Voltage on utility neutral

[Power Solutions]

Recently I have found 2 customers with 1 to 3 volts ac on the neutral from the utility to earth and drop disconnected from the home.
Both were getting shocked when exiting a pool or hot tub.
The utility cannot seem to fix the problem.
What causes this? Is it a poor ground at a transformer?
Dj

 

[mivey]

The utility cannot seem to fix the problem.
What causes this? Is it a poor ground at a transformer?
Dj

The utility neutral is a conductor and will experience a voltages drop so it is not a matter of "fixing" it in that sense. You could drive 1,137,356 ground rods at your location and the neutral to earth voltage would be the same.

 

[mivey]

While you did not ask, your best solution will probably be to put in an equipotential grid at the pool and hot tub.

If you feel like chasing the other avenues (low probability of success/action): Is the primary 3-phase? Is the primary overhead or underground? How far are you from the utility substation? Would the utility put in a neutral isolator (would also need to isolate phone, CATV, metal water pipe, etc)?

 

[cowboyjwc]

The problem with the utility neutral carring a small load is that it is hooked up to all of the other houses around so there is sure to be some unbalanced load coming back.

I agree with mivey about the pool bonding. Now if the utilities are underground you could have a leak.

 

[electricalperson]

its stray voltage. mike holt had a video about it. check it out on his website. your pool isnt bonded properly. if you bond the pool properly and come from anything metal thats bonded to the earth you will read voltage. use an analog meter with a low 2.5v scale or something

 

[gar]

100718-1242 EST

Power Solutions:

What does this mean

Recently I have found 2 customers with 1 to 3 volts ac on the neutral from the utility to earth and drop disconnected from the home.

?

Are all three wires from the utility disconnected from anything at the home? Meaning in particular is the neutral disconnected from the home? This is my assumption from your statement.

Is the voltage to earth measured from the neutral end of the utility drop at the house to the house neutral-EGC-grounding point? If yes, then there is utility or somebody else's current flowing thru the earth.

With the utility neutral disconnected from the home the utility neutral becomes a test lead to the center tap of the transformer. You have not said, but the distribution system is probably a Y with the primary neutral connected to the secondary neutral.

With this disconnected state it would be useful to know what if any current is flowing in the grounding wire at the pole to the pole ground rod.

If you were to measure the voltage from the open end of the utility neutral at the home to actual contact with the ground rod at the pole it should be very close to 0.

Assuming there is current flow from the pole grounding wire to the earth, then if you measure from said wire to spots in the earth close to the ground rod the voltage should drop off as you move away from the ground rod. Be careful. At times this might be on the order of the roughly 10 V you have seen as a peak. Use a high impedance DVM, like the Fluke 27.

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