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Remember how I said my company did some testing at an NSA datacenter? Yeah, about that... Surprisingly I actually hadn't heard that these kind of issues were coming up. One of our guys that worked there did severely injure his hands during an arc flash event...because he tried to check a medium-voltage switch dead with a low-voltage contact meter. 
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Oct 9, 2013 02:33
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An arc fault caused by employee error would be thoroughly investigated immediately. There's no way the error would be repeated numerous times. It's almost certainly equipment related. There's a small chance it's caused by improper clearance distance from energized parts, but a government facility is going to be well constructed with plenty of oversight. Scratch that. Arc flashes are common in aging substations due to leakage current from degrading insulators, but that's unlikely here given the age of the facility and its importance. Scratch that too. My guess is that the something was not built to insulate the peak voltage it is seeing, or not beefy enough to handle the kind of amperage it is seeing. Perhaps the NSA is being too secretive for its own good?
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Oct 9, 2013 02:38
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I think I might have found the problem...arstechnica posted:The Army Corps of Engineers is overseeing construction and promised to make sure the data center is "completely reliable" before allowing it to go online.
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Oct 9, 2013 02:53
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Noctone posted:One of our guys that worked there did severely injure his hands during an arc flash event...because he tried to check a medium-voltage switch dead with a low-voltage contact meter. There was a YouTube video about a guy at a plant who was checking a 2400V motor starter using a regular low-voltage multimeter. The theory was he absentmindedly mistook it for a 480V starter somehow. The instant he touched the voltmeter leads on the A-line and B-load side of the fuses, the meter exploded and cause an arc flash in the breaker. He was blown across the isle and slammed into the gear several feet away. He eventually made it to an office to get first aid, but he left a trail of burned clothing and melted tools in his wake. He was conscious and muttered "I messed up". He later died in the hospital from the severe burns. The cubicle and breaker were destroyed in the incident. It's still part of the 2400V lineup, but the equipment was removed and there's a memorial plaque bolted on the cubicle door.  Charlie Morecraft spoke where I worked several years ago. He wasn't in an arc flash but a fire at a refinery. You could hear a pin drop in the auditorium when he was speaking and explaining all the stuff that happens when you get third-degree burns. You had big, tough guys who were cowering when he talked about things like skin debridement.
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Oct 9, 2013 14:25
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babyeatingpsychopath posted:In most suburbs, there's only one phase per street. The subdivision will have 3-phase run by it, and only one phase will go down each street.
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Oct 9, 2013 14:52
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Three-Phase posted:There was a YouTube video about a guy at a plant who was checking a 2400V motor starter using a regular low-voltage multimeter. The theory was he absentmindedly mistook it for a 480V starter somehow. The instant he touched the voltmeter leads on the A-line and B-load side of the fuses, the meter exploded and cause an arc flash in the breaker. He was blown across the isle and slammed into the gear several feet away. He eventually made it to an office to get first aid, but he left a trail of burned clothing and melted tools in his wake. He was conscious and muttered "I messed up". He later died in the hospital from the severe burns. Yeah I was really surprised when I heard about it, he didn't have any scars or lack of functionality that I could see. Lucky bastard if there ever was one. I asked one of my coworkers that spent a lot of time at the NSA datacenter what the deal is with the arc flash incidents, but he didn't really know anything either.
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Oct 9, 2013 15:45
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drk posted:Unfortunately the article Ars is citing at the Wall St Journal is paywalled, so its not clear if anyone was injured. Say what you will about the NSA, but I also hope no one got injured. It could be a capacity problem, it could be lovely operators, it could be a poorly designed facility but most likely it is a combination of all of the above.
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Oct 9, 2013 19:17
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SeaBass posted:It could be a capacity problem, it could be lovely operators, it could be a poorly designed facility but most likely it is a combination of all of the above. It's probably just that, but I'm going to hope that it's really sabotage.
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Oct 9, 2013 19:26
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IOwnCalculus posted:It's probably just that, but I'm going to hope that it's really sabotage. Yeah, that would be a lot cooler than them just being morons.
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Oct 9, 2013 19:30
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SeaBass posted:Yeah, that would be a lot cooler than them just being morons. Not mutually exclusive, at least!
