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re: Why is the electricity still on in severely flooded areas?
Posted on 8/28/17 at 12:02 am to airfernando
Posted on 8/28/17 at 12:02 am to airfernando
quote:
electricity always takes the path of least resistance.
No, it prefers the path of least resistance. It will take any path available.
I only work on commercial/large residential electrical systems (almost exclusively 480V and lower, sometimes 13,800V) and not the distribution side (i.e. Entergy's lines, 13.8KV and higher), so I really don't know for sure how this is handled on a large scale. I thought it might be with large ground fault breakers at substations (similar to the GfI receptacles in bathrooms), but I'm pretty sure that distribution systems don't have neutral conductors, so I'm not sure how that would work. After a quick googlering, apparently substations DO have GFI protection, but that doesn't make sense to me given the lack of neutral and I don't feel like reading 50+ page essays on how it works. Sorry.
1
Posted on 8/28/17 at 12:02 am to theunknownknight
quote:
So 220 electricity is flowing through the water? No one seems to feel the effects? :-|
Posted on 8/28/17 at 12:04 am to wallowinit
Transmission stations aren't likely affected as they are usually built on higher land.
It's likely that transformers are on the pole, if the lines aren't down there won't be any issues with service.
Cable and Telco are almost all underground.
If your house is flooded and there's still power that only means that the breakers haven't seen enough amperage to pop the circuit breaker.
Amperage requires a load, and unless the circuit is over loaded it will stay on.
The idea of water carrying electricity depends on several factors, mostly related to salinity.
It you are 8 inches underwater and complete the circuit, you're toast, but if the 120/240 cut is going where it's supposed to go it shouldn't fail, or hurt you, unless you complete the circuit.
Now, the 14.4 kv on the line before the transformer, that's a different story.
It's likely that transformers are on the pole, if the lines aren't down there won't be any issues with service.
Cable and Telco are almost all underground.
If your house is flooded and there's still power that only means that the breakers haven't seen enough amperage to pop the circuit breaker.
Amperage requires a load, and unless the circuit is over loaded it will stay on.
The idea of water carrying electricity depends on several factors, mostly related to salinity.
It you are 8 inches underwater and complete the circuit, you're toast, but if the 120/240 cut is going where it's supposed to go it shouldn't fail, or hurt you, unless you complete the circuit.
Now, the 14.4 kv on the line before the transformer, that's a different story.
This post was edited on 8/28/17 at 12:08 am
Posted on 8/28/17 at 12:08 am to THRILLHO
quote:most substations will have a resistance grounded neutral, that will limit the ground current to something like 200-400A.
apparently substations DO have GFI protection, but that doesn't make sense to me given the lack of neutral and I don't feel like reading 50+ page essays on how it works. Sorry.
Posted on 8/28/17 at 12:08 am to wallowinit
quote:
BINGO! We have a winner! Electricity takes the path of least resistance. It's not going to jump out and get you even when submerged in a flood. I've been through many floods so that's not just speculation.
And you would be wrong, a power line in the water will energize the water in the same manner as a lightning strike. The water will be energized in expanding concentric circles with the voltage decreasing with distance away from the energized conductor. If by walking or swimming in the water your body were to span enough area that there was a difference of electrical potential between two parts of your body current would flow through your body and possibly result in electrocution. The effect is known as "step potential", and can also occur when walking on the ground near a downed power line.
This post was edited on 8/28/17 at 12:11 am
Posted on 8/28/17 at 12:08 am to LSUGrad9295
quote:
r they bury their cables.
Posted on 8/28/17 at 12:22 am to EA6B
My Bad, misread your post and thought you were contesting the person that said current flows through all paths available. You're correct
This post was edited on 8/28/17 at 12:47 am
Posted on 8/28/17 at 12:26 am to busbeepbeep
quote:
most substations will have a resistance grounded neutral, that will limit the ground current to something like 200-400A.
But they don't have a grounded conductor going to each transformer fed by the phase conductors. So there's no way to measure outgoing current vs. incoming current to see that current is going places that they don't want it to go in the case of a bad flood. I have an idea of what happens on the individual home/business level in flooding, but not sure how substations are affected with the random shite that they feed between (stoplights, streetlights, etc...)
