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Pressurized water, none of that radioactive craziness. Repeat after me, Contamination is a myth. Although we do train for steam generator Utube ruptures. We shifted the pumps to an alternate source at their slower speed after the loss. And no MV, riddle me this. Antiquated but reliable 450V Switchgear. Its the most obnoxious part of my job. Why are their 20 cables going into that switchboard you ask? For one breaker you say! Breaker contact pitting due to kA transients are a pain to replace.
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Jul 14, 2013 00:39
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Oh wow. My mind is blown that you wouldn't be using MV pump motors.
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Jul 14, 2013 00:45
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Frozen Horse posted:The highest voltage circuit I've been around lately was a bit more than that, but only about 100 mA. On the other hand, it was a 100 mA beam current at 7 GeV or so. At that point, it's a beam of electrons in ultra-high vacuum. What capacitors do you use for the linear accelerator?
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Jul 14, 2013 02:17
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Frozen Horse posted:The highest voltage circuit I've been around lately was a bit more than that, but only about 100 mA. On the other hand, it was a 100 mA beam current at 7 GeV or so. At that point, it's a beam of electrons in ultra-high vacuum. I noticed that there are warnings about hi-pot testing vacuum contact bottles. If you apply a high voltage to them, they will emit x-rays.
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Jul 14, 2013 03:58
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Frozen Horse posted:The highest voltage circuit I've been around lately was a bit more than that, but only about 100 mA. On the other hand, it was a 100 mA beam current at 7 GeV or so. At that point, it's a beam of electrons in ultra-high vacuum. It's not voltage that's causing the beam of electrons to give off radiation. Any changed particle will radiate when accelerated (as when going around a bend). You could send the beam through a plain old permanent magnet to bend it and still get x-rays off. Or crash them into a piece of metal and get bremsstrahlung x-rays, which is how x-ray machines usually work. What is high-voltage are the klystrons that generate the RF that is used to accelerate the electrons. The klystrons used in accelerators have peak voltages of something like 500 kV. They each put out megawatts of microwave power each. Microwave frequencies don't travel well through normal wires, so instead they're piped through waveguides from the klystrons to the beam tunnel. Specially-shaped cavities there accelerate the electrons. The cavities and the RF are tuned so that the accelerating voltage across each cavity is at the peak just when the electrons are passing through. The electric field accelerating the electrons ends up being measured in the MV/m.  That red thing is the klystron. The beam line is actually something like 10 m underground. You can see the waveguide coming out of the top. It's the weird copper pipe with a rectangular cross-section coming out of the top. Enilev fucked around with this message at 05:12 on Jul 14, 2013 |
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Jul 14, 2013 05:07
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Here's one of the Argonne scientists loving around with the high-powered magnets in a Klystron during a test many years ago.
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Jul 14, 2013 14:23
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Enilev posted:It's not voltage that's causing the beam of electrons to give off radiation. Any changed particle will radiate when accelerated (as when going around a bend). You could send the beam through a plain old permanent magnet to bend it and still get x-rays off. Or crash them into a piece of metal and get bremsstrahlung x-rays, which is how x-ray machines usually work. The frequency is dependent on the energy of the beam for a given bending magnet, thus why we need a high-energy beam. The fun part of it is that you can send the beam repeatedly through klystron-driven cavities, accelerating it more each time. Thus, we get electrons with an energy equivalent to current flowing across a multi-GV potential. However, I now do have more sympathy for the HV power supply folks who had something go pear-shaped during my most recent beam time, which caused a beam dump and a few hours extra for lunch. Three-Phase posted:I noticed that there are warnings about hi-pot testing vacuum contact bottles. If you apply a high voltage to them, they will emit x-rays. That would be due to the bremsstrahlung mentioned above. If you get electron emission from the negative terminal, the electrons will be accelerated to the positive side where they slam into it and are vigorously decelerated and in the process emit x-rays. You can get similar emission from things like vacuum arc-furnaces and even some types of vacuum-tube electronics.
