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angryrobots posted:High voltage transmission lines are usually not as affected because they usually have much wider right-of-way, but they hit the dirt sometimes too. Everything in line work is temporary. January 1998, never forget  
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Sep 11, 2014 01:20
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angryrobots posted:Another example of failed fault protection from the OSHA thread : So is staring at that while it's arcing as dangerous as welding w/out eye protection on?
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Sep 11, 2014 02:36
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Yes.
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Sep 11, 2014 04:12
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Jyrraeth posted:However, I don't really know what's going on in a more technical sense. Does the power company have a controller somewhere that can see which lines are down? Or which breakers have tripped? Is there anything special when you're trying to fix a whole city while the whole province is hosed up? There's no trees close to anything high power in the substations but would high power lines be affected? There are a variety of ways we can tell the lights are out, but the number one way is still via customers phoning in. Many utilities have also installed smart meters at customers homes, which will automatically broadcast a loss of power condition which a control centre would use to dispatch crews. SCADA devices like reclosers will also provide tripping indication, and most substations have at least basic SCADA control and indication. I've seen some presentations by big southern US utilities demonstrating how their control centre will actually try and predict the path of a storm to try and dispatch crews where they're going to be needed. It's pretty cool, but requires a lot of sophisticated models and state simulation of the transmission and distribution systems. Some of these models will actually provide distance to fault values (based on fault current, prefault conditions, line impedance, and some other black magic), calculated by the control centre software. I've seen one with a ~10% error, which can help a huge amount when your linemen are driving 100kms of distribution line in the middle of the night.
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Sep 11, 2014 04:42
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We have smart meters, and they only can work as well as the hub located at the sub station... In a large outage we usually lose communication with the hub so it's phone outage management. They can be useful during smaller outages or like a thunderstorm with scattered calls, but in my experience they have us chasing a bunch of accounts that aren't even off. Easy overtime tho'.
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Sep 11, 2014 12:51
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thylacine posted:So is staring at that while it's arcing as dangerous as welding w/out eye protection on? If not more dangerous. That's a hell of a lot more voltage and therefore a hell of a lot more current and power being jammed into a similar sized spot, you're going to get much more energetic UV out of it. In fact welding and similar intense arc sources of light are one of the few ways you can be exposed to UV-C (between UV-B and X-rays on the spectrum) while remaining inside the earth's atmosphere.
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Sep 11, 2014 19:43
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angryrobots posted:Another example of failed fault protection from the OSHA thread : I actually managed to find a news article about this event years and years ago. There was a crew out trimming trees. They hosed up good. If you watch the video long enough (or enough segments), there's a guy still up in the bucket saying (basically) "GET ME THE gently caress OUT OF HERE". 30 kV suddenly being fed into a 7.2kV or 13kV line will probably gently caress up the transformers along the way bad enough to send the full 30kV along, I would think? Even if it doesn't, you're still feeding thousands of volts into a household electrical system designed for 120/240V, with wiring that's probably not rated past 300.. MAYBE 500 volts. Killamajig posted:There are a variety of ways we can tell the lights are out, but the number one way is still via customers phoning in. A couple of years ago, I was living in university housing. There was a decent storm, and I noticed that there was a lot of arcing at a nearby power pole at the disconnects (basically about 100 ft from my car  and juuuust off of university property), along with my own lights flickering pretty badly (went off a couple of times, then came back on).Tried calling the local power company; their automated system wouldn't let me report an issue without an account number or registered phone #, and mashing 0 just got a "invalid selection" followed by being hung up on every time I tried (every other option just got a "invalid account number" or "I don't recognize your phone number", also followed by being disconnected). I guess their system actually logs that kind of stuff; someone called me back a few minutes later and said they'd noticed I'd tried to report an issue, but that my phone # wasn't registered to an active account. Explained the issue, they had someone out there within 10 minutes. Still no idea what was causing it, but they did open a disconnect on the line. I'm glad their automated system was smart enough to recognize "hey, someone's trying to report something, but they can't register an issue because they don't have an account with us, maybe we should call them back?".
