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Comment by taneq | Hacker News Reader

> Backfeeding the power grid, according to some lineworkers I've talked to, is really not a big concern for two reasons. First, lineworkers assume lines are live until proven otherwise. And, second, no residential system is going to successfully backfeed a large dead section of grid. [...] it's really not that big a concern from a technical/safety perspective.

This is wrong and dangerous. Suddenly energising a section of grid which has been isolated from all known power sources could easily kill someone working on it. Yes, lineworkers will isolate and test lines before touching them. No, this won't protect them because your inverter could start outputting after they've tested. Yes, your inverter will probably overload and trip out before putting too much voltage into your local section of the grid, depending on where it's isolated. No, it's not OK to bet a random stranger's life on it.

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I like to always highlight the difference between a technically correct statement and a public health and safety policy statement.

A thing may be technically correct, but for the health and safety of the public at large we need to adhere to a consistent policy with what we say in the public sphere.

Mains voltage is dangerous and kills kills kills. Never connect anything to the mains power supply unless you are licensed to do so, or employ someone who is licensed to do so. Always assume a circuit is live unless you-personally have checked and locked out the breaker with your own personal lockout device that only you have the key to.

You are supposed to have a license to plug a TV into the wall?

I'm being silly, but you are going on about how the wording of statements matters.

Funny enough, if you've ever done a tradeshow at a venue that has union labor, they will literally make you fill out a request and wait for a licensed union electrician to come and plug your TV (or phone charger or anything with a plug). You will then receive a bill for their time.

And if you plugged in your TV yourself, and they find out, you just unplug it immediately and wait for the licensed union electrician to come plug it in for you again.

I hope you are not suggesting that that is in any way reasonable.

In my country, it's required by law for every employee to have a certificate even for plugging in a toaster. The training is easy though and serves mostly to prevent injuries.

What do they teach you not to do?

Question ever-expanding bureaucracy?

What does the training cover?

"Do not rest your tongue on the plug as you insert it into the wall."

I get that electricity is dangerous, but are there really functioning adults hired by a company that can't be trusted to plug in a simple appliance without a safety briefing first? It seems insulting to their intelligence. Or do they make everybody do this so the one or two absolute morons don't feel bad about being forced to take the "completely basic life skills" course before they're allowed to function at even a very low adult level?

That's not been my experience (in a previous life I did 5-6 shows a year, and was yelled at by union reps more than once for hand-carrying my own materials in). At the shows I did (which included venues like the Cobo Center, various downtown hotels, and other union-heavy shops), the union electrician would wire up an outlet for you, but you were then free to plug in what you wanted (as long as it was UL-listed).

I worked in a public university office for a while in college. Without involving the unions, we couldn't

- move furniture that didn't have wheels (so no moving of desks, side-tables, or even some of the larger waiting-room-style chairs). We were allowed to install wheels on furniture ourselves and then move it however :)

- hang pictures or anything on the wall (except when using that blue tacky stuff; you'd be surprised what you can hang with massive quantities of tacky)

- plug in a new power-strip, surge-protector, or extension-cord (we quickly learned to get the big 20-outlet strips)

- set up any kind of networking equipment, even if it was air-gapped from the university's network (we violated this all the time)

- plug in anything that drew more than a certain number of amps (an amperage level that was quite close to what many tower desktop computers were drawing at the time; we always just risked that)

Union workers were always prompt and polite when we'd ask them to do these things and they always had a "ya we know it's dumb" attitude about these requests. One time I saw the bill for the services: around $50 to plug in a surge-protector (that we provided) and $100 to nail a framed picture into the wall. The fine for not getting the union to do these jobs was something like 10x the cost of the labor iirc.

I'm curious how some unions devolve into this sort of behavior. The incentive is obvious, but I wonder if there's an organizational solution that would counter these outcomes.

On the bright side, at least you know your electricians weren't being exploited :)

I'd wager that somewhere in their organizational past is a burned down building and an appliance connected to the mains with a wire hanger, at which point they decided that nothing is so fool-proof that a sufficient fool cannot be found.

> I'm curious how some unions devolve into this sort of behavior.

