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grover posted:The attitude I've seen is one of widespread and chronic complacency. They'll wear PPE if you call them them out on it, but get pretty bitchy about it. I wasn't specific enough. I meant what is management's approach?
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Mar 25, 2012 02:08
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ncumbered_by_idgits posted:I wasn't specific enough. I meant what is management's approach?
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Mar 25, 2012 02:19
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grover posted:The attitude I've seen is one of widespread and chronic complacency. They'll wear PPE if you call them them out on it, but get pretty bitchy about it. I agree. There are technicians and engineers I've run into who are over 50 and are pretty lax with a "well, we never did it that way and we never got shocked/killed/blown up." But even these guys are starting to see that they need to get with the times. Arc flash protection especially is becoming the name of the game. Customers are starting to ask for/demand products that can mitigate arc flash and provide additional protection to both their workers and power systems. I personally think stuff like 480 is the most dangerous. There's a sizable voltage there, but it's not quite high enough to turn heads. Still lots of electrocution and arc-flash potential, and the arc flash isn't always easy to nail down accurately. As far as NFPA 70E, I'm pretty by-the-book. I had to tell people "No, I can't/won't do this without higher level PPE" for monitoring a 120/208V panel that was directly downstream from a large transformer, where the arc flash was pretty high even for 120/208. They were cool with that. What scares me are places where people would pressure other people to do blatantly dangerous things. To be honest, my biggest fear in this industry is not being shocked, killed, or ending up in the hospital with the poo poo burned out of me in an oxygen tent. My biggest fear someday is lying in my bed at night thinking "I told John it was OK to work on that system live. His wife and little kids will never see him again." Three-Phase fucked around with this message at 02:39 on Mar 25, 2012 |
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Mar 25, 2012 02:26
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This might also be relevant to the current discussion: Jones is dead! Thank god we don't see many open-knife switches anymore. I've seen old rooms that had BIG knife switches that looked (and probably were) very dangerous. Three-Phase fucked around with this message at 02:38 on Mar 25, 2012 |
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Mar 25, 2012 02:35
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Was reading about the big switches used to cut power to large loads and the problem with arcing and what not. Back in physics class we had a transformer arranged as two pipes, inner windings and outer windings, the further you moved the inner winding inside the outer winding the higher the voltage goes. Why don't they use these as switches, you could keep the same voltage (or change it) and have a safe no contact way to isolate a circuit. I suppose it's because of inefficiency, I remember something about a ferrite core. Any ideas?
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Mar 25, 2012 03:05
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Three-Phase posted:To be honest, my biggest fear in this industry is not being shocked, killed, or ending up in the hospital with the poo poo burned out of me in an oxygen tent. My biggest fear someday is lying in my bed at night thinking "I told John it was OK to work on that system live. His wife and little kids will never see him again." One thing that gives me the heebie jeebies is when someone signs onto a lockout and attaches a lock to the box without bothering to verify the lockout for themselves.
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Mar 25, 2012 03:05
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It's burgin' time! 
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There's lots of pad transformers around campus, generally labelled with the building name that transformer serves and what I assume to be the amperage - ranging from 20A to 200A depending on the building. The union, for example, has a 100 amp service, if the bigass transformer is to be believed (it's about 4-5 ft tall). It's a massive 4 story building with a hydraulic elevator, has its own chiller, etc. Kinda curious what kind of voltage would be going in and out of those transformers, I'm assuming there's another transformer in the building to knock it down to 480. randomidiot fucked around with this message at 04:19 on Mar 25, 2012 |
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Mar 25, 2012 04:16
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mrmacomouto posted:Was reading about the big switches used to cut power to large loads and the problem with arcing and what not. Massive inefficiency. Something like this is kind of used, called an autotransformer, to manage line losses. Its an adjustable transformer, but adjusts by switching windings, not physically moving them relative to each other. Also you could potentially have some massive forces, trying to move windings with thousands of amps passing through them...