Posted on 8/28/17 at 12:33 am to DrSteveBrule
The exponential decrease in power on a 120/240 ckt would be enough given the environment to allow for a person to walk around without much fear. Lots of loss in that environment, especially in a well grounded home.
Again, you put your finger in the wrong place and you're toast.
The fear in this environment, is getting close to a line before the transformer on the ground/in the water. Even then there would be quite a bit of loss in a freshwater environment. Relatively speaking of course.
Still, stay the frick away from that line, it will roast you before you know it.
Again, you put your finger in the wrong place and you're toast.
The fear in this environment, is getting close to a line before the transformer on the ground/in the water. Even then there would be quite a bit of loss in a freshwater environment. Relatively speaking of course.
Still, stay the frick away from that line, it will roast you before you know it.
This post was edited on 8/28/17 at 12:34 am
Posted on 8/28/17 at 12:34 am to THRILLHO
quote:they can sense the residual current from the 3 phases, but usually there's also a ground conductor on the feeders unless an ungrounded system
So there's no way to measure outgoing current vs. incoming current to see that current is going places that they don't want it to go in the case of a bad flood.
Posted on 8/28/17 at 12:46 am to EA6B
(no message)
This post was edited on 8/28/17 at 12:47 am
Posted on 8/28/17 at 12:50 am to EA6B
quote:
a power line in the water
of course a "power line" is a whole 'nother story.
No one has bare power power lines running through their living room. The OP was obviously referring to receptacles and such.
This post was edited on 8/28/17 at 12:54 am
Posted on 8/28/17 at 1:11 am to wallowinit
quote:
of course a "power line" is a whole 'nother story. No one has bare power power lines running through their living room. The OP was obviously referring to receptacles and such.
I used "powerline" as a generic term for any electrical conductor. The effect of "step potential" applies equally to 120 volt circuits in a living room. Many people have been killed in water that was energized by a 12o volt circuit, it is almost too common around boat docks where there are electrical outlets and lighting circuits. As a result of poor maintenance a conduit with a outlet attached will break loose and fall in the water, and many are not properly installed with GFI protection, the water becomes energized and swimmers that happen to get close enough are electrocuted.
The first page of my google search had about 25 people killed this way in recent times.
LINK
“As they were swimming toward the dock, within somewhere between the 5-to-10-foot range, is when they started feeling like they couldn’t swim,” Johnson recalled"
"Even a low level of electric current in the water can be extremely hazardous or fatal to a swimmer -- especially in freshwater, where experts say the voltage will “take a shortcut” through the human body."
“There is no visible warning or way to tell if water surrounding a boat, marina or dock is energized or within seconds will become energized with fatal levels of electricity,” the non-profit Electric Shock Drowning Prevention Association reports.
This post was edited on 8/28/17 at 1:15 am
Posted on 8/28/17 at 2:06 am to EA6B
It's obviously a threat.
If you're riding in an ungrounded boat, the threat is almost zero. Same with swimming in waters with 120 live in the water.
In your example the swimmer would have had to have grounded themselves. A dock would be grounded enough for a lethal shock. I'd wager that in most of those cases, there was a large metal boat dock involved.
The dock becomes the load for a poorly grounded circuit or one with a faulty GFE that doesn't trip.
You touch the dock while in the water, or anything connected to the dock, you're done.
If you're riding in an ungrounded boat, the threat is almost zero. Same with swimming in waters with 120 live in the water.
In your example the swimmer would have had to have grounded themselves. A dock would be grounded enough for a lethal shock. I'd wager that in most of those cases, there was a large metal boat dock involved.
The dock becomes the load for a poorly grounded circuit or one with a faulty GFE that doesn't trip.
You touch the dock while in the water, or anything connected to the dock, you're done.
Posted on 8/28/17 at 2:25 am to theunknownknight
240 ??
Posted on 8/28/17 at 2:36 am to EA6B
Such a great point. My cousin was killed by this at a lake in Ridgeland,MS when I was younger.
Posted on 8/28/17 at 7:01 am to airfernando
quote:
electricity always takes the path of least resistance.
Wrong. The current splits and is inversely proportional to impedance (resistance).
Posted on 8/28/17 at 7:08 am to theunknownknight
Because if they did, the media would squeal that the evil electric company, republicans and Trump hate poor people, pets and minorities.
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