Power Line Grounds Near Water

[snip]

At kilovolt potentials, even pacing can be dangerous. We do Injection Polarization mineral surveys, at levels up to 10KV. Our crews are instructed to stand away from the equipment, feet together, and not to walk about while a test is in progress.

The same applies to people walking near downed power lines...

If you're talking about 120/240v, then yes, the risk is much lower.

Reply to
Randy Day
Loading thread data ...

We're all used to working with low to moderate voltages with little more than a minor tingle during accidental contact. So, we're naturally skeptical when presented with evidence of low-voltage electrocution.

However, if you're immersed in water for some time, your waterlogged skin no longer provides its normal high-resistance barrier to current flow. Under these conditions, the effective resistance (from outstretched hands to feet) of a human drops to the order of 300 ohms or so. Since a current of 50 - 100 mA at 50/60 Hz can induce ventricular fibrillation, a potential of only 15 - 30 AC volts could kill you. And, since only 18-20 mA is sufficient to induce respiratory arrest, less than 6 volts AC across your body could potentially cause you to drown. Some sobering information from an open source journal:

formatting link

Reply to
Bert Hickman

ing," Harrington said. "We then put the lift down in the water as it had be en described when the shock happened, and the device lit right up."

d

Can you even read? I didn't say people could not be shocked at docks, I acknowledged that they could be. What you can't understand is that the example cited, someone getting a shock when the lift motor is energized and not getting shocked when it's not, indicates a FAULT. And of course when you have faults you can be shocked and killed, especially if there are multiple faults and you don't have GFCI which any responsible dock owne r would have today. The guy worrying about the docks, what is he going to solve? There never has been a reqt in NEC that old homes and facilities have to be brought up to current code. Putting in GFCI where they don't exist would likely save far more lives than his new code. And that code, like almost all the rest of the code, would apply going forward, not to what's out there already.

main current flowing, but transients that cause voltages to show up on the normal routes. The earth ground will have a connection to neutral at the h ouse. Any voltage showing up along the resistance of the neutral can show up on the >protective earth wire which can lead right to the water.

ROFL

Was it someone who hijacked your computer that started off this thread with this:

"It seems a bit odd and the drawing shows ground connections at the pole, t he house and at the dock. It's hard to imagine that even without any defec ts any sort of voltage would be transferred to the water. "

First you say that you can't imagine how someone at a dock could get a shock without a fault, so I and other posters had to explain to you how that's possible because of the neutral being grounded and now you're ex plaining it to us?

as perfect and grounds as perfect.

No shit Sherlock,

Who ever said it was?

The transients in question are short duration but high current which then challenge the assumptions we commonly make regarding our utilities.

BS. It's not really about transients. I could put 100 amps worth of stati c light bulbs and coffee pots on the house circuits. And because the eqpt grounding conductor is tied to earth ground and the neutral, a person standing on the dock with wet feet is an alternate path for some of that current. How much, what voltage develops, depends on the relative resistance of the neutral to the transformer, the resistance of the house grounding electrode system, the resistance of the path from the grounding electrodes back to the transformer and the resistance of the person standing at the do ck and that path back to the transformer.

And the lift motor causing a shock isn't transients. It's a fault with the lift motor, because otherwise that lift motor is no different than the AC compressor coming on or the coffee pot being plugged in at the house.

You make much money with all that spamming?

Reply to
Whoey Louie

Why of course. And the cite says that a person soaked with water, immersed in water, still has a resistance of 300 ohms and that it takes 100ma to cause cardiac arrest. Do the math. If you have some examples of people dying from being exposed to 15 volts, I'd be happy to see them. And if you can read, I said I believed it might be possible, under some special circumstances.

Reply to
Whoey Louie

with power connections. Some researchers say the ground connection which g oes all the way back to the power line transformer allows power surges to r each the dock where it can find its way into the water.

le, the house and at the dock. It's hard to imagine that even without any defects any sort of voltage would be transferred to the water.

s

ing

ed.

ve

ectrode

mer,

be

the

ry

e

ing" electrical systems. Everything done by grounding can be accomplished by using a "safety" wire which is essentially a backup neutral. As long as neutral faults can be detected such as by GFCI, why does connecting to lit eral "earth" make a difference?