Well, actually there's a logical reason why only the union workers were allowed to do the mentioned things (tl;dr: company/university wants to shield themselves from liability):

- move furniture: shield the university from injury claims in case something goes wrong. For example, consider you moving a yuge chair around wearing flip-flops and you accidentally crush your toe during lifting. The university can now deny your claim as you were not supposed to have done this. In the crazy US system with its even crazier damage payouts, I wonder why this isn't commonplace.

- hang stuff on walls: the older the building, the bigger the chance that you'll hit some live wire, a water pipe or whatever is buried in the wall. Plus, again, personal injury claim risk.

- set up networking equipment: all it takes to bring the network to a grinding halt is accidentally connecting that router you planned to use for playing Counterstrike to the university network and whoops, where's that extra DHCP daemon coming from?

- amperage limit for devices: older circuit breakers tend to get a bit... trigger happy with age. Which means what will work fine now may be too much (especially surge) load in a couple of years and these issues are tricky to debug. In addition, I have seen a wild variation of power cables and extension cords when it comes to their current capacity (e.g. there exist power cords with 3x 0.75mm2 wire, these are rated for 2.5A tops aka something around 550W - but what if the component uses 800W?). Having someone trained look at all involved components before plugging them in can and will prevent fires. Not only to check if they're safe from an amperage limit, but also to check if their isolation is broken, there are scarred areas from arcing, ...

Those make sense... except the hanging stuff on walls is a stretch. You'd have to use a 6" nail to manage to hit a wire or pipe behind the wall. Most likely, they just don't want lots of little holes in the walls.

A person without knowledge of what is inside of a wall or why it could be a problem may indeed try to use a 6" nail to hang their picture.

There are plenty of people that don't understand(and probably don't want to understand) how things are connected. I doubt they think that the light switch magically turns on the light, or that the water magically comes from the valve attached to the wall, but the method, or desire to know the method, in which those things happen is just not in their world.

> You'd have to use a 6" nail to manage to hit a wire or pipe behind the wall

Nope. There's a type of wire called "Stegleitung", essentially a flat cable. Often enough it's simply nailed into the wall, then a thin coat of mortar is applied on the wall, and then paint.

Source: zapped myself once by hitting such a cable.

In addition, the usual injury liability is a problem.

Ya it's all exactly this. The rationale for all these things seemed somewhat sane, but in practice they ended up being irrational when applied in the extreme. It's totally CYA stuff that's typical in public/government settings.

RE the wall they also said that nails and tape were also damaging to the paint (and repainting the walls was another union's thing), so the wall-hanging guy would have to log the "damage" to the wall caused by the hung item, presumably for cost/accounting purposes when it came time to repaint the wall.

> It's totally CYA stuff that's typical in public/government settings.

That CYA stuff is actually typical for any company that ever gets hit with a personal injury or other expensive lawsuit. It's pervasive in government/bigco's because they had to deal with decades of every imaginable stuff happening.

If you want to get rid of it, you gotta limit personal injury liability (which would border on being inhumane) or develop a decent social safety net with proper insurances...

> It's pervasive in government/bigco's because they had to deal with decades of every imaginable stuff happening.

This is important: big orgs—government and private—not only have more chance of having an incident (because they deal with more events because of their scale), they are often bigger litigation targets when an event occurs, because they are giant bags of money.

> I'm curious how some unions devolve into this sort of behavior.

Distrust—usually well earned—of management is the main way. The incidental items that are mocked are not the issue, the issue is that without an inflexible blanket rule, management will bend any other rule to use people in nominally different job duties to replace union labor.

Also, sometimes, the rules are negotiated in part by unions other than those doing the work, to prevent their covered staff from being compelled to do other kinds of work (and selected against for inability to do so: if lifting heavy items is part of the job duties of, say, someone in a clerical union, then inability to do that well can be used as a hiring, promotional, or termination consideration for such an employee.)

Even in places (as sometimes happens) where orgabized labor and management have good day-to-day relations, there usually is a feeling—with good historical reasons behind it—that the foundation of that good relationship is a “good fences make good neighbors” style solid set of baseline rules around which, where it is important (and the little stuff that is fun to mock isn't that) negotiated exceptions can be made.

Ha! Good one ;)

Yes, it’s meant to say something like us unlicensed folk aren’t permitted to hardwire anything to the mains supply.

In Australia you’re not even supposed to replace an existing power point outlet thingo unlicensed. If course, the hardware stores sell them, and we do. But there ya go.

