boat dock shocks swimers

[kwired]

..The ground around the house is all rock and the power plant ground puts power in to the lake. with very little dirt to ground, this is a promblem all around the lake. The land around the lake is very rocky.

And how is this different from how a typical concrete swimming pool is constructed other than we don't have equipotential grounding grid intentionally installed in the lake?

Most often the problem is from the utility neutral. They use the same conductor for neutral and ground. It results in the dock becoming part of the neutral return path...

The problem is that you have a certain potential at a particular point at the lake. Then you take the EGC for the electric equipment on the dock and put it in close proximity to the lake. Remember that the other end of this EGC conductor is connected to earth someplace else that will be at a different potential than the water in the lake. By tying it to metal parts within reach of the water you now can touch both points at same time subjecting you to whatever voltage difference there is. A grounding electrode near the dock will bring the voltage from the water to the EGC much closer to zero than if the nearest GEC is hundreds of feet away. If dock is fed by a service or feeder it should have a grounding electrode anyway.

 

[don_resqcapt19]

If the source of the voltage is the voltage drop on the utility grounded conductor, additional grounding electrodes will not change anything...except for a very small area very close to the grounding electrode. The pool perimeter bonding is not based on getting rid of the voltage...it is based on elevating everything to the same voltage. That is a bit easier to do with a pool that with the water in a lake or river.

 

[kwired]

If the source of the voltage is the voltage drop on the utility grounded conductor, additional grounding electrodes will not change anything...except for a very small area very close to the grounding electrode. The pool perimeter bonding is not based on getting rid of the voltage...it is based on elevating everything to the same voltage. That is a bit easier to do with a pool that with the water in a lake or river.

That is what I was thinking was to bring everything to same voltage, but you are right about it only bringing it to same voltage over a pretty small area. Since problem is likely voltage drop on POCO neutral, maybe OP can get the POCO to put in a grounding grid in the whole lake like is done for swimming pools or they could just try to balance the load better.

Hopefully they have verified that there is no bad connection on the neutral someplace.

 

[don_resqcapt19]

... or they could just try to balance the load better. ...

Or they could use line to line connections to feed the prirmary of their transformers, in place of the line to neutral connections that they often use.

 

[Matthew_B]

Or they could use line to line connections to feed the prirmary of their transformers, in place of the line to neutral connections that they often use.

Utilities are going away from delta connections as much as possible. They want to avoid ferroresonance problems, and with a solidly grounded Y connection and single phase pigs they completely avoid ferroresonance.

 

[don_resqcapt19]

Utilities are going away from delta connections as much as possible. They want to avoid ferroresonance problems, and with a solidly grounded Y connection and single phase pigs they completely avoid ferroresonance.

And provide more voltage to energize our pool water......