Lightning is one big thing. Or a fault where the high voltage primary contacts the low voltage side. With one side grounded, it limits the fault voltage. With no earthing, you'd have 12KV going into homes, searching for whatever path it can find to complete a circuit.

t

tage

lls,

that.

I believe the voltages referred to in the article are measured across the body, not at the source.

In which case it would take even higher circuit voltage.

Reply to
Whoey Louie

thing," Harrington said. "We then put the lift down in the water as it had been described when the shock happened, and the device lit right up."

uld

e

d,

d
!

Ok, you didn't read the description of the issue very well. The article ta lked about "with the lift in the water", not energized. The metallic cable s of the lift conducted the ground circuit to the water.

ner

He isn't trying to change the NEC. I think he has given up on that. He is lobbying the Virginia state legislature who sets the code for the state of VA, not the NEC.

Actually, if you think a GFCI will do the job, you didn't read the article. The current isn't coming from a defect connecting the live wire to ground . The problem seems to be voltage transients in the ground wire itself. T he researchers believe this is from a large current spike creating voltage on the neutral which is tied to the ground wire.

e main current flowing, but transients that cause voltages to show up on th e normal routes. The earth ground will have a connection to neutral at the house. Any voltage showing up along the resistance of the neutral can sho w up on the >protective earth wire which can lead right to the water.

th

the house and at the dock. It's hard to imagine that even without any def ects any sort of voltage would be transferred to the water. "

explaining it to us?

I was trying to say I've not seen any docks with a ground connection. I do n't have power on my dock. But I've never seen a ground connection on any dock I've been on. I would have seen one at some point.

rs as perfect and grounds as perfect.

n challenge the assumptions we commonly make regarding our utilities.

tic

s

dock

So everything the guy said is a lie?

There are none so blind who will not see.

--
  Rick C. 

  --+ Get 1,000 miles of free Supercharging 
 Click to see the full signature
Reply to
Rick C

So you acknowledge that 15 can be a problem??? I'm confused...

Your 100 mA is for a fatal electric shock stopping the heart. A lower current causes a severe shock that can cause a person to drown, not by stopping the heart. I think the article says that.

Maybe you should try reading it???

--
  Rick C. 

  -+- Get 1,000 miles of free Supercharging 
 Click to see the full signature
Reply to
Rick C

s with power connections. Some researchers say the ground connection which goes all the way back to the power line transformer allows power surges to reach the dock where it can find its way into the water.

pole, the house and at the dock. It's hard to imagine that even without an y defects any sort of voltage would be transferred to the water.

eas

ed

aking

ized.

give

g

ng

electrode

ormer,

f
n

e

s be

t the

very

the

d

ou

nding" electrical systems. Everything done by grounding can be accomplishe d by using a "safety" wire which is essentially a backup neutral. As long as neutral faults can be detected such as by GFCI, why does connecting to l iteral "earth" make a difference?

You are talking about a 12 kV line that has the other side grounded. If no ne of this were grounded, it wouldn't matter if you touch the wire. That's why a lineman or a squirrel can touch a hot wire as long as he isn't groun ded. If the neutral wasn't grounded what would complete the path?

But the lightning issue makes sense.

ght

oltage

bells,

m that.

. I believe the voltages referred to in the article are measured across th e body, not at the source.

Yeah, what's your point?

--
  Rick C. 

  -++ Get 1,000 miles of free Supercharging 
 Click to see the full signature
Reply to
Rick C

Are you kidding? The author, like 99% of the population, clearly doesn't know the difference between current and voltage. I'd assumed everyone here would at least know that, but I never cease to be amazed. :/

--
This message may be freely reproduced without limit or charge only via  
the Usenet protocol. Reproduction in whole or part through other  
 Click to see the full signature
Reply to
Cursitor Doom

There is also the critical issue that (in the UK at least) mains live/ line/hot wires are earth-referenced so you can get electrocuted just be touching one hot wire. That's why those of us that work on higher voltage equipment use isolation transformers to 'strip-off' the earth reference.

--
This message may be freely reproduced without limit or charge only via  
the Usenet protocol. Reproduction in whole or part through other  
 Click to see the full signature
Reply to
Cursitor Doom

Try again with wet hands, if you get them propperly wet with impure water (maybe add a little table salt) 5V should be enough to suprise you.

