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Didn't see this until recently: ABB Develops 1.2MV Circuit Breaker 1200kV Dead Tank Breaker Wow. The end connector has five separate corona rings.   
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May 12, 2012 00:49
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Three-Phase posted:Didn't see this until recently: 5 corona rings is a bit insane!
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May 12, 2012 12:26
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A guy claims to have made a DIY Tesla gun: http://www.theverge.com/2012/5/13/3017796/diy-tesla-gun-rob-flickenger Would this even work? Wouldn't it just ground through the easiest path, which could very well be the operator? Edit: Don't bother with the video, it doesn't demonstrate it.
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May 13, 2012 23:10
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ruro posted:A guy claims to have made a DIY Tesla gun: http://www.theverge.com/2012/5/13/3017796/diy-tesla-gun-rob-flickenger This site has diagrams on tesla coils: http://www.richieburnett.co.uk/operation.html It looks like it's really just a Tesla coil that's portable. That ground connection does not need to be a physical earth, it could basically just be connecting the center tap of the HV transformer to the ground of the secondary coil. The biggest hazards would probably be internal. My guess is the battery drives a small inverter (DC to AC), and then the AC is run through a neon sign transformer or similar device to get HV out. The problem there is that the HV would probably be current limited, but still very hazardous. As far as the HV coil output, the problem there is that the frequency is so high the body doesn't detect that energy. However it can still cause "RF burns". If you "shoot" someone with if, I doubt you're going to kill them. If you build it shoddily or play with the step-up transformer, that could be dangerous. Three-Phase fucked around with this message at 23:26 on May 13, 2012 |
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May 13, 2012 23:21
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My buddy The Proc suggested I cross-post this here from my thread. Maybe you could offer some advice on whether this is reasonable! Here's what I (occasionally) work with:  I know I'm big on saving lives and all that, but sometimes our health & safety unit goes overboard. I got an email this afternoon that says we're going to need special protective equipment from now on if we go into a signal cabinet, even if we're just looking over the flashing lights or changing phase timings. Note that signal cabinets have significantly better wiring and grounding than the circuit breakers in almost any house, and they're 120 VAC max. So, what kind of safety equipment are we talking?  This arc flash suit (we're leasing them, so I won't get to attach my own cool decals) PLUS a retroreflective hard hat PLUS safety glasses underneath PLUS a type III retroreflective shirt PLUS heavy gloves PLUS insulated steel-toed boots. It's going to be a lot of fun in Summer, especially if you're the third guy to wear it that day. You didn't think we'd each be getting our own, did you? There is a silver lining, though: I am going to pull SO many pranks in that suit, like frantically waving at drivers from atop an overpass, and going to restaurants all dolled up like that.
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May 16, 2012 00:47
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Cichlidae posted:So, what kind of safety equipment are we talking? For the actual regs, check out NFPA-70E. The rules vary depending on what you're doing and the arc fault potential. You need one level to open the door, another if you're standing 3' back when someone else opens it, something else if you're connecting equipment, and the worst-case only if you're actively grabbing and working with energized conductors. grover fucked around with this message at 01:04 on May 16, 2012 |
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May 16, 2012 00:57
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I would be very surprised if that was anything over Level 0. And now for something completely different: Switchgear and cool jazz Removing links LIVE at 138kV Three-Phase fucked around with this message at 01:41 on May 16, 2012 |
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May 16, 2012 01:23
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Looking at the equipment (signal cabinet), you'd probably be at a category 0 most of the time, possibly category 1 if you're exposing yourself to live conductors. This is with the assumption that the available fault current is under 25kA and the upstream protective device will clear in two cycles. When in doubt, have someone do a study.
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May 16, 2012 01:30
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I was talking to a guy at work about PPE requirements. He told me that NFPA 70E only applied to facility wiring, not to appliance wiring (i.e. anything with a UL sticker on it). I know this guy will make stuff up just to show how "smart" he is. Is basis in reality for this?