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Jul 14, 2013 19:58
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Frozen Horse posted:The frequency is dependent on the energy of the beam for a given bending magnet, thus why we need a high-energy beam. The fun part of it is that you can send the beam repeatedly through klystron-driven cavities, accelerating it more each time. Thus, we get electrons with an energy equivalent to current flowing across a multi-GV potential. However, I now do have more sympathy for the HV power supply folks who had something go pear-shaped during my most recent beam time, which caused a beam dump and a few hours extra for lunch. Yeah, this is why old CRTs (remember those?) have a very thick leaded glass front face. Well, the very thick part is because they have to handle a hard vacuum and are a giant goddamn sheet of almost flat glass. It's very hard to make glass not break under those conditions, so the screen is arched slightly so that it can handle the vacuum force entirely in compression rather than having to handle tension on the inner face of the screen. Anyways. The front is leaded glass to block X-rays that may be formed if the horizontal output transformer voltage is too high. On older TVs built using vacuum tubes, the horizontal output transformer's rectifier tube (example part number: 1Y2) that is used to provide anode voltage to the CRT is generally enclosed in a metal box along with (on some models) the beam power triode (6BK4A springs to mind) usually used as a shunt voltage regulator - also to block X-rays. I've even seen some manufacturers tubes of these types with X ray warnings printed on the glass.
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Jul 14, 2013 22:49
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I saw this video and thought of this thread. Nice aftermath in this video - you don't usually get to see wires on fire. There's a video I've been trying post here but haven't been able to find - it's a detailed advertisement/tutorial video for splicing gigantic three-phase cables, where each cable is about the width of the worker's arm. Similar style to this video that was just posted, though (slightly) higher production quality. Amazing how much care goes into it, and it's a beautiful procedure. Anyone know where I might find that? I seem to recall there was another rather terrifying video involving doing it on a live cable without service interruption, but I could be misremembering that one. (also why do searches for "three phase splice" keep giving me soft-porn workout videos, seriously google, what the hell)
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Jul 15, 2013 13:13
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ZorbaTHut posted:(also why do searches for "three phase splice" keep giving me soft-porn workout videos, seriously google, what the hell) Apparently "Phase Splice 3" is some model or brand of gym tights.
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Jul 16, 2013 02:01
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Alien Arcana posted:Apparently "Phase Splice 3" is some model or brand of gym tights. Huh. That's surprisingly reasonable. Alright Google, I'm sorry I doubted you.
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Jul 16, 2013 11:33
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I was looking for switchgear videos and did come across this one ( due to some coarse language). The install work looks pretty nice and they seem to have a fairly cohesive crew (nobody telling anyone to go f themselves). If this video gives you pause, be aware this isn't that unusual, especially at a factory. (However things are much less lax in many places now due to both legal concerns and workplace violence concerns.)I've worked with surprisingly gentleman-like electricians and the more rough-and-ready variety, both union and nonunion. If they get the job done, do it right, and do it safely, (and aren't too rowdy) they're allright in my book. Three-Phase fucked around with this message at 02:07 on Jul 18, 2013 |
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Jul 18, 2013 02:03
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Three-Phase posted:I was looking for switchgear videos and did come across this one ( This is exactly my job. The lovely camaraderie, the descriptive language, and the excellent pipework and wonderful wire terminations. Also, coming in on Saturday, with half the crew, and one dude walkin around doin nothin, but he buys the pizza, so it's OK.
