|
Platystemon posted:....Tons of refrigeration...
|
#
¿
Dec 28, 2013 16:31
|
|
|
|
| # ¿ Apr 28, 2024 09:08 |
|
|
Just make sure all panel covers are installed, and figure out why it's tripping. I would like to note however, that all entrance cable which is before your main breaker, is protected only by your utility and is EXTREMELY hazardous. Say you've got a 4/0 service coming out of a 100 kva underground transformer to your house (common in a subdivision). It will take a massive amount of fault current to trip the utility protection. Probably enough to burn the fault in the clear before it trips. In newer houses, they usually install a combination meterbase that has a main breaker. So, this dangerous current potential is limited to this one box outside and everything past the breaker is protected. But in slightly older homes, they would sometimes just have a meterbase outside, feeding a main panel somewhere in the house. The entrance cable from the meterbase to the main is a serious hazard, and in some cases is stretched all across the house depending on where they decided to locate the main panel.
|
|
#
¿
Dec 28, 2013 19:35
|
|
|
Or your work. :P
|
|
#
¿
Dec 29, 2013 06:22
|
|
|
I had a trouble call on a sewage lift station one Saturday morning, electrician said one phase is out. It's a big platform bank, 480 corner ground delta. Their switchgear and breaker panel are inside a fence directly under the platform structure. It is a relatively confined space for them, in front of the panel. I check voltage ok up top, but they still have bad phase to phase on one leg, on the load side of one of their breakers. They decide to reset the breaker. I ask them to let me get set up to pull the fuses up top just in case. He throws it off, then back on, and it starts sizzling like bacon in a pan. He throws it off again, and as I say "I don't think that's a go..." he goes on with it and the back of the panel lights up like an arc welder. I ran out and snatched the fuses as quick as I could. Fortunately no one was hurt, which was luck given their proximity, and the cover plates they had already removed which exposed them further. As I recall, they said the breaker had an internal fault.
|
|
#
¿
Dec 29, 2013 15:41
|
|
|
If you mean the high side fuses, they're at least 150% of kva, maybe more on that bank, and there is a delay curve on all our fuses. Everything in utility protection assumes a fault is temporary and gives time to clear it. Why their fuses didn't clear it, well that's a good question. I didn't get to look at it afterwards, maybe the fault path limited the current somehow.
|
|
#
¿
Dec 29, 2013 18:36
|
|
|
TasogareNoKagi posted:Stupid question! Why didn't pulling fuses on a faulted circuit cause another arc fault in your face? Well, the fuses were 30' above me, I was pulling them with an extendo stick. Also, the fuse holders are loadbreak devices. Sorry, I wasn't clear this was a pole mounted platform bank.
|
|
#
¿
Dec 30, 2013 06:10
|
|
|
I'm a lineman for a distribution utility. Sometimes it's fun but a lot of the time I'd like a job that wasn't so demanding of my time; I'd like being more free to spend more time with my family. And I worry about getting injured with kids I'm responsible for now. Not things I anticipated as a single 22 year old, almost 7 years ago. Anyhow if it's something you're interested in, it will be a lot easier if you're young (I'd say 25 or under really), very fit and healthy, and don't mind working your balls off in all weather. Don't underestimate that last part.
|
|
#
¿
Jan 10, 2014 03:48
|
|
|
atomicthumbs posted:What's the likely cause and effect here: transformer fails, lighting tree on fire and causing voltage sag, or PG&E's system has a brownout, voltage sag causes increased current draw in various appliances, which causes lines to heat up and sag into a poorly maintained tree? 1. Tree gets into primary line on 3 phase circuit. It could have fallen from decay, wind, weather, take your pick but it got into one of the phases. Tree catches fire during arc fault. 2. Circuit protection device opens on single affected phase; utility has 3 individual devices that do not operate simultaneously on all phases. Your home is connected to this phase. 3. The newly open phase is backfed from numerous 3 phase banks connected to the affected circuit. This backfeed does not successfully energize the open phase to full line voltage under load, giving you an undervoltage condition at your home.