> In Australia you’re not even supposed to replace an existing power point outlet thingo unlicensed.

In fact you're not allowed to install any fixed wiring without an electrical license. It's ridiculous - technically you aren't even allowed to install Ethernet outlets in your own house because it counts as "fixed wiring". Other trades have just as bad a grip on legislature, you're technically not allowed to replace your own tap seals either.

> Of course, the hardware stores sell them, and we do. But there ya go.

Of course, in theory there's no difference between theory and practice... ;)

As far as I know... there's no documentation of home power systems in the US.

So the difference between "electrician installed" and "mysterious, unknown person installed" is only in the finished product.

Indeed. It happens all the time that a homeowner does significant wiring projects in their own home. Everything you need is available at the local hardware store or Home Depot. Some do a good job. I've also seen things like lamp cord used in fixed wiring behind walls or in attics.

I inherited some piece of furniture - I don't recall what - that my wife's ex had attached a florescent lamp to. He used a telephone cord for the 120v power connection.

People who can't explain how current, voltage, and resistance relate to each other shouldn't be allowed near wiring.

A fluorescent lamp that one would attach to furniture probably only takes 10W. That's less than 100mA at 120V; a telephone wire can handle that. Also, telephone wires once carried as much as 50VDC for ringers, so I'd expect the insulation to be adequate, if only barely. The biggest problem, I think, is that because the insulation is relatively thin, there's a greater risk of mechanical damage to it.

One slightly obscure example is someone using a European (220V) light fixture or extension cord (with plug adapters) in North America. (110V).

The current for the same wattage will be roughly double in North America. So lamps, etc. intended for use in Europe will have wiring that is undersized for the current draw if used in North America.

> I've also seen things like lamp cord used in fixed wiring behind walls or in attics.

We found exactly that, lamp cords and extension cords, when we started our remodel a month ago. The former owner did some renovation ten years ago, and was an architect so we always assumed he did a decent job. That was one of a few questionable choices he made, so we're now re-wiring the entire house.

An old house that is rewired would have a permit on file if it were done properly, and includes the name of the contractor if there is one. But there is often no proof on site.

Electrical work can be done properly without a permit having been pulled. Depends on where I suppose but even contractors often don’t get permits.

In Australia all work carried out by an electrician is required to be certified. That is to say, the electrician must, on completion of the work, hand you a certificate stating that all work is to the relevant standard. They can't reasonably withhold the certificate, and it must be provided on completion not on payment.

An organisation called TechSafe[1] is charged with carrying out random inspections.

1. https://www.techsafe.com.au/

I include pulling a permit as part of doing a job properly.

I had house that had a high quality ceiling fan that always made noise. It was high and hard to reach but after perilous ladder work I discovered it wasn't the fan; it had been wired up wrong, the variable speed control was wired up across the two separate 120v legs supplying the home with electricity. I was surprised that the fan even worked at all that way. I don't know who wired it up originally.

I'm not an electrician so correct me if I'm wrong, but for those unfamiliar with residential wiring in US homes, ordinarily homes are supplied with two out of phase 110VAC lines. Heavy appliances like electric clothes driers and electric car charging points use the 220VAC that I available between the two "hot" lines. Everything else in the house use either one of the "hot" lines (black wires according to the national electrical code). There are actually 3 wires going to each outlet, light, etc. though the house: one black (belonging to one of the two sources of 110VAC), one white (called the neutral line, approximately 0V above ground, and one green a separate green wire that is connected to ground around the point where power enters the house.

Correct, but they're 120/240V. Or at least, should be.

It's actually 120V/~208V. If you're feeling frisky, you can confirm this by going around between random pairs of outlets in your house and comparing the right slots from two different outlets until you find a pair of them that are out of phase from each other.

Fundamentally, the power grid is based on three phase power. Typically, the average telephone pole will have four power wires on it, and one or two thick bundles of phone line or maybe cable TV, I dunno. Three of those four power lines are the three phase electricity, and the fourth is the common neutral line that is ideally near 0V, but typically fluctuates a bit.

Only three out of those four lines enter your house. One is is the neutral line, the other two are just two of the three power lines. Those two power lines are not 180 degrees out of phase, they are 120 degrees out of phase. If they were 180 degrees out of phase, the math is simple: it's obviously just 240V. Since it's 120 degrees out of phase, you end up with a sine wave that looks something like 120\(sin(x)-sin(x+pi\2/3)). (only you need to adjust it for frequency) If you're better at your trig identities than I am, you can calculate that out exactly, but for simpletons like me I just plug it into my calculator and find a local maximum of 207.846 something.