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Jul 18, 2013 22:22
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Speaking of splices - I've seen kits that are "cold shrink", where the material is under tension, and you can unwind a piece of material that causes it to compress down. I could see where this would be useful at facilities that are really picky about hot work permits or where time was of the essence to get something back online, but I've also heard that this is a little more hokey and inferior to splices and terminations that use heat-shrink covers. (Hot work permits are for using things like propane torches. It's a safety thing that helps to prevents fires and injuries.) Three-Phase fucked around with this message at 22:44 on Jul 18, 2013 |
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Jul 18, 2013 22:34
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Three-Phase posted:Speaking of splices - I've seen kits that are "cold shrink", where the material is under tension, and you can unwind a piece of material that causes it to compress down. I could see where this would be useful at facilities that are really picky about hot work permits, but I've also heard that this is a little more hokey and inferior to splices and terminations that use heat-shrink covers. Cold shrink is a direct replacement for heat shrink, and is just as good. The 3M guy that came by our jobsite sold both kits, and said it was up to us which to use. We used cold shrink in the summer and heat shrink in the winter. Never had a splice, tap, or termination fail that I know of. Both kits are basically the same except for the last step.
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Jul 18, 2013 22:40
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babyeatingpsychopath posted:Cold shrink is a direct replacement for heat shrink, and is just as good. The 3M guy that came by our jobsite sold both kits, and said it was up to us which to use. We used cold shrink in the summer and heat shrink in the winter. Never had a splice, tap, or termination fail that I know of. Both kits are basically the same except for the last step. That's good to know - it is much faster and you don't need to mess with the hot work permits.
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Jul 18, 2013 22:45
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Just did a 16 hour shift holding our breath while we almost broke our all time peak MW usage. Our record was 13,189 MW's set in july 2011 - today we hit 13,161 MW. We lost surprising few distribution feeders. The night is still young though and we still have 3 more days of high 90 degree weather with humidity. I am glad I am now off until Sunday night. woo! here is a picture just for picture's sake:  ABB 138KV breaker. Some Guy From NY fucked around with this message at 03:37 on Jul 19, 2013 |
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Jul 19, 2013 03:13
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Over the next three days my crew and I have to test 35 runs of 25kV cable (i.e. 105 individual cables) and 11 25kV S&C fused air switches. One of the electricians for our client almost got his poo poo wrecked today. We were up at 78 kVDC on a cable from the MV switchgear to the MV switch, testing from the switchgear and dead-ending at the switch. Dude ducked underneath our danger tape and warning signs at the switch and opened up the door so he could take some pictures for idk what. 
Noctone fucked around with this message at 03:48 on Jul 19, 2013 |
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Jul 19, 2013 03:46
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Noctone posted:Over the next three days my crew and I have to test 35 runs of 25kV cable (i.e. 105 individual cables) and 11 25kV S&C fused air switches. Ha, I have people do that all the time to me. I will be infront of a high voltage test set performing a high-pot, with the cable going to the G&T device with everything roped off with danger tape and signs...and guys will still go around/under the tape, step OVER the cable which is putting out 25KV to come ask me if "I'm busy". and these are career substation workers.    Some Guy From NY fucked around with this message at 04:10 on Jul 19, 2013 |
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Jul 19, 2013 04:02
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Hahahahaha figures. Ironically, electricians seem to keep their distance the most on low voltage circuit breaker testing, which is far and away the least dangerous thing we do (high current but very low voltage [7VAC or so], so the only danger is burning yourself on the cables/bus connecting the test set to the breakers).
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Jul 19, 2013 04:22
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Some Guy From NY posted:
It's like the big brother of ABB's 35kV variant.  I like the bigger model, I think it's a vacuum-bottle in SF6 design they have for 500kV, and I think you gang two in series for 800kV. People have no idea how dangerous this stuff is. At least you had a proper warning. I once caught someone doing hi-pot testing with insulating blankets on the equipment but without a door lock or warning sign of any sort on the equipment and I hated to do it but I chewed them out for it. They quickly corrected the problem. If you want to have some fun, show non-electrical people the Westex arc flash test videos. How wide their eyes become when they see the mannequin on fire. Three-Phase fucked around with this message at 11:36 on Jul 19, 2013 |
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Jul 19, 2013 11:28
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Wheehaw. Modern safety gear is amazing stuff. Yeah, it's a nasty explosion at close range, but with the proper gear no lasting damage happens.
