user4818

I understand the bonding requirements in substations. What I'm not understanding are the earthing requirements. Is this yet another example of "Lets connect this stuff to as much dirt as possible so our electrical system will be safe and happy" ?

Or as stated in another thread, since there is so much neutral current flowing back to the source via the earth, that this connection is actually needed?

Edumacate me!

BBQ

Are you forgetting that at high voltages the earth can open an OCPD?

user4818

Not at all.

BBQ

So how is the POCOs grounding of the earth multiple times any different than us bonding the same raceway at every box? They are trying to ensure a low impedance fault path.

The problem is not the multiple grounding connections the problem is using one conductor as both a circuit conductor and a bonding conductor and that is not going to change.

donaldelectrician

LPS System ?




Don

tkb

Cadweld has molds for splicing the rods.

http://www.erico.com/cadweldCatalog/...leToGrdRod.pdf
Go to page 14. Mold type GB.

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kevink1955

Years back I did an antenna tower grounding project that got 3 24' rods. They were 3 8' rods cad welded together, I did not think a cad weld would take the pounding but it worked out fine. We do have sandy soil do the drive was not to hard. As the water table is around 8' here, 16' of rod is in water. If that dont tell the lightning where to go I do not know what will.

They do have a strike counter on the tower and last time I heard it was taking around 5 strikes a year with no equpment damage.

sbrn33

How do you know the cadweld held up?

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Stop trying to think logically, it won't help you here. Just do as we say and everything will be alright.

brian john

If properly completed the Cadwelded rods should hold up adequately. This is not something new and utilities have a history in completing or having completed installs as noted. At the higher voltages involved I would think the effects of utilizing the Earth for grounding purpose is more effective.

I am big on pointing out the waste of some of the voodoo grounding practices implemented in attempt to resolve power quality issues. In this case I think the utilities experience MAY have insight into their needs for an deep Earth Ground.

Hopefully this is based on testing the utilities have done and not some random specification pulled from the shelf of a retired engineer.

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Brian John
Leesburg, VA

donaldelectrician

" Lightning cant hit the same spot twice "

Don

PS Mayby the site prep plans will help him out . He will make those connections while they backfill and tamp.

al_smelter

I don't understand the fuss. A properly executed Cadweld joint will be as strong as the rods themselves. The fusion is complete throughout the joint. There essentially is no joint at all.

I also don't get length argument. I have driven a hellufalot longer rods than a mere 30 ft. Years ago we drove 60 ft (nasty sandy dry soil) with still awful readings, and on the 70th ft joint, one of the guys saw it coming up out of the ground around 40 ft away from where it went in. It made a complete U turn.

Point is, you're looking for a resistance value that is specified, and evidently the powers in this case know (assume) that X number of 30 ft rods will get them the value they need or want. But it isn't abnormal to go a lot deeper than that if the soil in the area suucks.

MasterE

[quote=donaldelectrician;740229]" Lightning cant hit the same spot twice "


Yes it can ,and it does.

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Soon after the Sweetness of Low Prices are forgotten,
The Bitterness of Poor Quality Remains.

Dhfisher

Last weak I coundt spel enganear this weak I are one.

CraigV

Tell that to Lee Trevino.

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Was born in HACKensack, NJ

donaldelectrician

LEE TREVINO QUOTE • "If you are caught on a golf course during a storm and are afraid of lightning, hold up a 1-iron. Not even God can hit a 1-iron."




DON

Dnkldorf

Lightning hits the Empire state building a couple hundred times a yr, doesn't it?