Yep, high power lines can be dangerous - Page 1
Forum section: electronics / general

author: woody
author_rank: Frequent Contributor
timestamp: March 10, 2018, 07:16:43 pm
content: Yesterday in Amsterdam a (power) company dug up and damaged a grid cable that was still carrying power. This lead to an overload in another cable, elsewhere in the city. That cable (or more likely a weld) exploded spectacularly as shown on this security camera footage:https://nos.nl/video/2221492Two people had to be treated in hospital for minor burns. Still, they were lucky, as was the pedestrian that passed over the already lifting paving.

author: Ampera
author_rank: Super Contributor
timestamp: March 10, 2018, 08:20:19 pm
content: Video doesn't appear to load for me, Chrome on NT 2016, everything most recent.However, water is wet.

author: IanB
author_rank: Super Contributor
timestamp: March 10, 2018, 08:28:43 pm
content: That's a pretty spectacular explosion. And I don't think it needs to be a grid cable to do that either. In that location it's more likely to be a regular buried medium voltage distribution cable.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 10, 2018, 11:58:52 pm
content: Yikes, literally hell opening up!Tim

author: Brumby
author_rank: Unknown
timestamp: March 11, 2018, 03:26:11 am
content: Quite a flame from nowhere!

author: ucanel
author_rank: Regular Contributor
timestamp: March 11, 2018, 04:26:26 am
content: Quote from: TwoOfFive on March 10, 2018, 08:20:19 pmSame issue unless without using proxy,so I found the same video on youtube:

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 12, 2018, 01:06:45 am
content: Some years ago a couple of Verizon workers, who were on strike at that time, decided to cut a trunk line but instead cut into a 13KV line. The guys died almost instantly and the woman, his girlfriend, died after being burned by plasma. So, be careful what you cut into...Brian

author: Brumby
author_rank: Unknown
timestamp: March 12, 2018, 01:16:19 am
content: I once knew a guy who worked for our local electricity supplier. Came in to work one morning to find an unusual bit of activity ... three copper thieves picked the wrong cable.

author: jordanp123
author_rank: Regular Contributor
timestamp: March 12, 2018, 02:25:42 am
content: We had a copper thief come in and steal some copper from one of our substations several years back. 69KV-12.47KV, it was a Delta-Wye connection and they cut the Wye connection neutral, along with almost every ground bond we had. This station served residential loads so a unbalanced connection was the norm. We later came to call this guy "Houdini" as we found no *ahem* lost members, and after calling around to the local hospitals no one who came in with severe burns. Only thing we found was bolt cutters that you would buy at the local hardware store with huge burn holes in the mouth.

author: Galenbo
author_rank: Super Contributor
timestamp: March 12, 2018, 11:59:16 am
content: That doesn't look at all like the 400V and 11KV electric fires I saw.There's no copper spitting, the velocity and fire distribution is different.Looks more like a mid-pressure gas fire.

author: Beamin
author_rank: Super Contributor
timestamp: March 12, 2018, 12:14:09 pm
content: Quote from: woody on March 10, 2018, 07:16:43 pmIt says I need "adventures in social media cookies" to watch the video?

author: Beamin
author_rank: Super Contributor
timestamp: March 12, 2018, 12:24:59 pm
content: Quote from: Galenbo on March 12, 2018, 11:59:16 amI thought the same thing because it was so orange. Maybe it vaporized the rubber and flashed over when it hit air. The first smoke is white like unburned vapor.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 12, 2018, 01:21:12 pm
content: Quote from: Galenbo on March 12, 2018, 11:59:16 amOil insulated cable ?

author: G7PSK
author_rank: Super Contributor
timestamp: March 12, 2018, 02:02:54 pm
content: Even a 240 volt power line can do a lot of damage. They were laying a new water pipe outside my mother in laws house to a new house next door and the contractor managed to cut the 240 volt power line with an JCB. The arc cut a big chunk out of the bucket asa well as lifting the bround all the way back to a pole 30 feet away.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 12, 2018, 02:17:36 pm
content: Quote from: G7PSK on March 12, 2018, 02:02:54 pmeven in the UK the have the Metric System.Maybe you heard about?Thats why I try to wear flame Resistant Cloth! You never know when someone do a stupid thing!