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May 16, 2012 01:37
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Guy Axlerod posted:I was talking to a guy at work about PPE requirements. He told me that NFPA 70E only applied to facility wiring, not to appliance wiring (i.e. anything with a UL sticker on it). Are you talking about equipment that would be directly wired into an electrical system at a lower voltage (<600V) that still bears the UL sticker? Are you wiring up live, or testing live equipment with protective covers removed? Three-Phase fucked around with this message at 01:54 on May 16, 2012 |
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May 16, 2012 01:48
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I don't really know much about electricity, but that live link removal video 
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May 16, 2012 21:08
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So does anyone know about arc fault (AFCI) breakers? I just bought a new house and it came with arc fault breakers, which so far I've had to get 3 of them replaced with regular breakers because they kept tripping during normal operation. My electrician claims that they kind of suck. He says he puts them in there to start with because it's what inspectors like to see, but usually he'll end up having to come back out and replace some of them because they trip when they're not supposed to. Is he full of poo poo?
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May 16, 2012 21:49
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the nicker posted:So does anyone know about arc fault (AFCI) breakers? If he suspects a bad AFCI, swap it out with another. Test with known good power sources, like simple lamps. If it trips when you plug a lamp it, it's most likely a ground-neutral fault. grover fucked around with this message at 22:00 on May 16, 2012 |
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May 16, 2012 21:58
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Yeah, in short replacing a properly installed, post 2005-ish AFCI that trips with a regular breaker is sort-of like taking a piece of electrical tape and putting it over the "CHECK ENGINE" light on your car. Except the car will probably not catch on fire and destroy your house or kill you/your family in your sleep.
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May 16, 2012 22:23
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Captain Foo posted:I don't really know much about electricity, but that live link removal video HIS FACE at 3:27. In his brain it's either: "This is stupid, we're going to die. I'm going to die." Or: "Dammit I'm going to miss Eurovision if this takes more than an hour. poo poo." That 132kV bus probably feeds something really important. Like the biggest googly-eye plant in Germany. That's a load they just can not afford to shutdown! Three-Phase fucked around with this message at 22:31 on May 16, 2012 |
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May 16, 2012 22:29
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Three-Phase posted:Are you talking about equipment that would be directly wired into an electrical system at a lower voltage (<600V) that still bears the UL sticker? Are you wiring up live, or testing live equipment with protective covers removed? This is 480 VAC equipment, testing operation and verifying input voltage, etc. Also, whoever decided to put 24V, 120V, and 480V all in the same cabinet in this equipment was a moron. They probably also got a pat on the back for saving the company money.
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May 16, 2012 22:42
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Guy Axlerod posted:Also, whoever decided to put 24V, 120V, and 480V all in the same cabinet in this equipment was a moron. They probably also got a pat on the back for saving the company money. Could be worse. (24VDC, 120VAC, 600VAC, 600VDC)
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May 16, 2012 22:48
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grover posted:Your new house is probably full of wiring errors, no doubt due to your electrician miswiring poo poo. They should NOT be tripping during normal use, and it's illegal to remove required AFCIs and replace them with normal breakers. Tell him to fix the loving wiring faults or you'll report him to the city and have his license revoked. Is there anything I can check myself to verify this before calling them back and accusing them of being idiots? I did of course have the house inspected and the electrical passed without issue. He tested the ground at every outlet and also poked around inside the breaker box. The first one would trip randomly when I had my entertainment system going (tv, receiver, cable box, ps3 etc). The second one would trip if I flipped on the flood lights at night (2 sets of motion-sensing floods with 2 150-watt bulbs each). The third was in the kitchen and would flip if I plugged the vacuum into one of the outlets (vacuum worked fine in any other area of the house). What specifically could cause that? Other than a faulty AFCI, but seems weird that 3 out of 8 or so would be bad right out of the box. edit: Come to think of it, the three AFCI breakers that were tripping were all for circuits that also had GFCI outlets. The kitchen, guest bath (same circuit that my entertainment wall is on), and master bath (i remember them telling me that the flood lights in the back were also on the GFCI circuit in the master bath). Coincidence? I'll verify that when I get home. However in each case it was the AFCI in the breaker box that was tripping, I've never had a GFCI outlet trip. CheddarGoblin fucked around with this message at 17:12 on May 17, 2012 |
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May 17, 2012 16:59
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the nicker posted:Is there anything I can check myself to verify this before calling them back and accusing them of being idiots? I did of course have the house inspected and the electrical passed without issue. He tested the ground at every outlet and also poked around inside the breaker box. You could swap a known good AFCI with one that's tripping and see if the "good" one starts tripping and the "bad" one suddenly works fine. That's always a good indication of an issue in the circuit. You could also disconnect the ground wire from the panel and see if there is still continuity with the neutral- that's always a good sign of a "he done hosed up".