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Mar 25, 2012 04:44
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some texas redneck posted:The union, for example, has a 100 amp service, if the bigass transformer is to be believed (it's about 4-5 ft tall). It's a massive 4 story building with a hydraulic elevator, has its own chiller, etc. Kinda curious what kind of voltage would be going in and out of those transformers, I'm assuming there's another transformer in the building to knock it down to 480. There are a lot of different configurations possible. Typically the incoming voltage to service a building like that would be 13.8kV or 7200V. In the industry, that range (I believe from 600V to about 32kV is called "medium voltage"). The transformer might have multiple windings, so you have a configuration where you put 13.8kV in, and you get 277/480 out as well as 120/208 out on separate windings. In a system like that, you'll probably have really fat cables or busses coming out of the secondary going to a distribution center that then feeds power to panels throughout the building. In industrial facilities, you may feed a building with its own substation. On the extreme high end I've seen massive buildings fed with 138kV right from the power company's distribution system. In a large building or facility, you may use medium voltage both to feed power to different sections of a large building (2400, 4160, or 7200V) as well as running large motors (500HP to 10,000+ HP). In some systems you have what's called a "unit sub". On the far left side, you have a high-voltage load-breaking (typically load breaking?) disconnect switch that connects to the HV lines. That feeds an air-cooled transformer in the middle, and that feeds a distribution center to the right. The voltage you step down to can range from 120/208V to 5kV. mrmacomouto posted:Back in physics class we had a transformer arranged as two pipes, inner windings and outer windings, the further you moved the inner winding inside the outer winding the higher the voltage goes. I don't think that's an autotransformer. I think what you have is simply a transformer with a lot of losses by being able to reduce the area where the magnetic fields can effectively couple. Typically transformer are build with massive iron cores that can easily and efficiently accept the magnetic field. As a little factoid: autotransformers are "legal" for making small steps, typically called buck or boost transformers. (Not to be confused with buck or boost power supplies.) So if you have a two-pole, 208V breaker but need 240V, you can boost that. But it's forbidden to use an autotransformer to, say, go from 480V down to 120V. The reason is that if there's a break somewhere in the winding, the load can see the full voltage on the "primary". (This apparently doesn't apply to HV systems, I saw where three autotransformers the size of a small house were used to drop I think 800kVAC down to 500kVAC.) Three-Phase fucked around with this message at 12:41 on Mar 25, 2012 |
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Mar 25, 2012 12:31
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some texas redneck posted:There's lots of pad transformers around campus, generally labelled with the building name that transformer serves and what I assume to be the amperage - ranging from 20A to 200A depending on the building. Three-Phase posted:To be honest, my biggest fear in this industry is not being shocked, killed, or ending up in the hospital with the poo poo burned out of me in an oxygen tent. My biggest fear someday is lying in my bed at night thinking "I told John it was OK to work on that system live. His wife and little kids will never see him again."  Left a wife and two kids behind. Really brings home the dangers of complacency, though.
grover fucked around with this message at 15:30 on Mar 25, 2012 |
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Mar 25, 2012 15:14
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Since the subject is on arc flash, what's protocol for separating 480v power and 120v control in the same panel in order to lower PPE requirements? We have a customer who wants a control panel to do this. Essentially they want to be able to work on the 120v control side while it's live with minimal PPE, i.e. without having to wear the PPE that would be required if it were a 480v power panel. It was originally quoted as 2 separate enclosures bolted together with a pipe nipple to run wires between the two, but I've been told now that they only want a single enclosure "due to time constraints." I have a voice-mail out to the customer to clarify this as this makes no sense to me (it's just as fast for us to get 2 small enclosures or one large box). But for the time being, this is the directive, so my plan is to use a 2-door enclosure and having a custom bracket fabricated that will run the length of the subpanel and will reach as close to the center-post of a 60x60x12 enclosure as possible. So as far as actual arc flash, would this be considered an adequate barrier to lower the PPE requirement needed to work on the control side? There would be air gaps at the top and bottom of the enclosure, as well as an occasional hole punched through to run wires. It's essentially touch safe, but I don't know if that is adequate to lower the PPE. Follow up to that: Unless we ran wire through cord grips, there would be air gaps anyhow even if it were 2 separate boxes joined together via close nipple. Would that even be acceptable? Disclaimer: We are not arc flash experts and we do not guarantee any sort of 70E compliance whatsoever. We do not mark our panels with any sort of arc flash information aside from the generic warning label. We feel this is something that can only be done in the field, since we don't have all the information necessary to determine that.