I read of someone dying while working on a 36V wind generator during a rainstorm, but it's possible that they triggered a load dump.

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

So if you cut the ground wire and fit a GFCI on the line that could fix it, but you'd need a GFCI that's designed to fail safe.

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

As long as you are fully submerged and the water has at least some conductivity (not distilled water), all your body parts are nearly at the same potential. So even if your skin resistance drops to 300 ohms, not much current can flow.

Of course, if you touch e.g. a ladder that is not in the water and the ladder has an elevated potential above water potential, there is a risk.

Reply to
upsidedown

By this point the conductivity of the electrolyte becomes a factor that needs to be considered as well I would guess.

--
This message may be freely reproduced without limit or charge only via  
the Usenet protocol. Reproduction in whole or part through other  
 Click to see the full signature
Reply to
Cursitor Doom

cks with power connections. Some researchers say the ground connection whi ch goes all the way back to the power line transformer allows power surges to reach the dock where it can find its way into the water.

e pole, the house and at the dock. It's hard to imagine that even without any defects any sort of voltage would be transferred to the water.

areas

ar

ated

taking

rgized.

o give

ing

ving

e

g electrode

ll

sformer,

of

an

e

the

ems be

at the

s very

n the

uld

you

ounding" electrical systems. Everything done by grounding can be accomplis hed by using a "safety" wire which is essentially a backup neutral. As lon g as neutral faults can be detected such as by GFCI, why does connecting to literal "earth" make a difference?

none of this were grounded, it wouldn't matter if you touch the wire. That 's why a lineman or a squirrel can touch a hot wire as long as he isn't gro unded. If the neutral wasn't grounded what would complete the path?

What would complete the path is something, unpredictable, on the other side , or in the case of 3 phase, sides. With the primary shorted to the service going to a house, you'd have 12KV on one hot trying to find a path and it would be unpredictable. Starting with that 12KV far exceeds the insulation rating of the wire, eqpt, appliances, etc. So, who knows what and where the path would be. That's one reason grounding is preferred. With the path being one side of the service and/or the grounded metal and earth, the situation becomes far more predictable. That 12KV short to the service at the utility pole would quickly find a path, arc over, before mos t of it ever got to the house. Grounded systems make it easy to find faults, trigger on them to cut off power, etc. too. Isolated systems if used in general areas, like to power homes, are very unpredictab le when it comes to faults, which is why they are confined to special situations, eg specific industrial needs, where those possible faults can be determined and appropriate protection used.

might

voltage

r bells,

rom that.

er. I believe the voltages referred to in the article are measured across the body, not at the source.

That if that's the case, then it takes even higher stray voltage to be lethal.

Reply to
Whoey Louie

e:

nothing," Harrington said. "We then put the lift down in the water as it ha d been described when the shock happened, and the device lit right up."

would

be

n

zed,

and

e

re!

he

talked about "with the lift in the water", not energized. The metallic cab les of the lift conducted the ground circuit to the water.

I read that to mean that it was while it was being lowered and the lift was powered. But I agree that they likely meant just the metal of the lift creating the problem, so in that case, it's just a ground loop issue, not a fault with the lift circuit.

owner

o
s

is lobbying the Virginia state legislature who sets the code for the state of VA, not the NEC.

Doesn't matter, same thing still applies, unless VA is doing something very unusual. I've yet to hear of a state where when new code is adopted they typically make it apply retroactively to what is out there. For 99% or mor e, they don't. You can still hook up a three wire circuit to a dryer, using the neutral as the eqpt ground, for example, all across the US, AFAIK. That changed in the code for new installations decades ago.

e,

e.

I didn't say a GFCI would "do the job". I specifically addressed the lift issue and said that if the water is becoming energized when the lift motor is activated, then a GFCI would trip and that any responsible owner of a dock today would have circuits there protected by GFCI.

The current isn't coming from a defect connecting the live wire to ground. The problem seems to be voltage transients in the ground wire itself. The researchers believe this is from a large current spike creating voltag e on the neutral which is tied to the ground wire.