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May 17, 2012 22:41
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Three-Phase posted:Removing links LIVE at 138kV That arcing, is that from just the capacitance of the link and breaker?
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May 18, 2012 15:27
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grover posted:Sounds to me like the electrician done hosed up somewhere. Whether the GFCI or the AFCI would trip would depend where the wiring fault is. Cool, thanks. I can do that. I've already reported the problem to the builder (the house is under warranty), but I'll do the ground/neutral continuity test before the electrician comes back out. That way, if I find that there's a problem and the electrician tells me everything is fine, I can call him on his bluff. Also I was wrong about it only being on the circuits with the GFCI outlets. Another weird thing I've noticed is that it looks like multiple people worked on the wiring. I've opened up 3 of the switch boxes to install timer switches for the bathroom/laundry exhaust fans, and noticed that they're all wired differently. In some boxes, the ground is hoooked up to each switch and in others it's not. Also, in some the wires are completely looped around the terminal screws on the switch, and in some they're straight.
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May 18, 2012 19:18
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Frozen Horse posted:That arcing, is that from just the capacitance of the link and breaker? Yeah. Just capacitance to ground. It's something important to consider in delta systems. Ideally, the delta has absolutely no reference to ground. However, due to capacitance, there is a (albeit poor) reference to ground. grover posted:You could swap a known good AFCI with one that's tripping and see if the "good" one starts tripping and the "bad" one suddenly works fine. That's always a good indication of an issue in the circuit. You could also disconnect the ground wire from the panel and see if there is still continuity with the neutral- that's always a good sign of a "he done hosed up". That "switch components out" trick typically works to eliminate the number of possible problem causes. We're probably going to do that next week at work. Except the breaker that might be "bad" is as big as a washing machine (7200V, 1200A). The problem may be one of the poles is slow to close or bouncing, causing single-phasing where for a "more than brief" moment only two of the three phases are conducting. You hear the breaker slam closed, this brief "groaning" noise, and then the breaker trips free within a fraction of a second. Working with this stuff you get a feel for what sounds are normal and what sounds aren't, and it's actually a surprisingly important sense. As an aside, I was surprised that a YouTube search for "Breaker Pole Closing" results in, among other things, a Wu-Tang Clan song. Three-Phase fucked around with this message at 21:51 on May 20, 2012 |
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May 18, 2012 23:31
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Is there enough power flowing through lines at street level to cause corona discharge on a really humid day?
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May 30, 2012 01:49
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GWBBQ posted:Is there enough power flowing through lines at street level to cause corona discharge on a really humid day? I think the corona discharge has more to do with voltage than power flow (correct me if I'm wrong here). I doubt you'd see it on a normal overhead (like 13kV) power line. Maybe on a larger piece of equipment. If you go near a substation, you may see what looks like metal "halos" or toroids suspended near where connections are made between components. Those create a smoother potential gradient around the equipment. If you have a very sharp point with a high voltage on it, you can generate a corona there. I've heard people say they've seen glow, and it has been photographed using timed exposure, but I think you'd never be able to see it during the day. Also, in a system you want to avoid corona discharge. It causes interference, can damage insulation, and generate Ozone. Three-Phase fucked around with this message at 02:16 on May 30, 2012 |
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May 30, 2012 01:54
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I've only seen the corona at a 500kV sub after a good rain on a very humid day. Even then it was pretty faint, but still cool to see (and hear).