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Mar 25, 2012 20:26
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DaveSauce posted:Since the subject is on arc flash, what's protocol for separating 480v power and 120v control in the same panel in order to lower PPE requirements? Two boxes nippled together should work pretty well, but what you're describing would probably only really suffice for reducing the shock hazard, not the arc-flash hazard. grover fucked around with this message at 20:53 on Mar 25, 2012 |
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Mar 25, 2012 20:51
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If you wanted to (potentially) dramatically lower PPE as well as increase protection dramatically, install a fused disconnect switch with current limiting fuses before you feed into the panel (like a drive, etc.) This would be ideal for cabinets you expect will need to be checked/modified/maintained periodically. For a modern drive, on a dual-element fuse you should never have an overload trip since the drive would stop working (overload alarm/fault) before the fuse blew (if properly coordinated). If the instantaneous, current-limiting section blows, then you've got something really wrong downstream of the fuse. You get the added benefit that you can dramatically limit damage within a cabinet. I had a line-to-line 480V short in a drive cabinet. I heard a quiet "pop" sound, smelt burning plastic death, and noticed the drive died. Without the fast-acting fuses we selected, we might've blown the cabinet apart inside and had a major incident. Be advised that adding fuses or other changes to the power system is not a silver bullet, you still need to have an experienced electrical engineer look at the system and analyze the potential exposure levels. I'm not yet experienced enough to do that, and I don't pretend that I am comfortable doing arc flash equations. (Not yet at least.) Grover - are there any things like Lexan shields that could be installed in a cabinet to mitigate arc flash? (I doubt it, I've never seen anything like that, except for "touch-proof" shielding.) Three-Phase fucked around with this message at 23:14 on Mar 25, 2012 |
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Mar 25, 2012 23:11
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Three-Phase posted:Grover - are there any things like Lexan shields that could be installed in a cabinet to mitigate arc flash? (I doubt it, I've never seen anything like that, except for "touch-proof" shielding.) Arc-flash explosions look like simple explosions in video online, but in actuality, it's comprised of plasma which is heavily impacted by electromagnetic fields, and doesn't necessarily work like you think. I've heard stories of metal doors blown clean off a switchboard and thrown into the opposite wall, yet an insulator just inches away come through without so much as discoloration.
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Mar 25, 2012 23:21
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Three-Phase posted:Be advised that adding fuses or other changes to the power system is not a silver bullet, you still need to have an experienced electrical engineer look at the system and analyze the potential exposure levels. I'm not yet experienced enough to do that, and I don't pretend that I am comfortable doing arc flash equations. (Not yet at least.) Please give me work... I also haven't done an actual arc flash calculation since studying for my PE exam. I just plug that poo poo into SKM and it poops out the incident energy levels for me. Its actually pretty simple. The only problem is that if you have a partial electrical system, using an infinite bus on the transformer is not necessarily a good idea. You need to model more of the system. On another topic, does anyone know how to put ground fault protection on a DC supply feed from a PV system? CTs obviously won't work so how do you actually build a residual current device to trip a ground fault? Eaton tells me that they do not build a dc GFP device and I am a bit perplexed as NEC requires it. Cheesemaster200 fucked around with this message at 04:38 on Mar 26, 2012 |
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Mar 26, 2012 04:24
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grover posted:Transformers like that are typically labled in "kVA". 100kVA ~ 277A at 208/120V 3-phase. The transformer you're describing sounds more the size of a 500-750kVA transformer, though. Can you read the nameplate on it? I'll be in that area tomorrow, I'll try and snap a photo. I do know that not too far away, there's another transformer for the same building, but a bit smaller and with external cooling fins (oil filled I assume). I'm assuming that final one is what drops it down to either 277 or 480. The tag that says "100A" is something printed by the installer or electric company or something, but the university does have at least one substation of their own (along with its own zip code). I don't see a building this size being able to run on only 277A - not with the chillers, elevator, etc. But the nameplate will say all. randomidiot fucked around with this message at 05:28 on Mar 26, 2012 |
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Mar 26, 2012 05:25
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Three-Phase posted:This might also be relevant to the current discussion: I was just browsing this thread because I'm going to ask some electricity questions when I get my bandsaw revamped, but I just bought an old 40's or 50's bandsaw that features that exact SquareD switch and my friend was joking that it will somehow kill me. Forgive the utter ignorance but is this switch a bad thing or a better thing than a previous bad thing?
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Mar 26, 2012 16:21
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Not an Anthem posted:I was just browsing this thread because I'm going to ask some electricity questions when I get my bandsaw revamped, but I just bought an old 40's or 50's bandsaw that features that exact SquareD switch and my friend was joking that it will somehow kill me. Forgive the utter ignorance but is this switch a bad thing or a better thing than a previous bad thing? 