|
|
#
¿
Jan 17, 2014 00:35
|
|
|
Hey I was just about to find this thread to post a couple pictures from work, and here it is at the top. Anyway to your question, I suppose if all protection failed then a transformer could melt in some specific situation. I've only dealt with oil submerged pots that exploded. Usually the top blows off as a designed failure point. Something I found, I came here on a scheduled service appointment to take this bank out of service per request so they could work on the electric panels, and found the crew that added another span of wire off the back side of this (previously) dead-end pole had forgotten something very important.. 
|
|
#
¿
Jul 18, 2014 05:20
|
|
|
When the new neutral wire was pulled up, the excess wire never got cut off. You can see it there winding down, laid against the non-grounded x2 wye tie on the primary side, then continuing down through the transformers and laid against one of the tanks near a secondary bushing. The bank was re energized that way. =/ Here's what can happen when re energizing a faulted transformer. 
|
|
#
¿
Jul 18, 2014 18:05
|
|
|
Yeah, assuming there isn't also a mechanical failure in the protection scheme. I worked with our substation engineer a couple years ago testing and adjusting mechanical relays. One of the first tests involves bypassing the main substation breaker, and tripping a relay to test the circuit all the way to the breaker opening. The breaker itself was a oil submersed, spring loaded device 3 phase, 69kv. Anyway, it didn't open. The spring loaded bits were gummed up. If there had been an actual problem inside the protection zone, it world have been a really bad day.
|
|
#
¿
Jul 24, 2014 17:33
|
|
|
The dimming was probably the recloser that protects the circuit that feeds your home, operating because of a fault. The fault could be a local lightning strike, or wind blowing a tree limb into the energized line. On a fast curve, it can be so quick to operate (depending on capability and settings of protective device) that you could see it as a dimming of incandescent bulbs. The line was actually opened for a set amount of time or cycles, and so your digital clocks and router must reset. The reason for this operation, is that most faults are temporary, and given a few operations will clear themselves most of the time, minimizing nuisance outages. Tree limb burns off, squirrel gets blown off line, etc. To the poster that asked about a pot melting -here's one sort of melted? Direct lightning strike to this distribution transformer. 
angryrobots fucked around with this message at 22:55 on Aug 1, 2014 |
|
#
¿
Aug 1, 2014 18:37
|
|
|
14.4/24.9 distribution (the line running down the road) is common to see anywhere, even in residential areas.
|
|
#
¿
Aug 5, 2014 02:25
|
|
|
What electrical career are you looking to get in to? Do you have any field experience, even just general construction? There are several commercial and industrial electricians on here, and I'm a lineman for a co-op power utility.
|
|
#
¿
Aug 27, 2014 02:47
|
|
|
I can tell you too that the linemen message board I follow (mostly for cool pictures) usually tells guys looking to start a career, to not bother with the line schools. If the union is in your area, they usually tell them to "sign the books!" whatever that entails. And I agree with the previous post, my utility doesn't hire 'experienced' workers. It would be better to have any kind of construction experience, something to show you are technical and willing to work in the weather.
|
|
#
¿
Aug 27, 2014 13:15
|
|
|
I'd def try to get an interview. Play up whatever technical experience you have, and that you understand the job is outdoors in all weather, and very demanding. I'm assuming you're in pretty good shape, they probably require a physical prior to employment. They spell out pretty clearly what they want in an applicant: quote:Previous experience in working with mechanical or electrical concepts and applications
|
|
#
¿
Aug 27, 2014 16:57
|
|
|
No a load break tool is a separate attachment that goes on a fiberglass stick to open up a switch (of various types - bladed, fiberglass cutout, whatever) that is carrying load. On our system, if there was no upstream recloser beyond the failed recloser (so the failed device was at the substation, basically), the high side breaker at the station would have opened on overcurrent, because we'd rather it open up than burn the world down. I can only imagine that the protection scheme is different if you have critical loads (hospital, industry) that the engineers are trying to keep on at all cost. angryrobots fucked around with this message at 17:52 on Sep 2, 2014 |
|
#
¿
Sep 2, 2014 17:20
|
|
|
Another example of failed fault protection from the OSHA thread : http://www.youtube.com/watch?v=mvNA2kawKVE Couple minutes in, you see a house that is obviously getting fed primary voltage over its service. Description says a 30 kV transmission line fell onto the 13 kV distribution line, which may be but I suspect that one of those primary lines fell onto the neutral.