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May 30, 2012 18:08
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SeaBass posted:I've only seen the corona at a 500kV sub after a good rain on a very humid day. Even then it was pretty faint, but still cool to see (and hear). I was walking under lines (I think about 345kV) on a warm, humid day and I couldn't see but I could clearly hear the buzzing from the corona. Check it out: corona cam: https://www.youtube.com/watch?v=OFI3Ielbyx8
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May 31, 2012 01:21
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SeaBass posted:I've only seen the corona at a 500kV sub after a good rain on a very humid day. Even then it was pretty faint, but still cool to see (and hear). Wow, I just found a video of 500kV corona at a substation! It's beautiful! https://www.youtube.com/watch?v=qNTdBVg35-Y
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Jun 2, 2012 22:07
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Three-Phase posted:Wow, I just found a video of 500kV corona at a substation! It's beautiful! Yep, that's pretty much what we saw.
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Jun 2, 2012 23:10
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They really should have put a ring on it.
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Jun 3, 2012 05:49
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Three-Phase posted:I was walking under lines (I think about 345kV) on a warm, humid day and I couldn't see but I could clearly hear the buzzing from the corona. I used to live under some high tension lines that ran through the middle of an apartment complex; the buzzing on a humid night was really something. Also fun to walk out there with a florescent light bulb and freak out the neighbors. Why yes, this was a very low rent/ghetto complex, how did you know?
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Jun 4, 2012 00:59
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some texas redneck posted:Why yes, this was a very low rent/ghetto complex, how did you know? Not to get too political, but I've been told this is why you see cancer clusters under power lines: Power lines and substations are NIMBY - Not In My BackYard. The land values under there drop like a rock. People with less money live there, and unfortunately there are some medical conditions, like cancer, that you're statistically more susceptible to by being in a lower tax bracket.
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Jun 4, 2012 01:20
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Three-Phase posted:I think the corona discharge has more to do with voltage than power flow (correct me if I'm wrong here). I doubt you'd see it on a normal overhead (like 13kV) power line. Maybe on a larger piece of equipment. Three-Phase posted:Wow, I just found a video of 500kV corona at a substation! It's beautiful! Three-Phase posted:Not to get too political, but I've been told this is why you see cancer clusters under power lines:
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Jun 5, 2012 02:53
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GWBBQ posted:So any buzzing caused on street lines is probably from a transformer? Buzzing does not necessarily mean there's corona. When I did transformer testing, when you had a lot of power running through a transformer (couple hundred KVA 4160 to some lower voltage) you could hear it vibrate as more current moved through it.
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Jun 6, 2012 01:32
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GWBBQ posted:So any buzzing caused on street lines is probably from a transformer? Depends on the hum. A 60hz hum (very low hum) is the result of sticking a lot of AC down a wire - it induces an alternating magnetic field, which rags the conductor towards and away from any other current in the vicinity. Transformers are particularly susceptible, as they're effectively a pair of drat great electromagnets, but the wiring in your walls can generate it too. If it's not a low hum but a crackling, that's corona discharge. coffeetable fucked around with this message at 13:09 on Jun 6, 2012 |
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Jun 6, 2012 13:06
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I got a new position out of the office as a project engineer at a mill. There's some serious power there, a line-up of 8 ball mills and two rod mill that are 2000hp each. There's also a SAG mill that's run by two 5500hp motors, and this is all in the grinding aisle, still plenty more of the plant to check out. I haven't had time to check out the type of starters or the voltage their running at, but it's all pretty cool stuff. The place was constructed between 1940-1960 and there's a huge amount of upgrades it's going through and I'm hoping there's a lot of electrical ones. Right now I'm working on projects to upgrade this plant plus another two smaller ones to Allen-Bradley Flex I/Os from the outdated PROVOX DCS and PLC5s. Not as cool as high voltage but it's a pretty large project regardless.