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Sep 14, 2014 09:46
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some texas redneck posted:I actually managed to find a news article about this event years and years ago. Yeah I saw the bucket still in the air at the beginning, and racked up later, so maybe dude made it down OK. Lucky he was far enough away the bucket hydraulics weren't compromised. There was a situation a couple years ago where a lineman was working in the bucket, and the digger truck hit a gas main directly below him with the auger, and immediately caught fire. He couldn't get out of the way quickly enough, bucket wouldn't move, tried to jump but didn't disconnect his harness and hung there and burned until the harness lanyard burned in two. some texas redneck posted:30 kV suddenly being fed into a 7.2kV or 13kV line will probably gently caress up the transformers along the way bad enough to send the full 30kV along, I would think? Even if it doesn't, you're still feeding thousands of volts into a household electrical system designed for 120/240V, with wiring that's probably not rated past 300.. MAYBE 500 volts. So the short answer is no, not immediately. I suppose eventually something could fail and who knows how. As to the house wiring, I thought romex was tested for 600v? Seeing what I assumed was the soffit lighting circuit blowing up around the eaves of the house, I would think it would take a few thousand volts to compromise the insulation along the entire length of the run like that.
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Sep 14, 2014 15:12
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It also depends on the equipment connected - I'm sure very little end-user equipment designed for 120/240V will operate safely at, say, 600V because at the higher voltage the gaps aren't large enough. This wasn't a spectacular explosion, but I had 120V powered instrumentation that was crashing because of capacitor bank switching transients that briefly brought the voltage from 170V peak to like 240V peak for about one cycle. That wasn't a severe transient.
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Sep 14, 2014 21:00
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Oh yeah even if the transformer held up, I'm sure every device connected world be burned up if exposed to voltage much higher than designed for, but I think the conductor for the circuit around the eaves of the home (Romex I'm assuming) would not fail that spectacularly unless exposed to much higher than 600v. And it could very well be that the transformer insulation eventually failed and from that point primary voltage found its way to the service wire any number of ways.
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Sep 14, 2014 21:17
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some texas redneck posted:A couple of years ago, I was living in university housing. There was a decent storm, and I noticed that there was a lot of arcing at a nearby power pole at the disconnects (basically about 100 ft from my car If only there were a three-digit number you could call to report any type of emergency... angryrobots posted:but I think the conductor for the circuit around the eaves of the home (Romex I'm assuming) would not fail that spectacularly unless exposed to much higher than 600v. Was there necessarily a circuit there? Or could it have been gutters or metal paneling or something?
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Sep 14, 2014 23:06
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squeakygeek posted:If only there were a three-digit number you could call to report any type of emergency... I would try the utility directly if you are sure about who it is, before calling 911. squeakygeek posted:Was there necessarily a circuit there? Or could it have been gutters or metal paneling or something?
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Sep 15, 2014 00:11
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angryrobots posted:To be fair, some counties may have lines belonging to four or more utilities, and emergency services has no idea what belongs to whom. There can be some delay, especially if they call the wrong utility, have someone ride out there just to say "nope, not our problem". This was a city co-op. I didn't think the situation warranted a 911 call; it was arcing, but not severely, and nowhere near ground level. The utility handled it pretty quickly. I've called 911 before about a leaning power pole, with lines hitting each other every time the wind kicked up, knocking out power to my apartment complex for a few minutes each time. They shrugged when they saw it and said to call the utility. The utility shrugged and said it was on apartment property (it wasn't, it was in the alley just off the property), and didn't get around to fixing it for nearly a week - and their fix was to put insulators on the wires. When I moved out a year later, the pole was still leaning.  (it had been struck by a car in the alley at some point) This was in a different city (Dallas), with a large for-profit utility owning it (Oncor).
