15v to ground

[Kessler4130]

Hello,

My question is for a friend who works for a county maintenance department, he is also a licensed Master Electrician. There are 15 volts to ground on basically everything that is metal in a pumping station, this pumping station is connected with 5 or 6 others which are all showing the same conditions. I know the information I have is vague and more is probably needed, I am just curious is anyone else has encountered this and would know where to start in isolating the cause.

The voltage they are reading is from the metal to earth (actual soil) now I do not know what method or metering device being used to do this, it was noticed by an HVAC mechanic who was working on an A/C unit. The building is also an old nike missile site from the cold war if that is relevant in anyway. They have checked thier GEC's and neutrals to make sure everything is properly grounded, bonded and of sufficient torque, the problem remains unchanged.

I will post more information as it is available, any ideas would be greatly appreciated.

Regards,
Jesse

 

[George Stolz]

What kind of service does it have? 480V ungrounded?

 

[Kessler4130]

The service is single phase 120/240v, talking to my friend now and he is there and said he grabbed the downspout with wet hands and got a little shock. Everything that is metal seems to carry the voltage. As far as I know the only ground they use is the water ground being an older structure, and being a pump station tied to several others I don't know if that would effect it in any way.

 

[Kessler4130]

The voltage L1/N is 119 L2/N is 121 from the xformer with the main disconnect turned off, and the main service disconnect is 400 amps fed from a pole mount transformer.

 

[brian john]

We are talking 15 VAC to ground from the NEUTRAL?

Check the main bonding jumper.
What type of meter.
Is the surface he is measuring to suppose to be grounded?
Has he verified the surface he is measuring to is grounded?
Does he get this reading at the main service?
Does the reading increase as he gets further away from the main service.

 

[LarryFine]

It may be that the earth itself is energized.

 

[Kessler4130]

It may be that the earth itself is energized.

This was one of the things they were thinking, the voltage varies from 15v at the first building to about 5 volts a few buildings down. Apparently the buildings were all sub-fed by the main pump house long ago and since have all had thier own services added. I know it is very difficult to help with the lack of information and I appologise, I have not seen this for myself and probably never will I am just trying to shed some light on it for my friend.

He said they have checked the water ground, and the bonding jumpers all are supposedly tight. So the reading is actually decreasing the further he gets from the main building now, but beings they all have seperate services now I am guess it originates in the building with the highest voltage reading. They are reading this to earth, and it is reading from everything, from the panel box, to the aluminum awning that is bolted to a metal door frame. If it is metal it is reading a voltage of 15 volts, that is what was kind of leading to believe maybe its actually the earth itself, but I don't have the experience with this type of thing to prove or disprove it.


So in short:

Check the main bonding jumper. Yes, he has
What type of meter. Not sure
Is the surface he is measuring to suppose to be grounded? In most cases yes
Has he verified the surface he is measuring to is grounded? Some
Does he get this reading at the main service? Yes
Does the reading increase as he gets further away from the main service. No

 

[beanland]

Elevated Neutral

Elevated Neutral

On the POCO system, it is not unusual for the neutral to be elevated above ground. Since the service neutral is bonded to the POCO neutral, the service neutral will have the POCO neutral voltage. When you test relative to earth (remote ground rod), you are measuring the POCO neutral to earth potential. Such a condition can easily occu is the POCO system is unbalanced (often) and the POCO grounds are poor (normal.) Some call this "stray current" but it is actually "elevated neutral." If this is a problem, more/better bonds to equipment are needed for safety. On a dairy farm, 1V is too much. This gets into "equipotential" bonding.

 

[LarryFine]

Check the main bonding jumper. Yes, he has
What type of meter. Not sure
Is the surface he is measuring to suppose to be grounded? In most cases yes
Has he verified the surface he is measuring to is grounded? Some
Does he get this reading at the main service? Yes
Does the reading increase as he gets further away from the main service. No

One more: Does the voltage remain when the main for the worst building is turned off?

 

[finster1]

neutral bad

neutral bad

Sounds to me that you lost the neutral or there is a real poor connection causing the return path to find ground instead of a solid neutral. Take an amprobe and clamp it on a waterpipe....if you have current you've found the problem.

 

[Kessler4130]

One more: Does the voltage remain when the main for the worst building is turned off?

yes it does

 

[catchtwentytwo]

Take the reading with an analog-type voltmeter (like a Simpson 260). That type of meter has a low enough input impedance to rule out "Phantom Voltage"

 

[Kessler4130]

Take the reading with an analog-type voltmeter (like a Simpson 260). That type of meter has a low enough input impedance to rule out "Phantom Voltage"

Well at first I wasn't giving it any thought until he told me that several people are getting a little buzz by touching various things while grounded. They aren't getting knocked out of thier boots or anything but it is certainly noticeable.

 

[Kessler4130]

Just a follow-up, had the poco come out after doing as finster1 reccomended and amprobed the EGC and got 1.5 amps. Well the POCO apparently hooked up a phase from one of the transformers directly to the neutral (there were 4 transformers on the pole for different services and a common ground between all of the XO terminals. So the problem is solved there is now no voltage on the building steel, thanks for all your help.

Jesse