Power Line Grounds Near Water

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The hams I talk to seem to feel dry, sandy soils are not at all uncommon. They are the ones telling me it is not uncommon to have difficulty achievin g an earth that is conductive enough to meet the requirements.

I expect the statistic you are citing is not evaluated the same as in the U S. I can't find a source for that number. One number I found says "around 30". I also noticed the number in the forum you found are for deaths "cau sed by electric shocks in the home". I believe the number for the US is al l locations. I'm also not sure what number you are using.

I found from the National Center for Health Statistics (NCHS) 257 deaths fr om electrocution occurred in the US during 2013, the lowest of the steadily declining numbers over the 10 year period.

The only number I can find for the UK is 30 from the "Health and Safety Exe cutive" for an unstated year. I did find another forum with numbers up to

2005 for "fatalities from accidental exposure to electric current in Englan d & Wales" which is 25 in 2003. The number for "fatalities in the home" fo r all of Great Britan in 2006 rises to 13.

Until you find better sources of data, I don't see how you can compare US a nd UK.

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  Rick C. 

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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.

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

I'm late to reading any of this... seems to me the problem is mostly associated with metal boat launches.... so maybe some guide lines/ rules there.

(knowing almost nothing of power engineering), Couldn't we make boat launches that floated the ground some* DC to 60 Hz... and a few harmonics.?

George H.

*some, means (about) a factor of ten in amplitude, 20 dB in power.

th power connections. Some researchers say the ground connection which goe s all the way back to the power line transformer allows power surges to rea ch the dock where it can find its way into the water.

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

Huh? What will that do? Sounds like it would be even more dangerous. But it is only practical if galvanically isolated with a transformer. Then yo u can ground the dock to whatever you want and not worry about common mode transients.

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  Rick C. 

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We went round this mulberry bush here some months ago. Turns out that per capita, slightly fewer folks die over here than OYOSTOP.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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The soil must be very wet in UK and hence have a good conductivity to allow the TT system work as intended.

Assuming the grounding resistance between house and distribution transformer is as low as 10 ohms. A ground fault from 240 V will cause a 24 A ground current. It takes a looong time (minutes) to blow even a

13 A fuse.

In practice RCDs must be used to disconnect the mains voltage fast enough in case of a fault.

For one, that's an unfounded assumption since you can get adequate conductivity in poor locations, it just costs more. The other issue is that there are always variations. I seriously doubt the entire UK has the same soil.

I'm confused. Isn't the neutral bonded to ground at both ends? Blowing a fuse on a ground fault is not why the neutral is grounded.

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  Rick C. 

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If the N and PE are both connected to a ground electrode, then N and PE are also connected together. That sounds like a TN-C-S, in which there is a shared PEN conductor from distribution transformer to house and in the house the PEN is split to N and PE. The splitting point can then be connected to a local grounding electrode, in case the PEN wire is broken.

Most regions of the UK get around 1m of rain per year. Some get more a few get less. My top soil dries out in summer sometimes but the water table is so high that the grounding rod goes deep into a permanent wet clay soil. I have to siphon water out of my garage pit to use it.

Telecoms have problems with junction boxes here filling with water.

Dig down almost anywhere in the UK and you often find water filling your trench. It makes water divining something of a doddle...

It rains enough that chemical corrosion of the grounding conductor is probably more of a worry than it not making good electrical contact.

New UK build is now mostly TN-C-S with neutral and earth combined but where I live the distribution system is rural TT and in older homes the older system was buried armoured cable with the steel sheath as pure earth and separate live and neutral insulated cables inside it TN-S. Made things safer if you put a spade through the buried cable.

Historically the UK kept protective earth and neutral distinct. You could often measure a modest potential difference between neutral and earth. I have seen my neutral rise quite a way from earth when a single phase went down under a fault condition recently. LED bulbs, TV and computers worked fine but classic filament bulbs glowed a dim orange.

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Regards, 
Martin Brown

Speaking of fish, the Pacific Intertie has ground grids at each end in case they must dump a few gigawatts somewhere....

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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.

ut it is only practical if galvanically isolated with a transformer. Then you can ground the dock to whatever you want and not worry about common mod e transients.

More with the galvanic BS. No one in the code talks about "galvanic" anything with regard to earthing.

This thread as usual has moved on to BS and the absurd. Those guys in the article gave a solution. Disconnect the dock connection to the equipment grounding conductor and use an earthing system at the dock instead. Alternatively, you could just create an earthing electrode system at the dock and tie it to the eqpt grounding conductor and that would likely solve it too. Neither is code compliant.

Sounds like the IT system, As long as you have a ground on only one phase, the system works normally. You just get an alarm of a ground fault so it is a good idea to fix the ground fault before a ground faults develops on an other phase.

Galvanic isolation is used with Safety Extra Low Voltage (SELV) supplies (less than 50 Vac). Often required when working inside a metallic tank.

Cursitor Doom has clearly never tried to read E.C.Snelling on Soft Ferrites .

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The grammar might have been okay, but it was a pedagogic disaster.

The main advantage that older text books have is that the junk never got re printed, and the good stuff went through lots of editions.

And I do have to wonder what kinds of school Cursitor Doom thinks that I mi ght approve of. I can't remember ever posting anything about schools here - beyond that universal education is a good thing, and that American primary and secondary schools have very variable funding from one school district to the next.

If the kids come out able to read, write and do arithmetic, the school has done it job, and the kids are in a state where they can learn more for them selves by reading books - if they are a bit brighter than Cursitor Doom and can recognise nonsense when they run into it (which he clearly can't) and can chuck the bad books.

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Bill Sloman, Sydney