Bar holing and buried electrical lines

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mikecj

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Everyone,

In the gas industry plunger bars are used to detect and locate gas leaks. As you can imagine there is the potential for coming into contact with buried electrical lines. I'm trying to pull together a hazard assessment so I can determine the required PPE. I've reviewed 70E and it did not provide much guidance for this particular task. The plunger is rated for 10 kV. So a couple of questions:
1. What voltages are normally found in buried lines? You can assume the gas and electrical lines are in close proximity so induced voltage comes into play.
2. What PPE woul you recommend? How about arc rated clothing?

Thanks,

MikeCJ
 
mikecj said:
Everyone,

In the gas industry plunger bars are used to detect and locate gas leaks. As you can imagine there is the potential for coming into contact with buried electrical lines. I'm trying to pull together a hazard assessment so I can determine the required PPE. I've reviewed 70E and it did not provide much guidance for this particular task. The plunger is rated for 10 kV. So a couple of questions:
1. What voltages are normally found in buried lines? You can assume the gas and electrical lines are in close proximity so induced voltage comes into play.
2. What PPE woul you recommend? How about arc rated clothing?

Thanks,

MikeCJ
Click to expand...
Voltage can be anywhere from 120 VDC on communications lines to 69,000 (maybe even more in some cases) AC for power transmission lines.

You don't want to be nearby if you probe into the 69K line.

Local rural POCO fairly recently was repairing an underground portion of a transmission line and for whatever reason had a bad splice kit - they energized the line with trench still open but was smart enough to not stand near the open trench. It arced over to barbed wire fence followed it for over a mile and arced over to a couple telephone pedestals along the way and caused damage to phone lines on a couple properties in the area. Kind of luck that was all the damage there was, and nobody was hurt. That line was 34.5 kV.
 
ptonsparky said:
Diggers hotline before you so much as poke a flag in the ground.
Click to expand...
Yes, and if you are close, in many cases within 18" plus 1/2 of the diameter of the located underground, you can't just poke holes in the ground. Some areas require the use of a vacuum excavator if you are within that distance from the locate mark.
 
Don't always trust locates either.

Just last week the locate company located the primary to a 750 kva trans. The diggers then proceeded to dig over to the LV side of the trans so we could pull a second service out of it. The power company was called to unlock the trans so the conduits could get stubbed in. At this point they realized the locate company had marked out an abandoned primary feed into the trans, the wires were cut off flush just above the dirt inside the trans. The diggers about had a heart attack when they realized they had dug their ditch right over the actual ENERGIZED primary that had NOT been marked out, missing it only by 6". Had they went half a scoop deeper, and I might be typing a different story...
 
kwired said:
Voltage can be anywhere from 120 VDC on communications lines to 69,000 (maybe even more in some cases) AC for power transmission lines.

You don't want to be nearby if you probe into the 69K line.

Local rural POCO fairly recently was repairing an underground portion of a transmission line and for whatever reason had a bad splice kit - they energized the line with trench still open but was smart enough to not stand near the open trench. It arced over to barbed wire fence followed it for over a mile and arced over to a couple telephone pedestals along the way and caused damage to phone lines on a couple properties in the area. Kind of luck that was all the damage there was, and nobody was hurt. That line was 34.5 kV.
Click to expand...

Just realized I said 120 VDC on communications when I meant to say 12VDC.
 
"Call before you dig" signs everywhere. For a reason. Had a cable company dig for a new pedestal at an intersection in town. Knew what they were doing, so didn't need a locate. Pounded a ground rod through a 7200 volt underground cable. We got called because the traffic light and the 7-eleven were out of of power. Located the fault, dug it up and they hit it dead center. Both were still alive, but they got kinda pale when they realized what they'd done. Not to mention, their company got the bill for the repair.

Calling is free....fixing is not!
 
Pad mount transformer primary

Pad mount transformer primary

Pole with 3Ph 7200/12470V Cable coming down it. Pad mounted Transformer 20 feet away. Backhoe operator digging a sewer trench paralleling the pole line. When he got between the pole and transformer he dug up the primary cable. Pretty impressive. But it could have been worse, He missed the High Pressure Gas line 6 inches lower. It never occurred to him that the cable going down the pole would go to the transformer. Call MissUtility? Huh??
 
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