author: IanB
author_rank: Super Contributor
timestamp: March 12, 2018, 02:27:07 pm
content: Quote from: Lord of nothing on March 12, 2018, 02:17:36 pmSorry, but 30 feet is a metric. So it's definitely part of a metric system.

author: Jeroen3
author_rank: Super Contributor
timestamp: March 12, 2018, 03:07:04 pm
content: Quote from: mikeselectricstuff on March 12, 2018, 01:21:12 pmI read somewhere it was some type of sleeve that occasionally fails this spectacularly. It should have been replaced ages ago though.But I do not know if this source was reliable, since I cannot find it anymore.

author: IanB
author_rank: Super Contributor
timestamp: March 12, 2018, 04:26:22 pm
content: We have to think how many megawatts one of those distribution cables can deliver in a fault condition before the circuit is interrupted. If the fault current is hundreds (thousands?) of amps at tens of kilovolts that's a lot of energy to be dissipated. If it vaporizes the copper and the surrounding insulation that will produce a high pressure, flammable vapor cloud that has to go somewhere. At such voltages there is practically no resistance to limit the current.

author: Ampera
author_rank: Super Contributor
timestamp: March 12, 2018, 05:09:30 pm
content: Quote from: IanB on March 12, 2018, 02:27:07 pmI'm sorry Europangeans, it's 10 yards, and yards are identical in every way shape and form (except for where they're not) to meters, or metres, or meaters.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 12, 2018, 05:20:14 pm
content: Quote from: TwoOfFive on March 12, 2018, 05:09:30 pmI prefer meateaters.Tim

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 12, 2018, 05:21:57 pm
content: Quote from: TwoOfFive on March 12, 2018, 05:09:30 pmWikipedia say: 1 yard = 3 feet = 36 inches = 0,9144 Meter

author: The Soulman
author_rank: Super Contributor
timestamp: March 12, 2018, 05:26:49 pm
content: Quote from: TwoOfFive on March 12, 2018, 05:09:30 pmNope, one yard equals three feet equals 91,44 centimeters, the hard part is to actually convert that to meters by dividing by 100.So 91,44/100=0,9144 meters.I understand this metric stuff is way to advanced for people on the other side of the lake.

author: IanB
author_rank: Super Contributor
timestamp: March 12, 2018, 05:28:24 pm
content: Quote from: Lord of nothing on March 12, 2018, 05:21:57 pmWell, there you are then. You are comparing a nice round number of "1" with a complicated decimal of "0.9144". It's obvious which one is neater and more convenient to work with

author: Ampera
author_rank: Super Contributor
timestamp: March 12, 2018, 05:31:14 pm
content: What you guys forget is I'm smart enough to operate in both systems, while all y'all are too stupid to use our intricate and complicated units.Love from the US!

author: Marco
author_rank: Super Contributor
timestamp: March 12, 2018, 06:09:57 pm
content: Quote from: TwoOfFive on March 12, 2018, 05:31:14 pmYou're only human ... genius level IQ people have screwed up due to imperial/metric/nautical/statute conversions.Wish post WW2 US military dominance hadn't screwed us over with your nautical miles and knot bullshit.

author: Ampera
author_rank: Super Contributor
timestamp: March 12, 2018, 06:36:48 pm
content: Quote from: Marco on March 12, 2018, 06:09:57 pmYou could have at least given us the good pyrex, not let some idiots make this blue tinted tempered glass stupidity.Units are units. Truth be told, the US doesn't use our customary units too much anymore. Our roads, cakes, and cars are measured in US customary, with the most technical application being construction. Pretty much everything else is SI.