It's interesting that these researchers didn't research all that much, from what is presented here. Notably absent is any measurement of the grounding electrode system resistance at the house, or even if there is a code compli ant grounding electrode system at the house that is properly bonded to the neutral. Or any attempt to identify the source of these transients, ie is it eqpt in the house pr something else. They appear to want to just look at the dock. For all we know, there could be various problems back at the panel and service. But the main point here is that whatever brief imbalance a transient can create, you'd expect that worse could be created by static loads that are on one hot leg. Put 100 am ps worth of tea pots and heaters on one leg and I'd bet that creates a higher voltage that's constant at the dock.

the main current flowing, but transients that cause voltages to show up on the normal routes. The earth ground will have a connection to neutral at t he house. Any voltage showing up along the resistance of the neutral can s how up on the >protective earth wire which can lead right to the water.

with

e, the house and at the dock. It's hard to imagine that even without any d efects any sort of voltage would be transferred to the water. "

e explaining it to us?

Say what? All circuits at docks, pools, etc have had to have a ground connection and all metal bonded to it for the better part of the last century.

n any dock I've been on. I would have seen one at some point.

You've never seen a three prong receptacle? Or are you talking about a ground rod at the dock bonded to the electrical system? If it's the latter , you should know why you haven't seen it, per the article it's not only not required, it would be a code violation.

tors as perfect and grounds as perfect.

hen challenge the assumptions we commonly make regarding our utilities.

tatic

des

e dock

Wow, where do you come up with these things.

Reply to
Whoey Louie

ing," Harrington said. "We then put the lift down in the water as it had be en described when the shock happened, and the device lit right up."

d

If you pay attention to what they wrote they seem to be finding, not the m ain current flowing, but transients that cause voltages to show up on the n ormal routes. The earth ground will have a connection to neutral at the ho use. Any voltage showing up along the resistance of the neutral can show u p on the protective earth wire which can lead right to the water.

as perfect and grounds as perfect. This is not a problem caused by light bulbs and coffee pots.

Explain to us how a static 100A neutral current at the panel from light bulbs and coffee pots isn't going to create a voltage at the dock. Part of it will flow through the neutral to the utility, part will flow through the grounding electrodes at the house back to the utility and part of it will flow through the eqpt grounding conductor to the dock and through whatever paths it finds there to earth, including any humans. And it's static, not just an impulse. I agree transients of lesser currents could probably create the same voltage because we're dealing with impedances, but static loads would be an issue too.

Missing in all this by these "researchers" is any measurement of what's going on at the house panel. For example, what was the resistance of the grounding electrode system? What did that consist of? Did they do anything to try to identify the source of these transients? Cam they be seen at the panel? It's particularly hard to imagine how a typica l transient from the power line is making it's way all the way to the dock. From that article, they are focused only on the dock. What they are proposing could be a good idea. But if it's a good idea there, then why not at pools? I don't see people being shocked and electrocuted at swimming pools and all the metal there is, or is supposed to be, bonded to the ground system of the house. So, you'd think there would be the same thing happening.

The transients in question are short duration but high current which then challenge the assumptions we commonly make regarding our utilities.

From that article there is no indication they measured what the currents of any of the transients in question were, nor any attempt to identify the source.

Reply to
Whoey Louie

They already established the threshold for their conditions (person in water) was about 15 volts. You, of all people, should know E = I*R. So if the R is constant, current is proportional to voltage.

Why do people get so wigged out when someone talks about dangerous voltages. I bet there's an XKCD cartoon about this.

--
  Rick C. 

  +-- Get 1,000 miles of free Supercharging 
 Click to see the full signature
Reply to
Rick C

the

d

e talked about "with the lift in the water", not energized. The metallic c ables of the lift conducted the ground circuit to the water.

t, but

Huh? A GFCI is designed to detect unbalance of current in the neutral and hot wires. I don't follow what you are saying about cutting the ground wir e. Where do you cut it? I believe this no longer adheres to code no matte r what... unless you are talking about providing a separate ground rod for the dock.

--
  Rick C. 

  +-+ Get 1,000 miles of free Supercharging 
 Click to see the full signature
Reply to
Rick C

That was the reasoning I used to say dropping a radio into the bath water would be safe. But that is not true. The conductivity of water is enough to cause problems, but not enough to essentially be a short circuit around your body.

--
  Rick C. 

  ++- Get 1,000 miles of free Supercharging 
 Click to see the full signature
Reply to
Rick C

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.