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Jul 19, 2013 12:46
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Some Guy From NY posted:Ha, I have people do that all the time to me. Part of the problem is that we don't have clear distinctions between "hey, we're busy here, public keep out" and "DO NOT loving CROSS THIS LINE OR YOU WILL DIE" kinds of tape.
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Jul 19, 2013 14:30
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grover posted:I bolded the important bit. I think the problem is that caution tape applies to other people, laymen, not trained professionals who often set up their own caution tape. I widely ignore the tape, too. I became self employed after working for an equipment manufacturer doing a lot of testing and troubleshooting on switchgear and I had the hardest time to adjust to hands-off data collection. Sometimes you need to get relay settings and it's just so tempting to just start fiddling with the menus and get them at the spot. Nothing can happen, but when the whole production goes down and you've been seen touching the relays there'll be a world of poo poo. Nowadays I just keep my hands on my back and stay within the blue lines visiting the factory and follow the lead of whoever is escorting me.
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Jul 19, 2013 15:05
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Some Guy From NY posted:Just did a 16 hour shift holding our breath while we almost broke our all time peak MW usage. Our record was 13,189 MW's set in july 2011 - today we hit 13,161 MW. We lost surprising few distribution feeders. We've got a lot of those in the Cleveland area. We've had 3 or 4 blow up in the past few years, and ABB is assisting with the teardown and return of the latest one so they can assess the potential for design faults being the root cause. They have cost us a couple of 138 transformers so far.
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Jul 19, 2013 15:41
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grover posted:I bolded the important bit. I think the problem is that caution tape applies to other people, laymen, not trained professionals who often set up their own caution tape. I widely ignore the tape, too. Use red danger tape for the latter? http://safetywiki.pppl.wikispaces.net/Barricade+Tape
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Jul 19, 2013 17:58
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We use caution tape with signs describing the hazard in places were you want people to avoid. For places that people must not pass through we use danger tape and it is taken quite seriously if someone was to go through.
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Jul 19, 2013 19:52
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grover posted:Part of the problem is that we don't have clear distinctions between "hey, we're busy here, public keep out" and "DO NOT loving CROSS THIS LINE OR YOU WILL DIE" kinds of tape. Yellow/black or yellow tape (caution) versus red/white, red/white flagged, or red tape (danger).
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Jul 19, 2013 21:07
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FistEnergy posted:We've got a lot of those in the Cleveland area. We've had 3 or 4 blow up in the past few years, and ABB is assisting with the teardown and return of the latest one so they can assess the potential for design faults being the root cause. They have cost us a couple of 138 transformers so far. I think I've seen seen some in the big substation near East 49th street that appears to feed facilities in the Industrial valley. 345 to 138, right? (BTW, be sure to not post anything that is proprietary/sensitive that could get you in trouble!)
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Jul 19, 2013 21:16
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Three-Phase posted:Yellow/black or yellow tape (caution) versus red/white, red/white flagged, or red tape (danger).
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Jul 19, 2013 21:19
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Hmmm that is interesting to hear about the ABB breakers failing. We have dozens and dozens on the system, including my home substation. We have not had any issues with these breakers anywhere in our company as far as I know, except for one defective one where the pressure relief valve was installed literally backwards from the factory and it blew up. Other than that we are continuing to replace older breakers with them. Mad scientist breakers activate! (modified 345KV SFA breakers)   Here is the original:  This was an air insulated, air open/ air close 345KV breaker from what I was told. This one in the picture was the last one in service in our system before being replaced (as seen in the pic) 5 years ago. It has THREE interrupters per phase, opposed to the "newer" modified version with just 1 interrupter in the football shaped head. The 2 huge columns on either side contain CT's in the round tanks at the bottom. Some Guy From NY fucked around with this message at 23:10 on Jul 19, 2013 |
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Jul 19, 2013 23:07
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We have one generation station in our system with similar breakers. 3 interrupters per phase. They are very large and weird, and only some of the old-timers have experience rebuilding them. I call them the Rube Goldberg breakers.