(note: In the US, we use neutral and ground to refer to the common center of the three phase power, and the wire that is buried in the ground near your house, respectively. In the UK, I think they call these two wires ground and earth, respectively. Note that the term "ground" has a very different meaning (read: one of them can kill you, the other one keeps you safe) depending on the context.)

That's interesting, and I don't doubt that you have seen a system like that, but it sounds more like what could be expected in an industrial setting with 3-phase power.

The few houses that I was involved in wiring of in the states were definitely "split phase" systems, which work like the GP describes. In those, three current-carrying wires come from the transformer - two ends and a centre tap from one winding. Those are wired in the breaker box so that the house has two circuits that are 180* off from each other, giving 110V on either circuit, or 220V between the two "hot" legs. There's a better description at https://en.wikipedia.org/wiki/Split-phase_electric_power.

This is not correct for the majority of US households.

Two of the phases DO NOT run to the house, a typical US household service is split-phase. The primary winding in the transformer at the pole connects between a single phase and ground, and the secondary winding is center-tapped to provide a 'neutral', with 120v on either side of the neutral. The voltages are indeed 180 degrees out of phase.

Your test would show 220-240v in the vast majority of US-based residential situations.

The 120/208 you are referring to is when all 3 phases are fed in to a WYE transformer that has 3 120v secodary windings fed from a center point, which becomes the neutral. With a WYE transformer, each phase gets 120v to ground/neutral, and the phase-to-phase voltage indeed peaks at 208v due to the 120 degree rotation between phases. This is typically only found in large residential(600+ amps), and medium to large commercial and industrial buildings with 3-phase service.

Another method would be using a 'Delta' transformer, in which one of the phase-to-phase windings are center-tapped, similar but a little different than the single-phase residential service. The two phases on either side of that center-tap will be 120v to neutral, but the 3rd phase will be 208v to netural/ground. This is usually called the 'wild' leg and is often used to power lighting loads.

Source: I've been doing this for a long time.

Also https://www.doityourself.com/forum/electrical-ac-dc/549775-l...

And https://ctlsys.com/support/electrical_service_types_and_volt...

Australian protectionism re: the building industry if disgraceful.

In Victoria for example, you're not allowed to do any work on your own home if it exceeds a certain monetary value without first running through a Kafkaesque bureaucratic process to obtain a certificate.

This doesn't sound unreasonable until you realize that they don't care if you have any qualifications related to the work and don't even want to know what the work is. They simply want to confirm that you haven't done any other work (on your own property) in the last five years.

If you have, sorry, need to hire a registered builder. This prevents anyone from legally buying a home, renovating, and selling it, or even doing any significant work on your own property more than once in five years.

And if you want any other tradesperson to come to assist for anything while your doing it (installing a power point for example), then you need in person occupational health and safety training at a "registered training institute".

http://www.vba.vic.gov.au/consumers/owner-builders

Wow that is some extreme bureaucracy. So flipping houses is not a viable business in Australia, I presume.

It is, but you can't do the work yourself.

That sounds like a great way to end up buying a house with a bunch of un-licensed, un-inspected work done because the previous owner didn't want to deal with the beurocratic madhouse.

That's some serious FUD you've got going on, and a total misrepresentation of what the rules actually say.

You only need to apply to be an owner-builder if you are doing your own work instead of hiring someone who is already permitted to do the work. This is no different from the US practice of having licensed contractors/electricians carrying out (or signing off on) large projects.

That's some serious FUD you've got going on, and a total misrepresentation of what the rules actually say.

You only need to apply to be an owner-builder if you are doing your own work instead of hiring someone who is already permitted to do the work.

That is precisely what we are discussing. The restrictions on doing work on your own house yourself.

And this applies to any work at at, not just work that requires licensing (plumbing, electrical etc.). Even if you're doing the overall work yourself as an owner builder, you still need to hire licensed professionals for those tasks.

A while back there was a safety ditty from some Australian public transit organization as I recall. Things like not touching third rail and various household dangers. Perfectly sensible stuff. But there was also a line about “doing your own electrical work” which, as an American, struck me as so out of place as to be almost comical.

My brother-in-law is an electrician, and he could tell you stories for days about the horrible and unsafe practices he sees nearly every day of the week in people's homes where they've done their own work.

Everything thinks they're smart, they can do things safely, etc., while only for a much smaller subset of people is that true.

I work with industrial electrical systems so I see a lot of how things are done "the right way". The amount of horrible bullshit that I've seen in houses that's been done by licensed electricians is staggering. I'd wager for every one dodgy install done by a DIYer, there's an entire house that's been wired in the laziest spaghetti style by a 17-year-old sparky's apprentice and ticked off without even eyeballing it by the main contractor.

A fun way to trigger a dumb argument is to say something about taping (or not) wire nuts.

I mean, in the US you should be careful atleast since the US plugs expose mains voltage where your fingers might be able to reach (UK and EU plugs are much better and make it mechanically impossible to touch the exposed copper before they make contact with mains).

Generally, playing with voltages above 50V is something that should be done with care and a professional/adult present.

TR plugs are required now in the US. We replaced ours because it looks a lot better than outlet covers.

TR plugs don't prevent the spades from being exposed when plugging in a cord. They simply prevent a someone from inserting something into one of the slots like a bobby pin.

It's still a massive improvement.

But you can't safely guide the plug into the wall socket without looking at it. With European plugs[1], that's fine. The grounded version doesn't have that protection, but the female side has walls on the side and a protruding ground plug, so it's also safe to guide with your fingers: by the time the plug is sufficiently in to become live with power, the gap is smaller than the width of a toddler's finger.

[1] https://ae01.alicdn.com/kf/HTB1Cya9KVXXXXXoXpXXq6xXFXXXK/202...

Yes, I understand, but I'm not sure how you address that without changing literally every existing plug and outlet in the USA.

You could probably require the plug leads to have rubber coating on 80% of the plug material, and recess the actual contact points slightly farther back into the receptacle, which would emulate the British plug somewhat, but good luck getting anything like that past the lobbying of groups who often cut a tiny hole in one or both blades just to save fractions of a penny per plug

Those holes mate with a spring mechanism in some outlets to keep the plug attached to the outlet more securely.

That's exactly what happened in Europe. The old ones were as dangerous as the ones currently in use in the US. They managed to make the transition in a way that was backward compatible.

Here in the US we did change our plugs, by introducing polarized plugs. We don't have to be change-averse.

Sure, and the grounding pin was also added. To get around that, every hardware and department store sells those little defeat devices (that you're supposed to ground but I'd be surprised if anyone ever did that). That's an instance where the reaction to a change leaves you less safe, not more.

https://en.wikipedia.org/wiki/Cheater_plug

Good ones are also liquid proof.

Interesting, is there some image of the TR plug, I couldn't find anything online?

Found this: https://www.esfi.org/resource/what-is-a-tamper-resistant-rec...

Search "Tamper-resistant electrical receptacles". They don't really look all that different, there's just a mechanism in the holes that prevents some foreign objects from being inserted.

Yeah that's not really better at all. You can get the same protection with 3$ child-protection covers here.

The issue is exposed live voltage when you plug it in. Schuko and Europlugs generally don't allow this (even the flat plug is designed such that the contact aren't exposed anymore when they make contact)

Tamper resistant outlets are required (maybe) for new construction, but there's a lot of existing housing -- some of which has two prong, unpolorized outlets.

Hardware store still carry traditional outlets as well.

"TR" plugs are another "innovation" that someone got a patent on and then lobbied to get into the NEC. In my experience, their only functionality is to bend up the prongs on plugs when the plastic bits choose to not get out of the way.

Why should everybody have to pay a continuing overhead simply so people with small children don't have to install outlet covers?

If you're actually concerned with electrical safety, you're much better off installing solid "commercial-grade" receptacles than pretending that garbage-grade ("residential") has been rendered safe by being more difficult to use.

Do you also have an RCD[1] in the mains switchboard? Each circuit breaker in my shiny new upgraded mains switchboard is also an RCD.

I still occasionally see an old switchboard with ceramic wire fuses with the fuse wire replaced with a bit of coat hanger wire, or the correct fuse wire wrapped around the terminals ten times. They often seem to be the same houses that give you a tingle if you touch any of the metal plumbing fixtures. Yikes.

1. https://en.wikipedia.org/wiki/Residual-current_device

"Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize."

https://news.ycombinator.com/newsguidelines.html

My comment is snarky, but it doesn't criticize a weaker interpretation of what they said, it points out a problem with the phrasing. The "I'm being silly" is an acknowledgement that the snark isn't really addressing the substance, the strongest plausible interpretation of "I'm being silly" is that I understood their meaning well enough.

Fair enough on the "I'm being silly"—that does take the edge out of the comment and that's good. But I'm not sure it gets rid of it.

Pointing out "problems with the phrasing" doesn't make for very substantive discussions. Also, snark is deprecated here. Please see https://news.ycombinator.com/newsguidelines.html.

I disagree with you on the phrasing aspect for this specific case. When discussing an advertising message the phrasing is extremely important.

Albeit the thread didn't invite substantive discussion on it because of the snark.

I'm not a lineman but am a generally curious person, which has caused me to watch and analyze their work when I see it.

Any time I see them working directly on high-voltage lines, they connect a device that looks like jumper cables in-between the phase(s) and ground. They also put bright orange flags on this device so that it is easily visible to anyone nearby. It seems to be a great practice and seems to make things nearly fool-proof because this effectively shorts out any power that may occur on those lines.

I don't think I've ever seen a lineman work on a power line in a manner that would cause him to be electrocuted if surprise power were to occur on the line. I'd bet it's in policies and procedures somewhere, possibly even in OSHA requirements.

The requirement of not backfeeding is another layer in this multi-layer protection scheme.

If a system is successfully backfeeding the grid, something is badly wrong. If a linemen is then electrocuted by this backfeed, something is almost impossibly wrong.

I agree with your comment about back feeding and shorting lines that are supposed to be de-energized, but linemen also sometimes have to work on hot lines. They have all kinds of neat tools and techniques for doing this. Seeing a lineman with a cheater stick (fiberglass pole) or insulated gloves working on a live line is pretty neat.

During a flood I once saw a HV line that was occasionally dipping into the river. It would float down for a little bit, build up some tension, then shoot into the air creating a ~4-5 foot blue arc as the line shorted into the river before landing back in the water and producing a huge thumping sound.

That completely changed my perspective on all those quite lines dancing in the wind.

Yep, and when they work on hot lines, they treat them as such, using the protective gear you mentioned.

I cannot think of a time that I saw a lineman working on a power line that was not shorted, without protective gear.

Working on a hot wire is a whole different story because every thing around you becomes a hazard.

I do work on towers, sometimes in hot-RF environments (TV and radio antennas transmit with up to ~100,000 watts). The antennas will literally cook(like a microwave oven does) you if you get too close while they are live. For lower power situations, you can even hold your hand near the antenna -- it feels like a heat-lamp. Even at reduced levels, it can be harmful to areas of your body with poor circulation and cooling(such as your eyes), often causing damage before you're even aware of it. We wear an RF monitor when in those situations that alerts us if the RF field becomes stronger than is safe. I wonder if linemen wear a similar device that can alert them if an EM field becomes stronger than expected?

It's not as foolproof as it may seem. If linemen are out working it's because something has changed the normal flow of power. If they're fixing downed power lines then all bets are off as to what the circuit diagram has effectively become. They might ground out the spur going to the break but that still leaves everything after the break ungrounded. Take for example, Joe homeowner bought a big 5kW generator and he wants to keep his fridge running. It's easy enough for someone to "install" a generator themselves without calling an electrician and just make a suicide cord to hook it up during a power outage. If the break is just upstream of the generator, or the neutral broke instead of the live line, you can have a situation where the generator is still producing a lethal voltage potential between the live line and ground yet it wouldn't be low enough resistance to short out the generator.

It's unreasonable to assume that a lineman can identify which sections of a downed line are isolated before they get to work repairing the power lines. There are circumstances where the line might even be isolated without being physically disconnected because a fuse blew downstream of where the line was grounded before the lines actually came down. Fuses will have a visual indication that they are blown but it's just a pin that sticks out the bottom and it's easy to miss when you think the only problem is a downed power line. There's an army of fools who know just enough to be dangerous and it's easy to see this on YouTube. Here's a great example of what linemen have to worry about when repairing downed lines.

https://www.youtube.com/watch?v=KiByz1E4IBU

Wouldn't you be worried working with downed lines not knowing if that guy just so happened to live across the street?