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Sep 15, 2014 03:14
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Any advice on useful certifications for working on VFDs and motor control systems? As far as experience goes, what are employers generally looking for when it comes to networking protocols and PLC brands?
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Dec 14, 2014 17:29
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Everything is a lot closer together up here in CT, but I've never had a problem calling the non-emergency police number in case of utility line problems and telling them there's something wrong with a utility line and I'm not sure whether or not it's a safety concern. For an arcing line that's obviously a safety risk I would call 911 because they have a direct line to all the utilities.
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Dec 15, 2014 18:42
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The talk about power lines to Mars reminded me, are power lines typically long enough that transmission line theory is needed to design the network wrt. disconnecting lines, transformer impedances and such? I don't know what kind of impedance a long high voltage line would have, but if a sufficiently long line was opened suddenly at the load then power could be reflected and cause some issues right? I realize a 60 Hz transmission line would have to a significant fraction of the earths diameter to be long enough... Is phasing of the power a problem when load sharing between power plants far away/near a load? North America would be large enough that a 60 Hz signal would have some phase shift if all power plants just synchronized their generators to a common timebase, are there "master" plants that decide the operating frequency and smaller plants phase lock onto the incoming power from other plants?
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Jan 6, 2015 17:28
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Only a few small plants control frequency and the rest sync to that. Generator excitation plays a very important role in damping the low frequency oscillations between plants. From what I have heard the inductive reactance of a long line is enough that you cant just dump a generator on it without tripping. You have to energize smaller segments together before connecting a long line.
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Jan 7, 2015 02:41
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I can't speak for the gen side since I have not really done much work in those. But I may be able to help from a transmission/distribution view. AFAIK, most of our frequency based protection is on our 13kV systems. Once a gen becomes so bogged that frequency starts to drop, our system will automatically start shedding load of non essential customers. Our system actually played a big role in preventing the spread of the 2003 NE US blackout. Our system starts to shed load once frequency drops to about 59.8 Hz. As for energizing long transmission lines heres the gist of how thats typically done: All loads are disconnected from the line. Then, ONLY voltage is applied to the line. If its a new line they may or may not let it "soak" before applying load. Once its decided that its ok to go into service, load is generally applied one station at a time. As far as how quickly we can start adding/subtracting load, well that depends on whatever PJM/our system operators decide. Shoot me a PM if you have any questions, I can try and dig up some impedance numbers and what not.
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Jan 7, 2015 14:13
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Time to play "guess the facility" oil rig They want to build a 10-MW PV array adjacent to help bring down utility costs. 
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Jan 8, 2015 19:35
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Will it be worth the investment?
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Jan 9, 2015 00:31
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It's not my project so I don't know the exact numbers, but I think it will be yeah. They own the land already, it's in the middle of the desert with absolutely ideal solar conditions, and I think they expect it to offset 1/2 to 2/3rds of their energy use.
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Jan 9, 2015 22:42
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Stupid question, but the following building is right near property I'm interested in buying. I'm assuming this is water treatment, not electric power?
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Jan 14, 2015 08:20
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Definitely not a power station.
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Jan 14, 2015 09:39
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The Cleaner posted:Stupid question, but the following building is right near property I'm interested in buying. I'm assuming this is water treatment, not electric power? Illuminati chemtrail juice storage tank. Trespass and refuse to leave until they prove its not going to be used to mind control the American public. Let us know which channel to watch. 
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Jan 14, 2015 20:40
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whoops
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Jan 14, 2015 22:38
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The Cleaner posted:Stupid question, but the following building is right near property I'm interested in buying. I'm assuming this is water treatment, not electric power? The barbed wire looks like it's facing inwards; what are they trying to keep from escaping? 
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Jan 15, 2015 04:36
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killhamster posted:The barbed wire looks like it's facing inwards; what are they trying to keep from escaping? kastein posted:whoops We're through the looking glass here people....