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Mar 26, 2012 16:39
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^ GEEZ. Now that's scary. Are those two lower ones near the middle hand-operated rheostats or switches with arc chutes?  Cheesemaster200 posted:The only problem is that if you have a partial electrical system, using an infinite bus on the transformer is not necessarily a good idea. You need to model more of the system. I've read that for looking at short circuit fault calculations, using an infinite bus will give you the worst-case fault currents. However, there are situations where using an infinite bus may actually (inaccurately) lower the arc flash levels because the extremely high fault levels may cause equipment to trip faster than at lower currents. Not an Anthem posted:I was just browsing this thread because I'm going to ask some electricity questions when I get my bandsaw revamped, but I just bought an old 40's or 50's bandsaw that features that exact SquareD switch and my friend was joking that it will somehow kill me. Forgive the utter ignorance but is this switch a bad thing or a better thing than a previous bad thing? You'd be surprised how well old equipment can work. It seems like stuff back then was really overbuilt too. I wish I could find a big version of the Andry-Farcy advertisement poster for Merlin-Gerin. Anybody here work at Schneider Electric? Three-Phase fucked around with this message at 01:29 on Mar 27, 2012 |
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Mar 27, 2012 01:17
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Three-Phase posted:You'd be surprised how well old equipment can work. It seems like stuff back then was really overbuilt too. Old woodworking stuff is tits, there are sites dedicated to old stuff (oldwoodworkingmachinery, vintagemachinery, etc), I just don't know electricity. Trying to learn 
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Mar 27, 2012 04:36
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grover posted:That SquareD switch is fine, so long as it's in good condition. It was an exposed knife switch that killed poor Jones. I can't imagine surviving very long in a place like that. Familiarity breeds complacency and all that. I'd go for one of the upper switches and... *zap* Brushed my hand on one of the lower ones.
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Mar 27, 2012 06:13
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Crackpipe posted:I can't imagine surviving very long in a place like that. Familiarity breeds complacency and all that. I'd go for one of the upper switches and... *zap* Brushed my hand on one of the lower ones. I think this is one of those things to be touched only with a ten-foot pole.
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Mar 27, 2012 20:14
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Three-Phase posted:I've read that for looking at short circuit fault calculations, using an infinite bus will give you the worst-case fault currents. However, there are situations where using an infinite bus may actually (inaccurately) lower the arc flash levels because the extremely high fault levels may cause equipment to trip faster than at lower currents.
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Mar 27, 2012 22:31
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Now as far as arc flash mitigation goes, I've seen three technologies out there that might help: 1. Breakers with an arc-flash reduction setting: when someone's working downstream and live, you set the breaker to basically have a "hair trigger" trip setting 2. Fiber-optic sensors that detect the brilliant light from an arc and tells the upstream breaker to trip immediately 3. GE Arc-Vault system, where an arc is detected by light and a sudden dI/dt and basically "shunted" into a special canister upstream that generates/contains the fault until the breaker opens Siemens is also selling medium-voltage GIS for 4160V to I think 38kV, and since everything is contained in gas-insulated ducts, there's no live equipment to interact with or test, so there's inherently no real risk of arc flash within the switchgear itself. As far as fault levels, where I've worked it's not uncommon to have a >100MVA fault potential. (100MVA probably is enough to run a large town.) Three-Phase fucked around with this message at 10:46 on Mar 28, 2012 |
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Mar 28, 2012 10:44
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I live in an older neighborhood with lots of trees and all of our power is overhead wires. Last spring we had some bad storms and were without power for 6 days one week and 4 days 2 weeks later. This spring the utility is doing some work that I'm guessing has to do with getting the system ready for spring storms. the main streets have 3 phase medium voltage service on the poles and between each side street is a single phase branch that runs down the back yards to feed transformers for the houses on those streets. Where the branch line ties into the main line theres a fuse/switch device. Over the last few weeks they've been replacing these fuses with new ones that have a big canister hanging off the bottom. It appears to be about the size of a 1 liter bottle. They seem to attach to the existing fuse holders. Any idea what this is.
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Mar 29, 2012 03:48
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Can you take pictures with a convenient angle/zoom to them?
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Mar 29, 2012 04:08
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If you've ever wondered how long it takes to boil the inside of a tree at 33kV, wonder no more! https://www.youtube.com/watch?v=8IGOsDBlP0s
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Mar 29, 2012 08:33
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Drheat posted:It appears to be about the size of a 1 liter bottle. They seem to attach to the existing fuse holders. Sounds like a single-phase recloser. Basically, when you have a fuse, in a short circuit or overload condition, it'll blow to protect equipment in the power system from damage. With a recloser, you have a circuit breaker (probably a vacuum interrupter or SF6 breaker) that detects a fault, opens the circuit, waits, and then tries to close. Here's a little scenario where a recloser is useful. You have a power line that services a section of a town. The line is 13kV, and the circuit breaker feeding that section has a recloser. Let's assume for simplicity that the system is referenced to ground. You have a squirrel, let's call him "Fluffy". Little Fluffy climbs the power pole, and while standing on the crossarms, tries to climb up on an insulator and grabs the line, completing a path from phase A to ground. (I will spare the gory details about Fluffy's fur catching on fire and various other unpleasantness that 13kV going into a small mammal causes.) Eventually there is a good enough current path that the line arcs over to ground with a brilliant flash of light and a loud bang. The relaying at the substation sees a fault on one of the lines, and waits until it reaches the correct point in the time-current curve to trip the circuit breaker. Once the line flashes over, it immediately decides the breaker must open NOW. The fault is interrupted within a cycle or so, the lightshow ends, and Fluffy's cremated body falls from the line. The recloser waits three seconds, then commands the breaker to close. The breaker closes, and since there's no fault, everything ends fairly well. (Except for Fluffy.) The Proc posted:If you've ever wondered how long it takes to boil the inside of a tree at 33kV, wonder no more! It looks like you can see recloser action in this very video! 4:02 - Severe fault (brilliant flash) 4:03 - Fault interrupted (probably between 10-30 cycles) 4:13 - System attempts to reclose (ten seconds after initial interruption) 4:18 - Another flash, system interrupts again, goes into lockout (recloser does not attempt to close breaker again) Three-Phase fucked around with this message at 00:44 on Mar 30, 2012 |
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Mar 30, 2012 00:36
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Three-Phase posted:3. GE Arc-Vault system, where an arc is detected by light and a sudden dI/dt and basically "shunted" into a special canister upstream that generates/contains the fault until the breaker opens As far as I know these are bottom entry only for cables, I'm in the mining industry so we can't use these underground, have to go with something that has top or side entry only. On a side note, I am writing up a small proposal for a problem a mining company is having. They operate their main hoist using a VFD and whenever they put the brakes on the hoist, the 1750HP fan on the same bus vibrates like crazy and generates a lot of noise in its power factor correction capacitors. It's a bit beyond me as I'm relatively new, but I'm set up to work with a harmonics expert on this project and i'm really looking forward to see how harmonics work and can be corrected in industry.
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Mar 30, 2012 00:52
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Meow Meow Meow posted:On a side note, I am writing up a small proposal for a problem a mining company is having. They operate their main hoist using a VFD and whenever they put the brakes on the hoist, the 1750HP fan on the same bus vibrates like crazy and generates a lot of noise in its power factor correction capacitors. It's a bit beyond me as I'm relatively new, but I'm set up to work with a harmonics expert on this project and i'm really looking forward to see how harmonics work and can be corrected in industry. That does sound pretty interesting. Are you talking 1000, 2400, or 4160VAC here? Just out of curiosity, how far is the distance between the VFD and the motor for the hoist?
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Mar 30, 2012 01:26
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Meow Meow Meow posted:As far as I know these are bottom entry only for cables, I'm in the mining industry so we can't use these underground, have to go with something that has top or side entry only. Be sure to post a followup on this one. 
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Mar 30, 2012 02:02
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some texas redneck posted:I'll be in that area tomorrow, I'll try and snap a photo. Photo, though not good enough to make out the full name plate. Thought it said 100A, it actually says 100 AMP. This one is about 4 1/2 ft tall. There's a ton of these around campus, each labelled with a building name, what I assume to be a circuit #, and amperage. Some are labeled with up to 3 buildings, a few are labeled "SPARE". The mfg date is 2008 on this particular one; 2006-2011 for most of the ones I've seen around campus. If I had to guess I'd say they moved a lot of lines underground, I can't see any other reason for a shitload of new pad transformers all over campus; parts of the campus dates back to the late 1890s, with the majority of it dating to the 1940s. The building this one serves was built in several phases from the mid 60s to the early 70s. 
randomidiot fucked around with this message at 03:31 on Mar 31, 2012 |
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Mar 31, 2012 03:24
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some texas redneck posted:Photo, though not good enough to make out the full name plate. Thought it said 100A, it actually says 100 AMP. This one is about 4 1/2 ft tall. There's a ton of these around campus, each labelled with a building name, what I assume to be a circuit #, and amperage. Some are labeled with up to 3 buildings, a few are labeled "SPARE". The mfg date is 2008 on this particular one; 2006-2011 for most of the ones I've seen around campus. If I had to guess I'd say they moved a lot of lines underground, I can't see any other reason for a shitload of new pad transformers all over campus; parts of the campus dates back to the late 1890s, with the majority of it dating to the 1940s. The building this one serves was built in several phases from the mid 60s to the early 70s. 100 Amp probably refers to the rated current of the switchgear. I typically haven't seen devices that are labeled that way as that information is usually stamped on the nameplate, but there's nothing wrong with labeling it that way.  It looks like a S&C Live Front pad mounted switchgear. Not a whole transformer, that has to be elsewhere. Maybe a unit-sub in a building, maybe in a vault underground. Does your campus have an EE/EET department? You might find a someone there who would be happy to explain the distribution system. (Be aware that post-9/11, people are probably going to be leery if you ask for or post online things like one/three-line diagrams, details on protection systems, SCADA systems, or photograph parts of whole substations.) Three-Phase fucked around with this message at 11:44 on Mar 31, 2012 |
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Mar 31, 2012 11:33
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Three-Phase posted:Sounds like a single-phase recloser. Thats exactly what it is. In fact its exactly that model. Interesting idea, but I don't think its going to help much in our area. We don't have issues with nusance outages due to animals or rubbing tree branches. All of our outages are due to the wires being on the ground and I don't see a recloser helping with that situation.
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Apr 1, 2012 04:46
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Drheat posted:Thats exactly what it is. In fact its exactly that model. It sounds like the problems might go hand-in-hand. The tree branches can contact the lines, especially if there's a bad storm that knocks down trees, and the trees may also give small mammals access to the lines. Reclosers are not a suitable replacement for proper tree trimming.
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Apr 1, 2012 12:13
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Speaking of things seen about the neighbourhood, I was on my way to work today and saw some linespeople at work. On some of the lines, there were what looked like bright orange sleeves. I assume they weren't just feeling festive?
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Apr 6, 2012 02:01
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Those orange mats are there as insulation. It stops linesman from being the jumper between circuits.
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Apr 6, 2012 07:18
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Three-Phase posted:Reclosers are not a suitable replacement for proper tree trimming. I think the local power company here in Oregon has gotten fed up with downed lines due to trees. They just did a machivellian 10+ foot trim around just about every line... not pretty, but they're not paid to be landscape architects.
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Apr 6, 2012 21:13
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Bio-Hazard posted:I think the local power company here in Oregon has gotten fed up with downed lines due to trees. They just did a machivellian 10+ foot trim around just about every line... not pretty, but they're not paid to be landscape architects. I don't blame them. I'm wondering if a homeowner is on the hook if they have a dying "killer tree" on their property that falls over onto nearby power lines?  We haven't talked much about ladder logic. This is an example control panel for a ventilation blower for a mine shaft. I'll have to draw up a sample ladder logic diagram to show how one of these would be connected up. Also, I finally found another (thankfully minor) arc-flash accident video. The guy is clearly alive, but he still may have suffered burns and vision damage from his face being in front of the arc like that. Towards the end you can see zoomed in and slow-mo the man engulfed in the flash. It looks like, using his right arm, he reaches in and manipulates something, then reaches back in, and as his arm reaches the end of motion, the arc flash occurs. What is funny/creepy: after the arc flash, there does appear to be a worker nonchalantly walking behind the panel that just had an arc flash and is spewing smoke like nothing unusual has happened.  And for one last treat - that sweet sound of transformers starting. Three-Phase fucked around with this message at 23:57 on Apr 6, 2012 |
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Apr 6, 2012 23:38
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Three-Phase posted:And for one last treat - that sweet sound of transformers starting.
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Apr 7, 2012 00:32
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