Low Current on Building Steel Ground

[waltppiva]

In a 2 yr old Admin bldg I measured 1.5 to 2 amps at various points in the bldg steel grounding system; transformer ground from case to steel, steel girder ground wire. The site people are very concerned that this is a serious problem. I opened all the transformers and most of the panels in the building verifying proper neutral-ground bonds. I found nothing out of the ordinary. Can someone explain what could cause this low ground current, and is it a problem to be concerned about?

Thanks for your help.

Weakness of attitude becomes weakness of character.
-- Albert Einstein

 

[don_resqcapt19]

Walt,
Exactly where are you measuring this current? The most common cause would be an illegal neutral to ground connection.
Don

 

[tonyi]

Maybe one of the neighbors has a loose neutral in their service if all your stuff looks proper. That would cause neighboring ground systems to return the neighbor's neutral current. If you can kill the whole place at some convenient time and check it again with everything off, you could eliminate this possibility.

 

[waltppiva]

Don, I measured the current on the ground wire coming out of the transformer case connected to the bldg steel, on a coupletransformers. I also measured it on the ground wire connecting two other bldg steel girders. I've worked with ground currents before, and I am familiar with neutral-ground bonds causing ground current. But should 1.5 amps be a serious concern? I've heard of power supplies in small UPS units causing ground current because they have the N-G bonded. If this is the case, we may just be on a wile goose chase.

Thanks
Walt

 

[ramsy]

Can we put a wire-tracer signal on the building steel and sweep the panels with the pick up.
Something like the PASAR AMPROBE AT-2005

 

[don_resqcapt19]

Walt,
I have no idea what amount of current would cause a problem.
Don

 

[bob]

If the building is large would not you have a normal voltage gradient
between the structural steel in the ground and thus a current flow?

 

[dereckbc]

My two cents worth. If the building is large with a lot of cable distribution, likely cause is just capacitive coupling between P & G wires.

Another possibility is HID lighting. The ballast are known to leak.

As to your question is 1.5-amps a lot depends on the size of the service and the amount of load. For example if it is a 1000-amp service with 500-amp load, no problem IMO, it's leakage