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Jan 15, 2015 19:14
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I have a question for anyone here that does line protection relaying or really anyone who has knowledge of creating protection settings. Im working on writing some macros in doble protest and there are some functions I am trying work into it. The relays that I am testing are SEL311Ls and GE L90s. Basically once a relay is installed its my job to make sure it functions. They give me a sheet of values that, for example line relays, should each trip the relay in different zones in step distance. What Im trying to figure out is how they actually come up with the current and voltage values. I know its based on CT/PT ratios along with line impedance. Which are all values I am given. My question is how do I get from impedance and nominal values to these drat test values? Ive tried all sorts of math from ohms law to vector addition and every combination of them I could think of. If anyone could give me a bit of insight it would be much appreciated.
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Jan 22, 2015 17:24
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I imagine you know this already, but all of our trip values are based on coordination, so up and downstream protection works as intended. The manufacturers of protection devices (whether a fuse, hydraulic recloser/sectionalizer, or electronically controlled device), provide tables with all the information about how a device is supposed to perform (time delay curve), and in some cases, what other devices should or can perform up or downstream from it. Maybe the values you are given aren't based on a calculation but the coordination scheme that the engineer came up with, to work with other protection devices on the line? Edit: I'm sure you know more about this than me, and this isn't answering your question. :p
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Jan 22, 2015 18:58
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Thanks! but I already know about that stuff lol. Basically we have a department dedicated to developing all the settings for relays based on coordination, circuit load and impedance. So honestly what Im doing is a little outside my job description lol. What I guess I am trying to figure out how to use the impedance magnitude and angle to actually calculate the boundaries of each zone of protection. For instance: what should my zone 1 minimum pickup value be? My maximum? What value is the boundary between zone 1 and 2? Etc etc etc. But thanks!
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Jan 22, 2015 19:18
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TheFargate posted:Thanks! but I already know about that stuff lol. Basically we have a department dedicated to developing all the settings for relays based on coordination, circuit load and impedance. So honestly what Im doing is a little outside my job description lol. What I guess I am trying to figure out how to use the impedance magnitude and angle to actually calculate the boundaries of each zone of protection. For instance: what should my zone 1 minimum pickup value be? My maximum? What value is the boundary between zone 1 and 2? Etc etc etc. But thanks! The rule of thumb that I have heard and the one that I have used for setting impedance relays (also called distance relays) is to set Zone 1 to 80% of the line impedance and set Zone 2 to 125% of the line impedance. Zone 1 is set instantaneous and will protect faults on the majority of the line (set less than 100% to avoid unintentional overreach due to error in the line model, error in the CTs and VTs, and error in the relay calculations). Zone 2 is delayed (may use a DCB scheme for faster tripping with a slower backup on receipt of block) and protects faults on the entire line with (set to more than 100% to avoid unintentional underreach due to the same errors as Zone 1). The Zone 2 setting may need to be reduced in case the adjacent transmission line is a short line, as the 125% setting is meant to reach past the protected line and into the adjacent line, but you wouldn't want it to reach past the adjacent and into a third line. Also, the rule of thumb is for a two terminal line; three terminal lines and lines with tapped loads become much more complicated. Protective Relaying by Blackburn is a great resource for relaying. You should be able to take the Zone 1 and Zone 2 set points that you have, convert them from secondary Ohms to primary Ohms (using the CT and VT ratios) and then compare that to the impedance of the protected line (in actual Ohms, you may need to convert from per unit if that is how the model spits out the values). I'm guessing you will find that Zone 1 is about 80% and Zone 2 is about 125% unless you are in a special case (e.g. three terminal, tapped loads, or short adjacent line). Protective relaying is one of my favorites parts of being a power systems engineer, so I would be happy to elaborate more, if I didn't answer your question completely. I've lurked this thread for a while, but never got around to posting before. I spent five years as a consultant doing substation design for wind farms, solar farms, and data centers; one year blowing stuff up in one of the most powerful short-circuit labs in the US ; and am now doing substation relaying and commissioning work for an oil utility. If anyone has questions in any of those areas, I would be happy to share.