I think I would take the same advice as is given for someone handling a gun -- treat every gun as if it is loaded. Treat every wire as if it is hot. Unless you have a really good reason not to.

Not doing so is putting an awful lot of trust into a potentially large number of people that you've never even met.

Because you just don't know what some idiot has done...like the guy in the video.

When I work on electrical wires at home, I test if they are hot after flipping what I believe is the correct fuse. If I’m right I know it won’t become hot while I work on it because I control the switches and fuses.

If I worked on wires where I was not in control of incoming power, then I can not be sure the wire isn’t hot just because I measured once. This is for example the case when working with stuff with big capacitors.

So my point is: can line workers really assume a wire isn’t hot just because they tested it? They don’t control both ends, since as you pointed out, anyone could have a) a power source or b) a faulty connection, whether it’s allowed or not. So as a line worker I’d basically just not touch anything even in supposedly dead grid sections.

When they work on train power lines, what they do is physically short them to the tracks.

I recommend shorting to ground. Even if it's your own fuse. Shorting means that if you picked the wrong fuse you notice. And when your friend comes by and flips the fuse back on you don't get a spark shower (something like this has happened to me, don't underestimate people willing to flip fuses for no reason)

A common solution for this is lockout-tagout, where you physically lock the breaker open using a lock with your name on it, and nobody can flip it until you come back and take the lock off.

Used on electrical circuits as well as dangerous machines if you need to climb inside a compactor for maintenance or something.

https://www.osha.gov/Publications/3120.html

http://www.deenergize.com/?target=Universal_Circuit_Breaker_...

That works too, though IIRC the common procedure in the industry in my country is to use a warning label/shield and hang it on the breaker box during repairs, locking the breaker box itself, then short out the circuit to ground and measure to be sure.

Locks on the breaker itself are more rare (usually for low voltage repairs where the common person might frequent the area)

You should test if they are hot before you flip the breaker, then test again after. If you only test after you are not protected against faulty test equipment or improper wiring.

Yes. This was assuming the light was shining (or equiv, that it showed 230V) before work starts of course.

I'm so paranoid I lockout-tagout my home breaker panel.

> Yes, lineworkers will isolate and test lines before touching them. No, this won't protect them because your inverter could start outputting after they've tested.

The lineworkers I've seen that aren't working with live wires use a special tool to ground the wires (it's a set of three clamps connected by a thick wire to a grounding rod). Once the wire's grounded, it's going to be hard to put any voltage on it.

Here's a photo just after they did that while repairing a break near my house a few months ago: https://i.imgur.com/6TckAa8.jpg

The obviously missing third top line is the one that broke. It simply snapped around the middle of the span between that pole and the pole that is outside the photo on the right. They went up in the cherry picker, cut the dangling line, and then put on those clamps.

They then covered the lower arms of the pole with orange sheets: https://i.imgur.com/zZ3DFSd.jpg

Does anyone happen to know what the orange sheets are for? They did not use them anywhere else where they grounded the wires.

I've seen lineworkers use orange covers many times, when working near live wires.

The place where they put these orange sheets in your photo looks like a disconnect switch between the wires on either side of the pole. So the wires coming from the left side of your photo are still live, and the disconnect switch itself is still live. Since they would be working near the disconnect switch (to hang the new wire), they put these insulating orange covers for extra protection.

I would also expect that a larger residential inverter could successfully backfeed the load side of a single distribution transformer (i.e. just a few houses). If the line workers are repairing a distribution transformer or its associated hardware, this could be a big deal.

I don’t know if the workers make a habit of physically disconnecting all of the houses that are connected.

I guess the point is that if your residential solar setup attempts to backfeed a dead grid, it will effectively see a short circuit which it, try as it might, will be unable to generate any voltage across, trip and your house is as dead as the rest of the grid.

For this reason, I'd be most surprised if there's a single backfeed system in existence which doesn't isolate your house from the grid once the grid goes down.

Edit: Finally got around to reading the blog post to the end and found that the author makes this exact point in the paragraph following the one quoted in the comment above.

It can also do strange things to outage reporting equipment that assumes power to be flowing a paticular way.

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