Dock on the lake with ground current

[winnie]

There are two possible sources of the current flowing in the lake: neutral current from the high voltage distribution system supplying power to the distribution transformers, or a fault to earth on the low voltage (120/240V) usage side of the power distribution system.

We are quick to jump to the conclusion that the problem is the high voltage neutral, because as normally designed these systems always inject a little bit of current into the soil.

However faults from the low voltage side of things to soil can also inject current into the ground and water. This current will be finding its way back to the neutral of the distribution transformer via all of the various grounding electrodes.

A specific risk for this is well pump wiring. An underground well casing is an excellent grounding electrode. If the well casing is not properly bonded back to the service, and the well wiring faults to the case, then the well can inject quite a bit of current into the soil.

Another known risk are pumps in lakes used as water sources. If there isn't proper bonding, and there is a fault, then the pump can inject current into the surrounding water. There was a thread recently about drowning risks from these pumps.

-Jonathan

 

[kwired]

There are two possible sources of the current flowing in the lake: neutral current from the high voltage distribution system supplying power to the distribution transformers, or a fault to earth on the low voltage (120/240V) usage side of the power distribution system.

We are quick to jump to the conclusion that the problem is the high voltage neutral, because as normally designed these systems always inject a little bit of current into the soil.

However faults from the low voltage side of things to soil can also inject current into the ground and water. This current will be finding its way back to the neutral of the distribution transformer via all of the various grounding electrodes.

A specific risk for this is well pump wiring. An underground well casing is an excellent grounding electrode. If the well casing is not properly bonded back to the service, and the well wiring faults to the case, then the well can inject quite a bit of current into the soil.

Another known risk are pumps in lakes used as water sources. If there isn't proper bonding, and there is a fault, then the pump can inject current into the surrounding water. There was a thread recently about drowning risks from these pumps.

-Jonathan

Other than if you are swimming in vicinity near such pumps are they really any more risk than a submersible in a well casing on the shore? Or even jet pump type shallow well on the shore with metallic piping as the well?

Any of those things will have a voltage gradient in the vicinity of said "thing" and further away you get the more things become same as true earth potential. Most these that gradient drops off in pretty short distance, which is the thing that makes a hazard when near them as you can touch different potential zones at the same time.

 

[ptonsparky]

I wonder how many are hung on plastic with no EG.
Found more than one ’leaking’ back in my stray voltage & dairy barn days.

 

[tortuga]

I spoke with the POCO who confirmed he has personally checked all the wires from our point (end of the line) back to the substation. He confirmed this issue tends to be worse when it’s dry (lower earth conductivity, already poor due to rocky soil) and we’ve been in a 2-3 week hot and dry spell. It doesn’t help that in the 3 communities served by this long single line homes are continually being expanded or rebuilt so electrical load is going up.

Can you post a pic of one of the distribution transformers? Do we know is this overhead or underground? Is the primary is wired Line to neutral?

 

[winnie]

Other than if you are swimming in vicinity near such pumps are they really any more risk than a submersible in a well casing on the shore? Or even jet pump type shallow well on the shore with metallic piping as the well?

Any of those things will have a voltage gradient in the vicinity of said "thing" and further away you get the more things become same as true earth potential. Most these that gradient drops off in pretty short distance, which is the thing that makes a hazard when near them as you can touch different potential zones at the same time.

I don't know the relative risks, and am not sure there is good data available.

You might poke around the Army Corps of Engineers to see if they have data; they do have a policy prohibiting submersible pumps in lakes:

https://www.swf-wc.usace.army.mil/Belton/images/ElectricSubmersiblePumpInformation.pdf

 

[tortuga]

Here is a interesting youtube video where a guy experiments with a few voltages thru ground, note only the 120 volt would apply to residential as residential here is split phase with only 120 to ground. I think he uses a 75VA control transformer in reverse appears to use a distance of 200'.

 

[kwired]

I don't know the relative risks, and am not sure there is good data available.

You might poke around the Army Corps of Engineers to see if they have data; they do have a policy prohibiting submersible pumps in lakes:

https://www.swf-wc.usace.army.mil/Belton/images/ElectricSubmersiblePumpInformation.pdf

Often the "water table" below land is basically same water as what it in the nearby lake or stream, especially in my neck of the woods. This mostly goes for shallow wells that are capable of being pumped from with a jet pump.

There are deeper wells that get into better quality water.

I still don't really see that there should be that much difference in effects to someone swimming in the lake. These things have a voltage gradient in the water or earth that is nearby exposed metallic objects that are at other than earth potential, but it always drops off pretty rapidly. If you are at least 10 feet away from items operating at just 2 to 10 volts to earth you shouldn't be exposed to anything that should be harmful or likely won't even be able to feel anything.

 

[GoldDigger]

There are two possible sources of the current flowing in the lake: neutral current from the high voltage distribution system supplying power to the distribution transformers, or a fault to earth on the low voltage (120/240V) usage side of the power distribution system.

We are quick to jump to the conclusion that the problem is the high voltage neutral, because as normally designed these systems always inject a little bit of current into the soil.

However faults from the low voltage side of things to soil can also inject current into the ground and water. This current will be finding its way back to the neutral of the distribution transformer via all of the various grounding electrodes.

A specific risk for this is well pump wiring. An underground well casing is an excellent grounding electrode. If the well casing is not properly bonded back to the service, and the well wiring faults to the case, then the well can inject quite a bit of current into the soil.

Another known risk are pumps in lakes used as water sources. If there isn't proper bonding, and there is a fault, then the pump can inject current into the surrounding water. There was a thread recently about drowning risks from these pumps.

-Jonathan

A fault to casing in a well with a submersible pump can also potentially draw enough extra current to substantially raise your electric bill without tripping any OCPD for the pump. Some sort of ground fault protection (not as sensitive as GFCI, since some stray current capacitive current from long conductors immersed in water could easily trip those) would be a good idea for several reasons.
The higher the standing water level above the pump, the worse the potential problem will be.

 

[gaspower]

This is a mountain lake. The soil is rocky, the lake shoreline is steep (30-40' water depth in the boat slip of my dock) and the wells are deep. There is only one well within 0.5mi of my dock and it serves a 10k gallon storage tank so it runs intermittently. It would only be able to inject current into the ground when the pump is running and I have not observed any intermittent behavior.

never say never but the POCO also believes it is the high voltage neutral causing the issue.

Can you post a pic of one of the distribution transformers? Do we know is this overhead or underground? Is the primary is wired Line to neutral?

The communities are underground with pad mount transformers 14.4kV to 240VAC and the service to the community from the 25mi away substation is overhead. I'll take pics Wednesday when I am back up there.