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Potential underground distribution fault? #207377 10/21/12 11:11 PM
Joined: Oct 2006
Posts: 745
E
EV607797 Offline OP
Member
Hey, guys. I've only worked a maximum of 480 volts and don't know much about voltages above this. Here's my dilemma:

I live in a townhouse community with underground distribution. In my row of townhouses, as with all others, there is a transformer at the end of my row with joint-use trenches for service laterals to each meter (200A each using 1/0 AL triplex). My guess is that the 7.2 KV feed to the transformer is buried first, then the individual service drops are buried a foot or so above it.

When it gets cool at night and dew forms on the grass, or when we have especially humid weather, the tips of the grass along this trench line glow like smoldering embers for a few seconds at a time. No, I'm not crazy. I've already questioned things like reflective light, etc, but I can walk up and pinch these grass tips and the glowing goes out.

My next door neighbor doesn't have a single blade of grass growing along this trench line, despite the fact that the landscaping crew does a great job of aerating the soil, planting seed, etc.

I suspect that there is a fault in the high voltage distribution cable feeding the transformer. I guess that a fault in a service lateral could also be causing this, but I would think that it would fail a lot faster resulting in an outage for one customer.

Now that I've written a book on the subject, is it possible for a cable fault to allow enough leakage to kill the grass above it and to cause the 'glowing grass tips' situation to occur within say, 25 feet of it?

I want to report this to the POCO, but I'm afraid that the minimum-wage clerk at the call center will write this up as a drunken customer. Furthermore, I don't want to have them digging up my neighbor's yard for nothing.

I guess what I'm getting at is to ask this question: Would a fault in a high-voltage cable cause something like this? Should I be concerned? Should I just zip my lips and just wait for the fault that I suspect to just completely fail and then not have to question myself again? Your thoughts?


---Ed---

"But the guy at Home Depot said it would work."
Work Gear for Electricians and the Trades
Re: Potential underground distribution fault? [Re: EV607797] #207379 10/22/12 03:27 AM
Joined: Jul 2004
Posts: 9,571
G
gfretwell Online Content
Member
I think I would start with a long piece of THHN firmly attached to the best ground I can find as a meter lead and stick a screwdriver into the dirt along this line hooked to the other meter lead.
I am not sure how good this test would be but at least it is a place to start. Do a good one and a suspect one.


Greg Fretwell
Re: Potential underground distribution fault? [Re: gfretwell] #207381 10/22/12 11:43 AM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline
Member
Greg, being that there's potential for high voltage, would he need a HV rated meter? Most meters go to only 600 volts. I know of an electrician who died by grabbing the wrong meter and surcharge it in a switch gear and it blew up on him


"Live Awesome!" - Kevin Carosa
Re: Potential underground distribution fault? [Re: EV607797] #207382 10/22/12 01:02 PM
Joined: Jul 2004
Posts: 9,571
G
gfretwell Online Content
Member
I doubt you would ever see that much voltage in the dirt but if you really want to be on the safe side, sneak up on it. Try your first test many feet away.
Do animals avoid the area?


Greg Fretwell
Re: Potential underground distribution fault? [Re: EV607797] #207383 10/22/12 08:17 PM
Joined: Apr 2002
Posts: 7,234
HotLine1 Offline
Member
Ed:

IMHO, I would contact the POCO, hopefully you know one of the wiring or meter inspectors. If not, you may know an EC that has a POCO contact.



John
Re: Potential underground distribution fault? [Re: EV607797] #207384 10/23/12 10:22 AM
Joined: Oct 2006
Posts: 745
E
EV607797 Offline OP
Member
Actually, my best friend is a supervisor for our POCO and I ran this by him. He agrees that there is a fault in the immediate vicinity and that they should be called. Since I'm renting, I'm going to have the property management take care of handling this. Thanks for the suggestions, guys.


---Ed---

"But the guy at Home Depot said it would work."
Re: Potential underground distribution fault? [Re: EV607797] #207408 10/25/12 03:32 AM
Joined: Oct 2000
Posts: 2,721
Scott35 Online Happy
Broom Pusher and
Member
I wonder if the Transformer(s) are connected as MGCN (Multi-Grounded Common Neutral), and there is an issue with the bonding link between Primary and Secondary Grounded Conductors???

There also may be leakage between the direct buried cables, and / or to some other Utility (i.e. Water, Gas, Telephone, CATV).

The scenario sounds similar to applying 120V to an "isolated" driven Ground Rod (Rod is not connected to anything); Earthworms appear at the Ground surface, and start Hula Dancing... wink

-- Scott (EE)


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Potential underground distribution fault? [Re: EV607797] #207519 11/03/12 12:02 AM
Joined: Jan 2005
Posts: 354
P
pdh Offline
Member
Do these glowing grass tips have that 120 cycle per second blinking effect?

Last edited by pdh; 11/03/12 12:02 AM.
Re: Potential underground distribution fault? [Re: EV607797] #207684 11/19/12 11:28 PM
Joined: Feb 2004
Posts: 1,437
Lostazhell Offline
Member
Start off using an EMF tester (hot stick) if it glows when you're still 10' away from the area in question, I'd let the utility handle it. There could be a breakdown of the Faraday cage/shield in one of the conductors from a tree root or possibly a pinhole in the insulation from when it was first installed just now rearing it's ugly appearance.

Re: Potential underground distribution fault? [Re: EV607797] #207748 11/24/12 12:22 PM
Joined: Feb 2002
Posts: 2,233
H
harold endean Offline
Member
I have heard of such problems. There was "Stray voltage" in the earth and you can feel it if you were barefoot and you touched a grounded object like a metal hand rail, or outside hose bib.

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