author: Vtile
author_rank: Super Contributor
timestamp: March 12, 2018, 07:14:42 pm
content: Quote from: The Soulman on March 12, 2018, 05:26:49 pmsince when? Meter is the base unit and the US customary units are now defined from SI base units. So the correct is:yard (yd) .............................................................. meter (m) .................................................... 9.144 E?01Source: Guide for theUse of the InternationalSystem of Units (SI)NISThttps://physics.nist.gov/cuu/pdf/sp811.pdf

author: Galenbo
author_rank: Super Contributor
timestamp: March 13, 2018, 03:50:03 pm
content: Quote from: mikeselectricstuff on March 12, 2018, 01:21:12 pmNever heard of that, never saw that, thanks for the remark, I'll look it up.Here in Belgium power lines and gas often are close to eatchother, it can still be a short-circuit that induced a gas fire.In the netherlands they speculate about an earth/fase short.https://www.circuitsonline.net/forum/view/140314

author: Iwanushka
author_rank: Frequent Contributor
timestamp: March 13, 2018, 06:53:36 pm
content: Quote from: Galenbo on March 13, 2018, 03:50:03 pmGood old cables had paper, oil and lead "shielding"

author: jmelson
author_rank: Super Contributor
timestamp: March 13, 2018, 09:02:38 pm
content: Quote from: TwoOfFive on March 12, 2018, 06:36:48 pmHUH? CARS? Everything on our cars has been metric for 30 years, EXCEPT the wheel lug nuts and the oil drain plug. (And, I think a bunch of makers are coming over on those items, too.)Jon

author: Brumby
author_rank: Unknown
timestamp: March 13, 2018, 10:21:07 pm
content: While off-topic, following on from the units discussion ... the ones that get me have nothing to do with the metric system. It's the US/imperial gallon and ton.At least with the metric system, there is only one definition of anything.

author: Ampera
author_rank: Super Contributor
timestamp: March 13, 2018, 10:37:43 pm
content: Quote from: jmelson on March 13, 2018, 09:02:38 pmI mean the use of cars, not the construction. Probably should have said gas pumps instead, but roads, speeds, and almost anything outside of servicing is customary. Makes sense, though, since the automotive industry is a heavily internationalized one.

author: Beamin
author_rank: Super Contributor
timestamp: March 14, 2018, 11:47:09 am
content: Quote from: The Soulman on March 12, 2018, 05:26:49 pmHave you not seen American TV documentaries? Everything is measured in football. The wire was 1/10 of a football field long. The circumference of the earth is 300000 football field around. The speed of light in an inflated football is 78236817624 football fields per second. Your wifi runs at 2.4 pico half times per second.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 14, 2018, 11:57:58 am
content: the same here in Austria the say often the Size is X from an Soccer Field.

author: Gromitt
author_rank: Regular Contributor
timestamp: March 14, 2018, 01:02:42 pm
content: Quote from: Lord of nothing on March 14, 2018, 11:57:58 amI think you mean 'real football field'

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 14, 2018, 01:30:35 pm
content: sure. I just hate the "sport".

author: Ampera
author_rank: Super Contributor
timestamp: March 14, 2018, 02:09:18 pm
content: I've never seen a game of US football, also known as rugby for wimps.I've never seen a game of rugby either.I don't usually watch sports, but I do like a good baseball or soccer match, especially if it's live. I watched the 2016 Cubs world series game 7, and that was a game to never forget. It's almost as if the planet itself was doing all it could to make the situation more epic.

author: Zucca
author_rank: Unknown
timestamp: March 14, 2018, 02:10:52 pm
content: Why not the fuse but the buried cable?As I understood you invest money in a fuse to save the expensive cable and the effort do dig it up in case something goes wrong, in this case that line had no protection.Am I wrong?

author: IanB
author_rank: Super Contributor
timestamp: March 14, 2018, 03:10:12 pm
content: Quote from: zucca on March 14, 2018, 02:10:52 pmMost likely the cable had some protective devices. However, it must be remembered that such a cable is designed to deliver large amounts of power from point A to point B. The cable is therefore also able to deliver large amounts of power into a fault. The protective devices cannot necessarily tell the difference between a normal load and a fault situation.

author: Zucca
author_rank: Unknown
timestamp: March 14, 2018, 03:14:13 pm
content: Quote from: IanB on March 14, 2018, 03:10:12 pmwell in my eyes that protective device is not well designed and it is not doing his job.