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Jul 19, 2013 23:26
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Three-Phase posted:Bad installation that failed at a fairly low hi-pot (high potential) test.  How does anyone who's ever seen so much as a cable TV wire not look at that and immediately recognize that something is horribly wrong?
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Jul 20, 2013 21:34
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Since we're talking splicing and connections, I don't think I've seen a video with a bigger conductor at a higher voltage than this: ABB Kabeldon CD 145kV termination "Plug-in" for GIS switchgear.   I really want a pair of ABB pants. Wanted to share this as well. It's clearly from an old VHS tape, but the contents are still valid, and it's explained in a pretty good way. Three-Phase fucked around with this message at 02:38 on Jul 27, 2013 |
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Jul 27, 2013 02:22
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I just read a Three-Phase post in another thread where he was talking about generators backfeeding the power grid, wouldn't that mean they're providing power to their neighbours houses too?
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Jul 31, 2013 02:19
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Crankit posted:I just read a Three-Phase post in another thread where he was talking about generators backfeeding the power grid, wouldn't that mean they're providing power to their neighbours houses too? In theory, yes. If the line feeding a row of houses go out, and you have a generator connected to the panel at your house, and the main breaker is closed or a fuse is in place, the 240V will flow "backwards" out of panel, through the pole transformer (240V to 7200V or 13.8kV), then with the section of power line energized, it will flow through your neighbor's transformer (7200V or 13.8kV to 240V) and into their home. Asides from opening the circuit, there's no practical way to prevent the power from flowing in the opposite direction. I use "in theory" because depending on where the fault is that isolates your power lines from the grid, unless the generator is huge (for a home that is) the generator will not only need to supply power to the loads in your house, but all the other loads on the line (the other houses), severely overload, and it will trip its breaker. However there have been situations where linemen have been killed by backfeeds. The generator is far more current-limited than the power grid, but it still can put enough current into a power line at high voltage to injure or kill. If you are going to do this, you need someone to come and install a bypass switch. It either connects your home to the power grid, or your generator, but never both at once. You can also put in a separate sub-panel that (through a bypass switch) can be fed by your main panel or a generator, so you can have critical circuits (furnace/heater, water pump, refrigerator, computer and modem, TV) that can be powered from the generator and the rest of the house goes dark. Sometimes these bypass switches are just two circuit breakers with a mechanical interlocking that physically prevents both from being closed at one time. You have have both open, one of the two open, but never two closed at the same time. I've worked with some Eaton UPS units that have a sliding metal panel that prevents this from happening, a mechanical interlock. Three-Phase fucked around with this message at 00:15 on Aug 1, 2013 |
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Aug 1, 2013 00:08
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What about solar and/or wind generation that allows for sending power back into the grid?
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Aug 1, 2013 00:22
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Guy Axlerod posted:What about solar and/or wind generation that allows for sending power back into the grid? It would need circuitry to detect the loss of the grid ("islanding" or loss-of-connectivity) and fault out. It's not simple to do because you can be operating in different conditions with the inverter synchronized to the power grid: - Heavy load in the house, using power from both the alternative and grid source - Light load in the house, sending power from alternative to grid - Equal loading of the home and alternative source, no power from the grid There's an article here that talks about detecting islanding conditions. Three-Phase fucked around with this message at 00:35 on Aug 1, 2013 |
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Aug 1, 2013 00:31
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Three-Phase posted:It would need circuitry to detect the loss of the grid ("islanding" or loss-of-connectivity) and fault out. It's not simple to do because you can be operating in different conditions with the inverter synchronized to the power grid:
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Aug 1, 2013 00:36
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How are brownouts managed, in the context of load-shedding? Ontario had one a number of years ago, and this was the reason given.
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Aug 9, 2013 04:08
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