|
|
#
¿
Sep 4, 2014 23:27
|
|
|
Jyrraeth posted:Right now mother nature decided that September is an awesome time to dump a huge amount of snow on southern Alberta where the leaves are still on the trees. Broken branches and trees are falling on lines and I know they're fixing it. On some of our reclosers, we can view the event that tripped it out in the control panel. The fault current data can tell us about how far out the fault is. But generally in a storm we just ride to find lines down. I suppose utilities that use SCADA can probably retrieve that data as well, and get an overall map of outages and potential fault locations, maybe someone else has experience with that. Anything special, not sure what you're asking about but obviously the first step in a large outage is to get main feeders back up and on, sort of triage our work to get the most back on the quickest. Long taps through the woods will be waiting longer, that's the price of having private property way off the road. The exception is of course when company executives or the mayor or who the gently caress ever is out, and we will get pulled to get so-and-so's lights back on, because that's the way the world is. 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.
|
|
#
¿
Sep 10, 2014 19:03
|
|
|
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'.
|
|
#
¿
Sep 11, 2014 12:51
|
|
|
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.
|
|
#
¿
Sep 14, 2014 15:12
|
|
|
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.
|
|
#
¿
Sep 14, 2014 21:17
|
|
|
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?
|
|
#
¿
Sep 15, 2014 00:11
|
|
|
Will it be worth the investment?
|
|
#
¿
Jan 9, 2015 00:31
|
|
|
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
|
|
#
¿
Jan 22, 2015 18:58
|
|
|
That's pretty wild. I've seen faults on wire, where it whips around everywhere, wouldn't have expected an m3 switch to warp like that.
|
|
#
¿
Jan 31, 2015 14:35
|
|
|
A lineman was killed today in Texas, working to restore power after a storm. Unofficial reports in the lineman community say it was backfeed from an illegally connected consumer generator.quote:A lineman working to restore power in Tyler County was electrocuted. http://www.12newsnow.com/story/28933066/lineman-killed-while-working-to-restore-power-in-tyler-county
|
|
#
¿
Apr 30, 2015 02:08
|
|
|
This is what happens when copper thieves cut loose the Source Load (neutral/ground) from a set of in service voltage regulators in a distribution substation. The equipment is electrically floating and it turns concrete into glass trying to find ground.  You can see in the above picture that the max/min history hands on the step indicator dial show that this unit boosted all the way +16 and bucked almost maximum as well, hunting around trying to reach its setpoint with no neutral for the load it was carrying. All three units had the same situation, electrically, I assume this one was carrying the most load, or at least it was after the circuit lost its ability to carry the unbalanced load. The other units only glass streaks outlining where they sat. The thieves escaped unharmed somehow, but have been caught. To get a slap on the wrist or whatever, they generally get minimum punishment.
|
|
#
¿
Jun 2, 2015 00:16
|
|
|
some texas redneck posted:My question is, what happens to everything downstream when some idiot does that? Is there sufficient protection to prevent something like that from affecting utility customers beyond a brownout/blackout? Or do they get a Fortunately this is a very rural location, the calls they were getting were irrigation pivot pumps not working, cell tower called in with voltage alarm, etc. Depending on lots of variables, you may or may not have noticed it, especially the lower your load. As far as "surge protection" goes, I'm no expert on it, but I assume you'd actually need something that would disconnect you from utility power automatically, like a UPS. A word on surge protection in general, from what I've noticed there's not necessarily any rhyme or reason where lightning ends up at, and there's not much you can do about a direct or nearby strike. I've had to deal with quite a few customers who blame us, but we have a LOT of lightning arresters online, I don't know what else we can do about it. I think the best thing you can do to protect yourself is to verify the ground connection at your service. An electrician or maybe your utility can check your ground rod with an earth resistance tester. And often, it doesn't even come in on the power line, lightning can get on a phone line and run for miles. Here's one I found that was pretty... obvious.  