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Jan 23, 2015 04:01
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The Cleaner posted:Stupid question, but the following building is right near property I'm interested in buying. I'm assuming this is water treatment, not electric power? jjack229 posted:I've lurked this thread for a while, but never got around to posting before. I spent five years as a consultant doing substation design for wind farms, solar farms, and data centers; one year blowing stuff up in one of the most powerful short-circuit labs in the US I think I speak for most goons when I say I'd also like to hear about the time you spent blowing stuff up. GWBBQ fucked around with this message at 04:18 on Jan 23, 2015 |
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Jan 23, 2015 04:13
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GWBBQ posted:Are there any big differences between designing substations for different types of generation? The PV plants I worked on (5 - 20 MW) were smaller than the wind farms (80 - 120 MW) so there were differences just due to the size. Of course, these are both tiny compared to traditional plants (e.g. coal, or hydro, or nuke), but I didn't work on any of those. The collector systems (the cables from the turbines/inverters to the substation MV bus) are significantly different. The PV panels and inverters are all next to eachother in a one large fenced-in area. However, the wind farms are spread out of large distances all over farmers' land. My 90 MW project had 50 turbines and had 47 miles of trench to bring that back to the substation. The turbines were consolidated into four feeders, so that is 47 miles of trench with the turbines daisy-chained, not a single feed from each turbine directly to the substation. A big difference from the relaying side, is that wind turbines are spinning machines, so in the event of a fault they can source fault current since they are converting some of their rotational kinetic energy into electrical energy. However, PV solar is inverter-based so they have extremely limited ability to source fault currents (basically they provide full load current even for a bolted fault). This affects the protection elements used on both the MV and HV sides of the substation to properly detect faults. Also, the wind farm industry is much more mature than the PV industry. It is very apparent when looking at the owners/developers, but also the utilities and ISOs are still working out the interconnect requirements for PV. I've seen quit a few wind farm substations and they all follow the same basic design; high-side breaker, main power transformer, low-side bus with outdoor feeder breakers and grounding transformers. But I've seen a lot of different PV substation designs, in part due to the smaller size, but also everyone just trying to push their lowest cost option (outdoor breakers, metal-clad gear, metal-enclosed gear, padmount gear, reclosers, some weired combination of these, etc.). In all honesty, most of the time in the lab wasn't blowing stuff up (or at least they weren't supposed to blow up). A lot of the testing we did were things like fault interrupting, short-circuit withstand, and load interrupting testing. Not only was seeing/hearing/feeling the test cool, but we also had a high-speed camera (2000 fps). It is amazing to see how flexible metal is when subjected to high current/forces and viewed at high speed. We also did a lot of power fuse testing. Mostly 15 kV fuses (sounds like a gun when it goes off), but a couple of 35 kV fuses (sounds like a canon when it goes off), and even a 69 kV fuse (not as loud as the 35 kV, but it was tested at reduced currents due to the current/voltage limitation of the generators). We also did some internal arc fault testing, which is ridiculous to see. We did some for padmount interrupter gear, which was neat, but the coolest ones was for a set of 15 and 25 kV custom metal enclosed indoor switchgear units. They were tested to the indoor arc fault standard, so backed into a corner with a false ceiling hanging over it and then flammable cloths all around the gear (if the cloth is burned, the unit fails the test). The test was 25 kA at ~15 kV (enough to sustain the arc) for 1 second. I've been involved in arc flash hazard calculations, had training on arc flash PPE, and seen videos, but I still wasn't prepared for how much energy is released in those arc fault tests. It furthered my respect for lineman and for arc flash safety. Below is a GIF that I quickly put together from a fuse successfully clearing fault current, I think it is 10 kA at 15 kV. I think it is really cool to see the fireball come out in slow motion. 