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Oct 9, 2013 20:48
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GWBBQ posted:Depends on your neighborhood. A lot of neighborhoods in my area have three phase primaries because there are water pumping stations that need it, and I'm sure the local power companies would be happy to gouge you on a higher rate. You might need a commercial account, but it's easy enough to incorporate if they require it. What do you think that would do to homeowner's insurance rates?
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Oct 10, 2013 03:10
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It's burgin' time! 
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I heart bacon posted:What do you think that would do to homeowner's insurance rates?
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Oct 10, 2013 03:39
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GWBBQ posted:My policy was written by someone nitpicky enough to explicitly exclude damage caused by asteroids or space debris, so I'm going to guess my premiums would increase substantially. Either that or they would also force you to switch to a commercial policy. My last renters insurance policy covered space debris, unless it was powered by a nuclear reactor or RTG.
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Oct 10, 2013 14:41
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I could see this as a great candid camera stunt: nice old lady calls about a problem with a breaker tripping. The electrician comes over, goes to the basement, and there's a huge 4160V gear lineup in the basement.
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Oct 10, 2013 22:15
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MrYenko posted:My last renters insurance policy covered space debris, unless it was powered by a nuclear reactor or RTG. Ha! My rental policy covers nuclear events not part of an act of terrorism. However, it specifically excludes fires resulting from acts of war. Policy writers must have an awesome job sometimes.
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Oct 12, 2013 20:31
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I have a really weird question about humming during an electrical storm... I live about a mile and a half from a major substation and incredibly close to major utility easements that traverse the town north/south. Last night we had a particularly bad thunderstorm that knocked out power to ~7000 residents. My power went out for around 20 seconds and the map showed most of my neighbors in a major outage area. For the next 2-3 hours I heard an intermittent humming noise at 120Hz that coincided with major lightning flashes in the clouds above. It definitely wasn't inside the house and was incredibly pronounced when I went outside but I wasn't walking around in the rain to find out where. It's definitely one of the weirder things I've noticed electricity-wise and was wondering if any of the experts in this thread could weigh in with a possible explanation. TX297 fucked around with this message at 00:09 on Oct 14, 2013 |
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Oct 13, 2013 21:01
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I heard y'all like old electrical gear. I went to the historic mining park in Tonopah, NV: Operations Stopped by atomicthumbs, on Flickr That red building contains the hoist controls, motors, flat cable winch, and huge air compressors. I took some photos of the electrical bits with this thread in mind.  Motor starter, I think.  Westinghouse motor dataplate. I don't think "Patented '97" means 1997.   Switchgear and back of said switchgear.      Big ol' motors with big ol' windings and big ol' commutators (?) And, finally, the pinnacle of motor speed control technology ca. late 1800s/early 1900s: a big loving bank of resistors (data plates said "rheostats"). I'd hate to be the one on the winch controls standing right next to them. Note the little control podium with the cables and handle in the last picture.    
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Oct 14, 2013 03:05
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Early industrial electrical poo poo is all so  It's also so, basic, just fundamental applied electrical theory without no covers or control boards to mask it. You can look at every piece in there and make a pretty educated guess at what it is, just because there's so little hidden. Amazing how we got from open air transfer switches to having to wear PPE just to reset a modern 20A circuit breaker.
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Oct 14, 2013 12:14
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grover posted:Early industrial electrical poo poo is all so "Jones is dead! He bumped against an exposed electrical switch." I wonder if that's a wound-rotor induction motor. http://en.wikipedia.org/wiki/Wound_rotor_motor Three-Phase fucked around with this message at 01:44 on Oct 15, 2013 |
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Oct 15, 2013 01:40
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Protection against the tragic dangers of the open knife switch! Which were banned by code, effective Jan 1st, 1921, apparently.
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Oct 15, 2013 01:44
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I'd bet on those resistor banks being for braking actually, not speed control. Something like the gigantic resistor banks and cooling fans in a diesel locomotive.