author: jmelson
author_rank: Super Contributor
timestamp: March 14, 2018, 03:45:23 pm
content: Quote from: zucca on March 14, 2018, 03:14:13 pmLow voltage systems (up to 480 V or so) will tend to weld to a dead short, and blow the fuse promptly. High voltage systems (and really, here, the power systems pros will call this medium voltage, 4000 - 14000 V) tend to arc and not weld to a dead short. We had a feeder at work right out of the transformer short out. All the lights on campus went out, and there was this huge arc burning underground toward the transformer. They had to wait for a guy from the electric utility to come out in a truck to turn off the HV into the transformer. Then, they just cut off the wires to the failed feeder with a hacksaw and turned it back on. We had 4 parallel feeders that were connected together at each end (transformer and switchgear). Due to induced currents in the conduit, they have to run all 3 phases plus neutral in each conduit, so the induced current nulls out.Jon

author: SeanB
author_rank: Super Contributor
timestamp: March 14, 2018, 05:36:58 pm
content: Well, the blast is typical of an old paper insulated cable failing, probably due to water ingress from a corroded lead sheath on a joint, or the cast iron sheath corroded a pinhole. They can and do excavate themselves in the half second or so it takes for the MV circuit breaker to trip out, as those are designed to have a slight delay so they do not trip out when you power on a cold load after either a power failure or after it has tripped out due to a fault. Cable and switchgear is designed to survive the heating longer than it takes to trip out again, to isolate the fault, not to limit arc damage.I have seen them dig a hole in the road 6m deep, as that is how deep the join was when the 33kV line failed early one morning. road was closed, seeing as there was no more lane either way, and the pavements were somewhat damaged as well by the blast.Funny thing is 11kV cabling is a lot faster on protection, the guy with the pickaxe from Digotel (the colloquial name for the fibre layers, who are capable of finding every water pipe, cable and phone line in the road it seems) just had a wake up call, and a 1cm bite in the tip of the pick axe he put through the joint.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 14, 2018, 07:30:44 pm
content: Quote from: zucca on March 14, 2018, 03:14:13 pmSo how do you tell the difference between, say, a resistive load drawing 50kW and a resistive fault ( due to carbonised burnt stuff) drawing 50kW?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 14, 2018, 07:38:37 pm
content: Quote from: mikeselectricstuff on March 14, 2018, 07:30:44 pmThere are arc fault detectors, which monitor for the high frequency, noisy content generated by the latter. I don't know how widespread their deployment is, though.Tim

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 14, 2018, 10:31:12 pm
content: Quote from: T3sl4co1l on March 14, 2018, 07:38:37 pmHigh voltage arcs are detectable fairly easily due to the HF content from the sparks, but I'd expect that at lower voltages a "cable on fire" type fault looks more like a resistive load, as the resistive path means you're not going to get much sparking after the initial failure.

author: Zucca
author_rank: Unknown
timestamp: March 15, 2018, 01:06:40 pm
content: Quote from: mikeselectricstuff on March 14, 2018, 07:30:44 pmYou can't, the same will happen in an apartment if the failure will drawn 14,9A with a 15A protection thing.

author: Beamin
author_rank: Super Contributor
timestamp: March 17, 2018, 08:49:11 pm
content: Quote from: zucca on March 14, 2018, 02:10:52 pmThere is a lot more to it then that. But say that was the solution; a lot of privately owned companies would rather gamble taking the risk; pay for damage and law suits then pay for upfront costs. A corporation only exists 3 months at a time. Quarter to quarter. For example many companies know that raising the minimum wage would in the mid to long term equal higher profits: they have mathematicians and actuaries that are paid a lot of money to figure this out they are way too smart not to know this. But that would mean a 100% chance of losing profits this quarter for a 90% chance of more profit in 6 months to a year. No company wants to front the cost because of the way a corporation is obligated to its shareholders that can leave in seconds due to the stock market. Crazy.Also I realized if something has an obvious answer but no one is doing it most of the time it's because I don't know all the details.