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Jan 24, 2015 23:43
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should I drop in to school and do this poo poo or drop out of school again and do this poo poo again
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Jan 24, 2015 23:50
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jjack229 posted:Words This is awesome and helps a lot. Pretty sure I know exactly where I messed up now. While I multplied by ct/vt ratios to for current/voltage values I completely forgot to use my primary line impedance lol. So then my next question is this: through the use of my line impedance along with a Mho circle, how do I calculate actual test values so when I test a relay I can prove the limits of say, zone 1? I have found the equation Z = (Ex - Ey) / (Ix- Iy) but what do I need to do to actually solve and come up with voltage and current values? Thanks man!
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Jan 26, 2015 19:27
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jjack229 posted:Below is a GIF that I quickly put together from a fuse successfully clearing fault current, I think it is 10 kA at 15 kV. I think it is really cool to see the fireball come out in slow motion. Got any more of this sort of thing? Pretty awesome watching it go off over and over.
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Jan 26, 2015 22:09
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From another thread:TheFluff posted:Thanks to a certain benefactor (let me know if you want credit) I got to visit Ågesta nuclear power plant today. It was the first commercial nuclear reactor in Sweden and was (commercially) active 1964-1974. During those years it was used to produce the only few kilograms of plutonium that was ever produced for the aborted Swedish nuclear weapons program. It's technically a civilian plant, but it's cold war as gently caress.  His caption claims these are 6kV exposed busbars.
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Jan 27, 2015 05:08
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TheFargate posted:This is awesome and helps a lot. Pretty sure I know exactly where I messed up now. While I multplied by ct/vt ratios to for current/voltage values I completely forgot to use my primary line impedance lol. So then my next question is this: through the use of my line impedance along with a Mho circle, how do I calculate actual test values so when I test a relay I can prove the limits of say, zone 1? I have found the equation Z = (Ex - Ey) / (Ix- Iy) but what do I need to do to actually solve and come up with voltage and current values? Thanks man! To test any given impedance, you'd need a combination of current and voltage (both magnitude and relative phase angle) that would give you that impedance. While any values with that fixed ratio would work, you'd be limited on the upper-end by the test set and relay capabilities and on the lower end by the relay sensitivity (I believe the SEL-311 series has a minimum current setting as well for the impedance elements, so you'd need to be above that). If you are trying to simulate actual system conditions, the values would need to come from a system model, since the current would be a function of the sources behind each relay. So, for a fault half way into the line, both line relays will calculate the same impedance, but the relay with a stronger source will see a higher current (and correspondingly higher voltage). I'm not sure what values automated test set programs use to test out the mho circles, but for any given value that you want to test, you should only need the combination of current and voltage. If your Zone 1 is set to 1 Ohm @ 70 deg, then if you apply 14.25 V @ 0 deg and 15 A @ -70 deg (impedance of 0.95 Ohm @ -70 deg) it should trip on Zone 1. If you apply 15.75 V @ 0 deg and 15 A @ -70 deg (impedance of 1.05 Ohm @ -70 deg) , it should NOT trip on Zone 1. The relay may require some pre-fault voltage before the fault current and voltage are applied (in part to drop out and undervoltage or loss of potential elements, but also because some relays will use a memory function from the pre-fault voltage waveform for when the fault voltage is very low). It's been a while since I've used a test set on a directional relay, but I think that is most of the steps. H110Hawk posted:Got any more of this sort of thing? Pretty awesome watching it go off over and over. I have a few more videos that I can sort through and make some GIFs from.
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Jan 28, 2015 04:40
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jjack229 posted:(I believe the SEL-311 series has a minimum current setting as well for the impedance elements, so you'd need to be above that). This is exactly what I need to narrow down my calculations. I should now be able to throw something together today. Thank you very much! You have been incredibly helpful!
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Jan 28, 2015 11:09
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If you run into more issues I might be able to help by taking a look at our RTS routine for the 311L. Don't have a routine for the 90L, unfortunately.
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Jan 28, 2015 16:51
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