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Jun 6, 2012 22:44
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I'd be interested in hearing about what you have. At 5000HP you could have synchronous or induction motors. I'm guessing no less than 2400V (for 5000HP 2.4kV may mean parallel cables), maybe 4160V or 7200V? It's been interesting to see the evolution from the most primitive PLCs (replacement for cabinets full of relay logic) to more robust control systems (adding analog I/O, PID loops) to networking (Fieldbus, PROFIBUS, DeviceNET) to the most modern systems (Ethernet, Wireless, Remote/IO and Distributed Control). BONUS! MV SWITCHGEAR FROM MERLIN GERIN! Photo from Schneider Electric  This is some of the weirdest looking gear I think I've ever seen.
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Jun 7, 2012 01:23
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Three-Phase posted:BONUS! MV SWITCHGEAR FROM MERLIN GERIN! One of Schneider Electric's regional headquarters (of a multi-national overseas region I'll not name) is literally in a house, as in a housing development mcmansion in the middle of a residential suburb, with normal homes on all sides. Apparently, zoning laws are lax in that country and it was cheaper than an office building. Even has a garage to do the work in right on-site! grover fucked around with this message at 02:36 on Jun 7, 2012 |
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Jun 7, 2012 02:33
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Three-Phase posted:I'd be interested in hearing about what you have. At 5000HP you could have synchronous or induction motors. I'm guessing no less than 2400V (for 5000HP 2.4kV may mean parallel cables), maybe 4160V or 7200V? In most of the mills I've worked at (steel or aluminum), the main motors (5-10MW range) were either 3300V or 4160V, depending on whose drives were being used. Of course, I've never seen a motor that big on a starter, since everything I've seen has required fairly precise speed control for process reasons. Parallel cables are almost always used on a motor of this size, IME.
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Jun 7, 2012 14:12
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KaiserBen posted:In most of the mills I've worked at (steel or aluminum), the main motors (5-10MW range) were either 3300V or 4160V, depending on whose drives were being used. Of course, I've never seen a motor that big on a starter, since everything I've seen has required fairly precise speed control for process reasons. 10MW at 4160V is a hell of a lot of current. 1300A would definitely require parallel cable connections like 4 per phase. What was the inrush for a motor like that starting across the line? 10kA? I've seen some motors that were above 4160V to 13800V that used a single triplex HV cable, like 15kV Okogaurd shielded cable. 500kcmil at 13.8kV, unity power factor, in a cable tray at 105C, we're talking about 12MW in a single (albiet rather large and heavy) cable tray cable. Moving them about is a challenge, and you need to connect them to busses very carefully. 500 feet of the 500kcmil triplex stuff weighs nearly two tons. We had a parallel 500kcmil run (2 x triplex, six conductors total) and the spool that it came in on was more than ten feet in diameter. We treated that spool with immense respect because of how much it weighed.
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Jun 8, 2012 02:17
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Three-Phase posted:10MW at 4160V is a hell of a lot of current. 1300A would definitely require parallel cable connections like 4 per phase. What was the inrush for a motor like that starting across the line? 10kA? Yeah, they usually used 6 cables, not 100% sure, but they were 500kcm range. The inrush was limited by the drive, we try not to start such things across the line, for obvious reasons. Even on a VFD, it routinely pulled 300% current (for <one minute, as per the overload capability) as a slab went through the mill. I'd honestly have to check for the currents, we almost always deal in terms of per unit power/percentages, so raw amps generally have to be calculated. I'm on a much less exciting (power-wise) project now, automating container cranes; lots of cool automation equipment (laser measurement scanners especially), but the power requirements are pretty small (1MW per crane or so, 5-6 for the ship-to-shore cranes). Each crane is fed from an 11kV cable trailing behind it that gets wound up on a reel as it moves down the track. Interesting stuff, but I prefer the steel industry overall.
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Jun 8, 2012 08:14
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