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Two Finger posted:this is no loving joke man. Happens all the time in the Brisbane River. Have to swing sea suctions, clean strainers whilst steaming! A couple of fire hoses on strong jet pointed to near the suction is the trick. Not sure if it rips the jellies apart or just pushes them away a bit. Definitely works.
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Oct 23, 2015 12:27
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TheFargate posted:That really depends on the electric company. For us, if one phase goes down, the other 2 do as well. Then if its a 13kV circuit, the system will automatically try to restore power to as many customers as possible. If its a 4kV circuit, you wont get power back until the lines are repaired. Other than something taking out 2 phases (i.e. a falling branch or some such) no clue how you could lose 2 phases. Yeah "it depends". On our system we have many hydraulic non-SCADA individual reclosers on 3 phase lines. AKA "triple singles". So you can lose individual phases, won't drop the whole line. As a matter of fact, I saw it firsthand at my house a couple of weeks ago during our biblical flooding here in SC. My power comes from a single phase tap, that feeds off a 3 phase line. A tree got washed out in a branch (you may call it a stream or creek), and fell over on the 3 phase, only taking out one of the phases initially - the same one that feeds my tap. On the 3 phase just past my tap, there is a wye-delta transformer bank with floated H2s, which will backfeed if you lose a phase. Until I could run into my utility room and hit the main breaker, my lights were going dim and bright, relays in the stove and fridge clicking like crazy, just like you describe.
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Oct 23, 2015 18:00
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In other news, this happened to me Tuesday: Switching operation, taking a substation out of service for repairs. Was closing this normally open set of switches to backfeed this circuit from another station. Switch failed as you see, but luckily somehow it hung from my stick and didn't fall on that tap, which would have been a phase to phase fault right above my head. Was able to ease it down and hang in the clear. Engineer wanted to just change out the failed switch, and try to close in the other two, change them out later, get this backfeed done so the station work could commence. I looked closely and found cracks in one of them, so they begrudgingly let me change out all three. ... The cracked switch I saw, broke while I was removing the conductor. angryrobots fucked around with this message at 18:44 on Oct 23, 2015 |
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Oct 23, 2015 18:41
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Saw a fun one a while ago. Woke up to a loud *BOOOOOMMMMMMMNNNNK* sort of a noise and then the power went out. It was only about 30min before I was supposed to wake up so I said gently caress it and got ready for work in the dark. On the way out of my neighborhood I find a natgrid truck, a couple very confused HV electricians, and a police cruiser plus a lot of traffic cones. What was probably a 4160 line had abruptly decided to melt in half about 3 feet from a pole, one end lying on the ground, the other just sorta hanging/sticking outward. I asked the nearest electrician what might have caused a single phase failure that far from the pole and he just shrugged and goes "not a fuckin' clue, man." Zero charred squirrel corpses, no vehicle wrapped around the pole, no tree branches near it... NFI. They spliced it back together, turned everything back on, and that was that.
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Oct 23, 2015 19:07
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angryrobots posted:In other news, this happened to me Tuesday: What voltage level is that? 4160?
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Oct 26, 2015 01:04
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7200/12470 wye Although, because of the switching operation we were performing, tying together two circuits one phase at a time, both electronic reclosers had ground trips blocked. No non-reclose either. Between that and the short distance to the substation, the arc flash would have been substantial, whether it went phase-phase or phase-ground. Probably best case scenario would be phase-phase, you'd still get an operation out of the recloser on a short curve, and if it was that tap just below, then hopefully the fuse would clear it before anther operation. Expulsion fuse which you don't want to be under, but still better than arc flash on the delayed time curve. angryrobots fucked around with this message at 05:06 on Oct 26, 2015 |
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Oct 26, 2015 04:33
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angryrobots posted:7200/12470 wye Do you guys not have a set up for work on your reclosers? I know for the line guys, when they need to work, we switch reclosers to instant trip and no reclose. Not 100% sure if we do that for guys closing manual switches.
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Oct 26, 2015 10:10
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TheFargate posted:Do you guys not have a set up for work on your reclosers? I know for the line guys, when they need to work, we switch reclosers to instant trip and no reclose. Not 100% sure if we do that for guys closing manual switches. Live line work should have fast trips on your reclosers with reclose disabled, but closing an ABS doesn't usually require it. That engineer who wanted to keep switching after a near fatality switch failure needs to be reported to the local board or safety authority that is not cool. Disabling SEF to parallel lines can be standard, but turning off all earth fault protection is nuts. edit: I hope someone at your company is investigating this, because if that model of switch failed and you have a lot of them its a matter of time before it happens to someone else. slorb fucked around with this message at 12:36 on Oct 26, 2015 |
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Oct 26, 2015 12:32
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slorb posted:Live line work should have fast trips on your reclosers with reclose disabled, but closing an ABS doesn't usually require it. That engineer who wanted to keep switching after a near fatality switch failure needs to be reported to the local board or safety authority that is not cool. For the record, I completely agree with all of this. Im not entirely sure what our procedure is for closing those types of switches as I work on the construction end rather than the maintenance end.
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Oct 26, 2015 16:54
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TheFargate posted:Do you guys not have a set up for work on your reclosers? I know for the line guys, when they need to work, we switch reclosers to instant trip and no reclose. Not 100% sure if we do that for guys closing manual switches. Just to cover up, not moving anything, only ppe is required. No non reclose enabled. Working with a hot stick, from outside of the MAD, does not require non-reclose, but in -our- case, is limited to operating switches, or removing/installing equipment via hot line clamp. slorb posted:Live line work should have fast trips on your reclosers with reclose disabled, but closing an ABS doesn't usually require it. That engineer who wanted to keep switching after a near fatality switch failure needs to be reported to the local board or safety authority that is not cool. OK, so I'm a lineman not a relay tech so bear with me and my probably incongruous explanation. We are told that in this specific situation (tying or breaking two circuits together via single switches, one at a time), SOP is to disable ground trip on both reclosers, because the controller could misread the shift of load on a single phase as a fault, and open up. Is this not SOP across the board? It would not surprise me in the LEAST if this procedure of ours, is a holdover from 40+ years ago with mechanical relays, and even then of questionable merit. If this is not common, why is the ground trip block shortcut button right there up front on every electronic controller? What is its usual purpose? angryrobots fucked around with this message at 21:11 on Oct 26, 2015 |
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Oct 26, 2015 21:08
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angryrobots posted:You mean working past (as in downline) of a recloser? Yeah, if we're both working inside the minimum approach distance, and moving anything hot, we set whatever maximum safety we can get. Non reclose, or hot line tag (faster curve, non reclose) if available. And I say "we set" because we do not have any SCADA, so everything is manual on-site. I have never heard of disabling the protection to close a switch.
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Oct 26, 2015 21:56
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angryrobots posted:
If you're paralleling radial feeders with open delta regulators on them you will have an induced loop of zero sequence current which will often trip the sensitive earth fault protection unless the regulators are locked at neutral tap. Another situation that can trip recloser SEF is a bad (resistive) connection on one phase of a non-ganged switch close leading to unbalanced load on that phase. I believe this is the one you're disabling the recloser EF for. If your protection guys know what they're doing you shouldn't have all your recloser EF protection pick ups low enough to require disabling it entirely on the recloser though, the whole point of SEF is its set low and slow so you have it as a backup under normal operation. I hope the button you're talking about just disables SEF. slorb fucked around with this message at 04:43 on Oct 27, 2015 |
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Oct 27, 2015 04:40
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So I just found out what our procedure is. 90% of the time they just phase across and close the switches. If they do anything, they disable reclosing and leave the TOC in place.
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Oct 27, 2015 14:10
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slorb posted:If your protection guys know what they're doing you shouldn't have all your recloser EF protection pick ups low enough to require disabling it entirely on the recloser though, the whole point of SEF is its set low and slow so you have it as a backup under normal operation. I hope the button you're talking about just disables SEF. OK so a clarification. I asked our one guy (yes we have over 4k miles of distribution and 30k customers, with the absolute bare minimum of employees but I digress) and while he did not use the term sensitive earth fault protection, it may be exactly that. I was wrong about the setting we were using disabling phase overcurrent protection - those curves remain active and are faster than what we ARE disabling. So, that's cool and I'm glad to know that. Our lack of understanding about this on the maintenance side, is probably related to "need to know", keep it simple like. The curve that we are disabling during circuit paralleling, he continues to refer to as ground fault. He said ground fault is a calculated value, and that the potential problem comes in when circuit load becomes unbalanced. As I understand it, their concern is that enough of the load will shift during the time it takes to operate these single switches, that this slow curve will cause an operation.
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Oct 27, 2015 20:44
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angryrobots posted:OK so a clarification. I asked our one guy (yes we have over 4k miles of distribution and 30k customers, with the absolute bare minimum of employees but I digress) and while he did not use the term sensitive earth fault protection, it may be exactly that. Huge props to that guy who does all your protection, doing protection work on your own is scary poo poo. Yeah if you're closing in one phase at a time to a parallel feeder (especially one fed from a remote substation) and there's a big enough difference in impedance to the substation(s) on the different feeders you'll get unbalance current that will trip the feeder on earth/ground fault. If you're just disabling the slow extra sensitive earth fault curve that makes sense. The reason I was concerned is if you're disabling all residual (earth fault / ground fault) protection on the recloser on a 12kV feeder it is unlikely your phase fault OC setting can be low enough to pick up on high impedance ground faults like conductors hitting a tree or a line down on crap sandy soil unless its a very lightly loaded line.
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Oct 28, 2015 09:03
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This week sucked. I issued settings for a new substation with two busses protected by separate 487B relays and the field couldn't load the 487B settings due to the firmware mismatching. Oops I'm an idiot, I update the firmware to the version listed in the bill of material. Field still can't load the settings due to firmware mismatch. After way too much back and forth, I give up and request pictures of the relay LCD. The north bus relays were ordered with the firmware version as per the BOM while the south bus relays were ordered with the latest firmware. 
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Nov 7, 2015 04:46
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freezepops posted:This week sucked. I issued settings for a new substation with two busses protected by separate 487B relays and the field couldn't load the 487B settings due to the firmware mismatching. Oops I'm an idiot, I update the firmware to the version listed in the bill of material. Field still can't load the settings due to firmware mismatch. After way too much back and forth, I give up and request pictures of the relay LCD. The north bus relays were ordered with the firmware version as per the BOM while the south bus relays were ordered with the latest firmware. Legit question, do you not require 2 person verification of programmable field constants and other critical firmware software? I mean this is something I do at work, managing firmware and software for key systems and I don't see how this could have happened. Also did the vender for the south bus not follow the documentation specs for your constants?
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Nov 7, 2015 18:42
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Someone just forgot to specify a firmware version for the south bus relays when they were ordered, so the manufacturer shipped the latest version. When it comes to settings we just require the field or construction crew to send as left settings. This would include information about the FID, settings, part number and everything. Eventually when everything is put into service there is record of all that stuff, however when the panels are still being assembled my only reference is what the design bill of material states.
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Nov 7, 2015 21:25
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Step 1 of my job is to pull firmware relay info to send to the protection guys to write the settings. Typically they write the settings after receiving said info. Also I have not used a 487B, we mostly use 487Es for transformers. Are the Bs anything like a 587z? Thats what we use for bus protection 99% of the time.
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Nov 7, 2015 22:03
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The 487B is bus current differential, so its style of protection is more like the 587 non-z. The main advantage of the 487B over a 587 is the 21 current inputs and the ability to have multiple current differential zones that can separate/change based on the SELogic.
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Nov 8, 2015 00:33
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freezepops posted:The 487B is bus current differential, so its style of protection is more like the 587 non-z. The main advantage of the 487B over a 587 is the 21 current inputs and the ability to have multiple current differential zones that can separate/change based on the SELogic. Thats pretty cool and also explains why we use 587zs. My company tends to use 1/10th (if that) of what SELs can do. So they probably go with the 587z for simplicity.
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Nov 8, 2015 17:41
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Hello! Reading a lot of this thread, there's a lot in common EE has with communication and audio engineering. Specifically, analog and digital signal processing. Although, square waves/clipping and overloads are a bit different in physical/analog electrical devices and digital signal processors! For instance, a physical speaker receiving a signal of higher amplitude than it can handle, will be damaged. If the signal is converted from a digital signal, it's limited (hard) and generates unpleasant sound which, after sustained generation, may cause damage but not as quickly as a transient from a system without limiting circuitry or other factors.
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Jan 3, 2016 02:46
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Some time in the 1920's/1930's, Germany decided that their railways were going to run on 16 2/3 Hz power, more or less fed by an entirely separate grid. What would be some good reasons (back then) for that?
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Jan 7, 2016 21:05
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original sin
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Jan 7, 2016 22:25
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Probably resulted in the desired RPM at the motor, without needing to implement a variable frequency drive on the train or anything like that.
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Jan 8, 2016 04:17
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IOwnCalculus posted:Probably resulted in the desired RPM at the motor, without needing to implement a variable frequency drive on the train or anything like that. Pretty much this. We have generators that actually take 60hz and and slow it down to 30hz (IIRC) for the railway.
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Jan 8, 2016 13:25
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Wikipedia’s article on “Amtrak's 25 Hz traction power system” is extensive, if you’re interested.
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Jan 8, 2016 13:35
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I've also seen these really wacky converters where you have a doubly-fed induction machine and a DC motor that spins the rotor. AC input comes in on the rotor, AC output at different frequency and voltage is from the stator, and you can get a wide range of voltages and frequencies that are pretty much pure AC. Drawbacks are the fact that you need a big DC motor and drive to spin the thing, and it cannot operate at 60Hz output because then it isn't rotating any more and the slip rings on the rotor will burn. Three-Phase fucked around with this message at 15:03 on Jan 10, 2016 |
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Jan 10, 2016 15:01
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nielsm posted:Some time in the 1920's/1930's, Germany decided that their railways were going to run on 16 2/3 Hz power, more or less fed by an entirely separate grid. A particuarly sturdy DC motor can be run on AC power up to 18Hz. And if you think that this was the dumbest thing you could do with this system be prepared for a shock
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Jan 15, 2016 14:59
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homebrew posted:A particuarly sturdy DC motor can be run on AC power up to 18Hz. And if you think that this was the dumbest thing you could do with this system be prepared for a shock  I think that's the craziest thing I'll read today.I assume you mean a series-would DC motor, although it would be interesting to see someone try that with a permanent magnet motor.
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Jan 15, 2016 16:02
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Frozen Horse posted:
Yeah, and that is what they did.
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Jan 16, 2016 06:09
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In Sydney, the train network was first electrified in 1926 and runs on 1500v DC - since DC motors offered greater torque/speed at the time. In the 1970s, when new lines were expanded they toyed with the idea of 25KV AC conversion due to advances in AC motor technology - but was deemed too costly. So now we are stuck with outdated technology. *sigh*
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Jan 27, 2016 22:54
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Lots of urban rail runs on DC? Even brand new metro systems are designed for DC.
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Jan 27, 2016 23:14
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Big Steveo posted:In Sydney, the train network was first electrified in 1926 and runs on 1500v DC - since DC motors offered greater torque/speed at the time. They would have to replace most of the infrastructure above the rail head; including but not limited to feeders, catenary, sub stations, supply lines, switching equipment and control. You would also need to be able to retro-fit the current rolling stock to be able to run on both 1500VDC and 25KVAC to allow operation during the change over. For a suburban electrification system, there is little that a 25KVAC system that the 1500VDC system can not do. If NSW were to do some serious country electrification, a new rural 25KVAC system with multi-voltage loco's or EMU's would be the way to do it homebrew fucked around with this message at 14:31 on Jan 30, 2016 |
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Jan 30, 2016 14:28
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Anyone have any experience with conductive grease for corrosion inhibition inside control panels? We're evaluating the use of something like that in our panels on ground bars/lugs/etc. The main problem being that when you scrape the paint away, you open up the subpanel/enclosure to corrosion. One of our senior engineers is recommending we move towards galvanized subpanels for that reason, but I would think that there will still be some remaining issues. Ideally we're looking for something conductive so we can use it on all exposed surfaces and not worry about connection issues. We've come across 2 options: T&B Kopr-Shield and Sanchem NO-OX-ID . Anyone have experience with either of these? Kopr-Shield is UL listed, so we're leaning towards that one. However in researching this I keep seeing NO-OX-ID come up as a more commonly used option. The other question is, is NO-OX-ID actually conductive? The meter says no, but I don't know if that's really a valid test.
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Feb 8, 2016 15:02
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DaveSauce posted:The other question is, is NO-OX-ID actually conductive? The meter says no, but I don't know if that's really a valid test. Wire it to a bench supply at a reasonable voltage and meter off that.
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Feb 8, 2016 15:23
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DaveSauce posted:We've come across 2 options: T&B Kopr-Shield and Sanchem NO-OX-ID . This might be a really stupid question: Does your insurance require UL listing on safety components? (Grounding bus bars.) Smearing them with non-UL goo might change that.
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Feb 8, 2016 16:46
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We used NO-OX-ID on all the breaker-bus contact points. Pretty sure if you have a thin layer between your copper its very conductive.
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Feb 8, 2016 17:56
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We're a machine builder, and this is going in to a panel for a customer, so our insurance has no bearing on this. We occasionally UL list our panels, but I don't believe UL508A addresses this. I do know that NEC addresses it, but I think the only application NEC cares about is protecting the threads on field threaded conduit. I don't know if its use on bus bars/ground lugs/terminals is considered at all. This came up because another engineer is particularly concerned about an application that will be near the ocean. The enclosures are stainless, but the subpanel is painted steel. Our panel shop always scrapes the paint for ground bars/lugs, but they never seal them with anything. The panel shop at my last company always put some sort of goop on to protect the bare steel, but that was a shop standard so I never knew what they used...it just happened and I took it for granted, so now that I'm at a place that doesn't do that I have to re-invent the wheel. That said, all else equal, I would personally pick the UL listed version over the non-UL version. So that's where we're at: are these in fact equivalent products, or do they each have their place?
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Feb 8, 2016 21:45
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Compact Inverter Challenge winners got announced today: http://googleresearch.blogspot.ca/2016/02/and-winner-of-1-million-little-box.html The details PDF's from each team are very readable https://www.littleboxchallenge.com/
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Mar 7, 2016 17:33
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