angryrobots fucked around with this message at 05:39 on Jun 13, 2015 |
|
#
¿
Jun 11, 2015 01:31
|
|
lesson about how important surge protection is?
|
Megger is a brand name that sells a variety of test equipment; ground resistance testing is not my area of expertise, but I know a few who do it sometimes, and they all refer to their equipment as a "megger". The test equipment I've seen used at service locations is the clamp-on type.
|
|
#
¿
Jun 11, 2015 18:06
|
|
|
I work on power lines. The god drat thing that the guy checks ground rods with, says "megger" on it and that's what they call it. I went to a troubleshooting course with the TVA one time, and the instructor from two states over, also called it a "megger". What can I say, line work is a large fishbowl and slang terms abound. But I edited it out of my post anyway, so that's that.
|
|
#
¿
Jun 13, 2015 05:52
|
|
|
some texas redneck posted:
Sometimes they don't work, or weren't installed. So you open up equipment and look for something burnt up. Find nothing, pull off a termination halfway and throw a new fuse in to find it the hard way. If it holds, keep picking up a section at a time until it blows, and you've found it. If it blows, you know it's in the first half. Split in half again and re-fuse until you isolate the bad section of wire, or whatever is bad. They make test equipment that potentially can give you exact distance to the fault, but a service man called out won't have that (big and heavy equipment) and his goal is to get the lights back on. So... Every time they threw that fuse in, looking for the fault, the recloser that feeds your circuit saw the fault and operated one time on a fast curve, blinking your lights. If you ever have your lights blink 3 or 4 times in a row, then go out, more than likely there is a fault on your circuit and a recloser operated through all its curves before locking out. quote:And by flicker I mean they went completely off, then came back to full brightness immediately, so it's not like an auto recloser was involved quote:How common is it for a poco to actually call someone back at 4am to respond to a complaint of flickering lights? That really blew my mind, especially the fact that they had someone extremely knowledgeable call me. As quiet as the background was, there's no way he was in the field. Kind of sucked being woken back up, but I was really impressed that they actually called, AND took the time to explain what was going on. angryrobots fucked around with this message at 22:22 on Jun 24, 2015 |
|
#
¿
Jun 24, 2015 22:19
|
|
|
I work for a relatively small cooperative, and that would have been repaired immediately.
|
|
#
¿
Jun 25, 2015 12:53
|
|
|
We use it a fair bit for jumpers, but in some cases I think it's just a case of "that's the way we've always done it".
|
|
#
¿
Jun 30, 2015 13:57
|
|
|
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.
|
|
#
¿
Oct 23, 2015 18:00
|
|
|
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 |
|
#
¿
Oct 23, 2015 18:41
|
|
|
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 |
|
#
¿
Oct 26, 2015 04:33
|
|
|
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 |
|
#
¿
Oct 26, 2015 21:08
|
|
|
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.
|
|
#
¿
Oct 27, 2015 20:44
|
|
|
|
| # ¿ Apr 28, 2024 09:08 |
|
|
Zemyla posted:https://www.youtube.com/watch?v=iYupPFZjuJw Building everything with transmission line clearance for one very specific and rare problem would be cost prohibitive. Although in this case, they may need to set a pole in line to shorten that span. We had this issue on a standard 3 phase line a few years ago and hung crossarms flying midspan to keep the wire separated.
|
|
#
¿
Mar 26, 2016 14:49
|
|