 19:17 on Apr 3, 2013 |
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Apr 3, 2013 19:14
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I've seen substations and installations like HVDC "valve halls" that use what looks like aluminum tubing. I think with an I-beam my concern would be corona discharge at the sharp edges if we're talking hundreds of KV.
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Apr 3, 2013 23:27
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Anyone proficient in SKM here? I have a five section 4160V ring bus fed from five paralleled transformers of equal impedance and size. Loads are out of balance to a degree on some busses versus others, but nothing that major. The bus itself can handle the full load amps of four of the transformers. I put this all into SKM, but for some reason the section 4 transformer will not accept any load and dumps it all onto section five, overloading it. If I isolate section 4 it works peachy, but refuses to accept load when I close the tie. In fact, when I do that the another transformer on the ring bus just disappears. I want to do a load flow analysis, but this crap is making me bonkers. It just does what it wants!
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Apr 11, 2013 22:26
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