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Oct 15, 2013 02:09
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kastein posted:I'd bet on those resistor banks being for braking actually, not speed control. Something like the gigantic resistor banks and cooling fans in a diesel locomotive. It really looks like a wound rotor motor; they're still used quite commonly in mining equipment, especially ore crushers (with VFDs now used in place of the speed control resistors). The three slip rings are a dead giveaway, synchronous motors would only have 2. The big switch looks like it could be for switching resistances, and thus speeds. It appears to be wired to various combinations of resistors, and that resistor bank is quite oversized for braking.
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Oct 15, 2013 03:35
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grover posted:Amazing how we got from open air transfer switches to having to wear PPE just to reset a modern 20A circuit breaker. Do people in the US actually wear PPE for switching MCBs? I do arc flash assessments in Europe mostly and it's always a good laugh when I tell workers that this in their corporate safety policy. I try to hammer on doing risk assessments as well (requirement of NFPA 70E no less) to get better acceptance but the US safety people always recoil at the though initially. Really, what?
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Oct 15, 2013 04:44
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I think he was being intentionally hyperbolic. Very rarely will you find a 20A breaker in a panel/switchboard that merits even an HRC 2. In a general sense, sure as poo poo people wear PPE for switching molded case circuit breakers (as well they should).
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Oct 15, 2013 05:13
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For what reason? A 20A MCB breaking apart and causing an arc?
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Oct 15, 2013 06:12
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You do arc flash assessments for a living and you're asking this? 
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Oct 15, 2013 06:15
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Why not? Wearing PPE for something with neglible risk is doing it wrong.
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Oct 15, 2013 06:46
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Pvt Dancer posted:Do people in the US actually wear PPE for switching MCBs? I do arc flash assessments in Europe mostly and it's always a good laugh when I tell workers that this in their corporate safety policy. I try to hammer on doing risk assessments as well (requirement of NFPA 70E no less) to get better acceptance but the US safety people always recoil at the though initially. Really, what? Nobody suits up to reset a 20A breaker, ever, though. Don't know why that poo poo's even on the books.
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Oct 15, 2013 10:56
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grover posted:Real answer? Depends who's watching. The problem with that kind of stuff though is that it creates an environment where it's "ok" to bypass procedure when they're not, in the opinion of the worker, justified. It attacks the credibility of the procedure or safety management plan, if you will, and it's how you end up with people smoking under No Smoking signs, working cranes without a hard hat or going down a 50 ft ladder without an arrestor because "I'll just be down there a minute". It's lazy corporate safety management ("Oh, let's just blanket require everyone to wear all the PPE, all the time!"), and it's a terrible practice.
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Oct 15, 2013 14:08
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Pvt Dancer posted:Why not? Wearing PPE for something with neglible risk is doing it wrong. Well first of all I said in general, because molded case circuit breakers do cover quite a range. But, yes, there are situations where it's definitely a good idea to wear PPE to do switching on a 20A breaker. 120/208 panelboard? Probably not, as I mentioned before. 480 or greater? Lot more likely. A tripped feeder breaker on a switchboard with a high available fault current is a closed-casket funeral waiting to happen.
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Oct 15, 2013 14:53
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No contest that there are situations where arc flash PPE is needed regardless of the size of breakers, it's just so weird to see how common it is to completely ignore the circumstances. Maybe it's because the companies I work with usually had a bad accident prompting them to also do arc flash assessments outside the US and want to be super careful. But the blanket requirement of PPE all the time when working inside the arc flash boundary just leads to people thinking it's nonsense, making their own judgement calls and end up not wearing anything when doing the actual dangerous work.
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Oct 15, 2013 15:22
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Ohhhhhh I see what you've been getting at. Yeah, I've definitely heard of places that require PPE for any and all switching regardless of the actual hazard and/or risk. It's dumb and leads to exactly what you mentioned.
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Oct 15, 2013 16:13
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I just toured a supercomputer and got to see the power and cooling stuff too. The capacity of the building is 24 megawatts. Crazy stuff.
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Oct 16, 2013 00:19
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From my experience: Operating small MCC in a closed panel: no PPE Operating MCC breaker (>100A or so): no PPE, but stand to the side and operate the switch Taking the cover off a live panel: PPE (generally level 2) Racking large breakers in live: No PPE (work performed using a remote racking robot, operator well outside the boundary areas) Manual trip of large breakers (via "trip hole" in the cover): Not sure. This is a scary area. Probably erring on the side of "yes". I don't even want to stand around the equipment when it's closing or opening. (One of my mentors told me that on some gear, the back side where the bus is covered is just as or more dangerous than the front.) squeakygeek posted:I just toured a supercomputer and got to see the power and cooling stuff too. The capacity of the building is 24 megawatts. Crazy stuff. I saw an old Cray setup that required a motor-generator set to provide a 400hz three-phase power supply. Good way to provide fairly clean power and isolate the computer from transients. I do have a question about modern CNC routers and other machining equipment: if you have a serious power problem (brownout/blackout) are modern machining systems able to resume where they left off? I've heard of some high-end systems having small integral UPS units, so if something bad happens they can bring the system to a safe state, re-initialize, and continue where they left off. Putting an entire machine on UPS, unless you're doing something like doing semiconductor fabrication, seems incredibly expensive. The problem is if you're machining something out of a block of aluminum or titanium, there's a power glitch, and that incredibly expensive part you're working on has to be thrown out. Three-Phase fucked around with this message at 01:28 on Oct 16, 2013 |
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Oct 16, 2013 01:23
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Three-Phase posted:I do have a question about modern CNC routers and other machining equipment: if you have a serious power problem (brownout/blackout) are modern machining systems able to resume where they left off? I've heard of some high-end systems having small integral UPS units, so if something bad happens they can bring the system to a safe state, re-initialize, and continue where they left off. Putting an entire machine on UPS, unless you're doing something like doing semiconductor fabrication, seems incredibly expensive. I'm not aware of any machines that can restart right where they left off. After a power down (intentional or not), the machines need to be 'homed out' so the control knows where the axes are positioned. CNC programs can be changed to pick up where the cycle was interrupted, but unless I'm totally out of the loop, you can't just turn a machine on and start cutting from the middle of a shutdown. As you say, chances are the tooling or part are broken anyway, depending on how graceful the machine stops on loss of power. That's what good welders are for! Then again, what are those high end systems you've heard of? I'm intrigued.
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Oct 16, 2013 01:51
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I'd imagine you must have to. Some parts take days to machine. You can do damage to a part if the spindle were to just spin down on its own, like if you are tapping threads, or if the axes aren't held in place without power, and they just drop.
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Oct 16, 2013 01:53
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60 Hertz Jig posted:Then again, what are those high end systems you've heard of? I'm intrigued. I am starting to think that the comments I heard about systems that had an integral UPS might have been erroneous. I didn't stop to consider things like drills and taps getting hung up in a power-loss event.
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Oct 16, 2013 10:24
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Three-Phase posted:I am starting to think that the comments I heard about systems that had an integral UPS might have been erroneous. I didn't stop to consider things like drills and taps getting hung up in a power-loss event. Maybe it would store enough power to safely stop machine movement and gracefully shut down? The tools might still be screwed but if it keeps the machine from crashing it would be very useful. The machines I run have a 'power fail detection circuit'.. whatever that entails. All I know is we do lose power every now and then and our machines haven't blown themselves to bits yet.
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Oct 16, 2013 17:30
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There are UPS for every application; you can get them in multiple megawatt arrays. If it's an important enough process or interruption would result in a lot of damage or financial loss, you can put an UPS in. Run-time depends on how large the batteries are, but it's easy to size batteries to give enough time for generators to start up and pick up the load. Or if the UPS would cost $3M and a power failure "only" ruins a few thousand dollars worth of parts each time, could be cheaper just to let it fail. My favorite, though, are superconducting electromagnetic energy storage. Literally a coil of superconducting wire sitting in a tank of cryogenic helium that can dump out a SHITLOAD of power in a fraction of a second.
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Oct 16, 2013 22:42
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grover posted:My favorite, though, are superconducting electromagnetic energy storage. Literally a coil of superconducting wire sitting in a tank of cryogenic helium that can dump out a SHITLOAD of power in a fraction of a second. This is a really interesting idea--haven't heard of it before. I work in a research MRI lab and was just thinking about how much energy might be stored. Do you have any interesting references off hand?
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Oct 16, 2013 23:18
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