The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
Texas_Ranger 8
sparkyinak 7
Trumpy 6
Who's Online
1 registered (geoff in UK), 133 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Page 1 of 2 1 2 >
Topic Options
Rate This Topic
#207377 - 10/21/12 09:11 PM Potential underground distribution fault?
EV607797 Offline
Member

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
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."

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#207379 - 10/22/12 01:27 AM Re: Potential underground distribution fault? [Re: EV607797]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
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

Top
#207381 - 10/22/12 09:43 AM Re: Potential underground distribution fault? [Re: gfretwell]
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1295
Loc: Alaska
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

Top
#207382 - 10/22/12 11:02 AM Re: Potential underground distribution fault? [Re: EV607797]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
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

Top
#207383 - 10/22/12 06:17 PM Re: Potential underground distribution fault? [Re: EV607797]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
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

Top
#207384 - 10/23/12 08:22 AM Re: Potential underground distribution fault? [Re: EV607797]
EV607797 Offline
Member

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
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."

Top
#207408 - 10/25/12 01:32 AM Re: Potential underground distribution fault? [Re: EV607797]
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
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!

Top
#207519 - 11/02/12 10:02 PM Re: Potential underground distribution fault? [Re: EV607797]
pdh Offline
Member

Registered: 01/20/05
Posts: 354
Do these glowing grass tips have that 120 cycle per second blinking effect?


Edited by pdh (11/02/12 10:02 PM)

Top
#207684 - 11/19/12 08:28 PM Re: Potential underground distribution fault? [Re: EV607797]
Lostazhell Offline
Member

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
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.

Top
#207748 - 11/24/12 09:22 AM Re: Potential underground distribution fault? [Re: EV607797]
harold endean Offline
Member

Registered: 02/16/02
Posts: 2248
Loc: Boonton, NJ
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.

Top
Page 1 of 2 1 2 >



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals