Welder Ground Lead

[FionaZuppa]

I think the more general point is that lightning currents are not comparable to welding currents in either behavior or duration. It does not follow that the welding currents are safe because lightning currents may, in the odd circumstance, travel over the same metal without causing damage. And of course, sometimes lightning on EGCs does cause damage.

that wasnt the point, and i dont think anyone was stating such.

the point was, LPS is to be tied to GEC. ok, which also means its tied to EGC. ok, and some say it doesnt matter that its tied to EGC because like dumping a buck of water in sink it all goes down the drain, except one minor fact, GEC also has ohms, which means a % of the LPS amps also runs over EGC to wherever, hence why i said LPS systems should really be isolated from the wiring of a structure. but, isolation is not ez w/ lightning.

i think iron structures, the iron is the GEC and not EGC, so they can clamp a beam near the welder and then run out 100ft (or whatever) to stick weld, etc.

as for welding amps on EGC (one leg of the welder), that can be an issue depending on how the EGC stuff is deployed/connected. however, a burn hole in MC might be amps taking a new route, and it created a haz point on the MC and it eventually melts, which can obviously cause an issue for the wires inside.

 

[mivey]

the point was, LPS is to be tied to GEC. ok, which also means its tied to EGC. ok, and some say it doesnt matter that its tied to EGC because like dumping a buck of water in sink it all goes down the drain, except one minor fact, GEC also has ohms, which means a % of the LPS amps also runs over EGC to wherever, hence why i said LPS systems should really be isolated from the wiring of a structure. but, isolation is not ez w/ lightning.

A drain is the only way out. Nothing says there is only one drain. The bigger the drain (the better the connection and path to Earth) the more amps it gets.

A LPS is not going to have a connection/path to Earth on one side of the building only. That would expose the EGC on the other side and make it carry the brunt of the strikes on that side. The LPS will shunt/shield and take the brunt of the strike. Like the bumper on a car takes the worst so the passengers can survive.

 

[mivey]

hence why i said LPS systems should really be isolated from the wiring of a structure. but, isolation is not ez w/ lightning.

Do you have evidence to support that isolating the LPS rather than bonding is a better solution?

 

[FionaZuppa]

Do you have evidence to support that isolating the LPS rather than bonding is a better solution?

are you really asking this question???

IEC 62305

Let's take a look in slow motion at what a typical 100 kA lightning current can do by induced coupling to a panel or similar. Bear in mind, this is an induced (secondary) effect and not even the full directly connected lightning current itself.

 

[FionaZuppa]

just because its in NFPA books doesnt always mean thats the right/best way !!

 

[mivey]

are you really asking this question???

Well, yes. Yes I am.

 

[ActionDave]

just because its in NFPA books doesnt always mean thats the right/best way ...

It's not just the nfpa, although they're pretty reliable, Motorola's R56 standard doesn't have Anything isolated.

 

[FionaZuppa]

It's not just the nfpa, although they're pretty reliable, Motorola's R56 standard doesn't have Anything isolated.

seems to be varying views on the subject of isolated vs non-isolated LPS then........
i am in the isolation camp.

i think we see it bonded to gec only because the LPS is typically not an isolated one, hence its better to tie it to gec to keep it in a metal path.

isolated LPS is also magnitudes harder to do for say the Empire State Building (or the like).

 

[mivey]

did i miss something. doesnt the EGC have to tie to the GEC at some point?
once tied, 4 million volts travels everywhere, everything has some ohms :thumbsup:

...the point was, LPS is to be tied to GEC.
...
which means a % of the LPS amps also runs over EGC to wherever, hence why i said LPS systems should really be isolated from the wiring of a structure. but, isolation is not ez w/ lightning.

Do you have evidence to support that isolating the LPS rather than bonding is a better solution?

are you really asking this question???

IEC 62305

The isolation IEC 62305 is talking about is using a shielding scheme, like you would see at a power substation. The isolation does not mean not connected to the electrical system as you have proposed. It is still bonded.

 

[mivey]

isolated LPS is also magnitudes harder to do for say the Empire State Building (or the like).

Shielding depends on the shield being the tallest thing around so there is the rub with isolating the ESB.

That said, you can still cover a tall building and have lightning electrodes installed taller than stuff on the roof (again, a problem for the ESB because of the very tall stuff on the roof, like attennas).

 

[winnie]

IMHO the LPS ground system _must_ be bonded to all other grounding electrodes, otherwise earth 'step potentials' could be coupled via the _separate_ grounding electrodes to cause differences of potential on different metal components which are separately grounded.

With that said, it would seem to me that the bonding and lightning down conductors should be routed so that current is not likely to be coupled into the building electrical system via these bonds.

When you consider lightning strikes, a direct hit is much less likely than a nearby hit which causes ground currents. You must design for these earth currents, not just the direct hit.

-Jon

 

[jaggedben]

that wasnt the point, and i dont think anyone was stating [that lightning is comparable to welding current]

MAC702 seemed to be saying so, to me, in posts #42 and #49. This wasn't originally a thread about lightning protection. Regardless of the best practices with respect to bonding an LPS, I hope we can agree that it has little to no bearing on the safety of welding currents such as those brought up in the OP.

 

[FionaZuppa]

With that said, it would seem to me that the bonding and lightning down conductors should be routed so that current is not likely to be coupled into the building electrical system via these bonds.

-Jon

if the LPS is tied to GEC (and the EGC) how can that also be "...routed so that current is not likely to be coupled into the building electrical system"?? 100kA and 4Mvolts with just a fraction of an ohm in GEC means lots of volts and amps across the GEC & EGC, they are just shunts at that point.

and if lightning is a ground strike then its not hitting the LPS??


an isolated LPS that uses say 3/4"dia steel rod in center of a 4"dia pvc pipe filled with glass bead, and then tied to a 20ft ground rod, seems to me a better way. but, if the building is 1500ft tall then obviously not a real ez way to construct it.

 

[MAC702]

MAC702 seemed to be saying so, to me, in posts #42 and #49. This wasn't originally a thread about lightning protection. Regardless of the best practices with respect to bonding an LPS, I hope we can agree that it has little to no bearing on the safety of welding currents such as those brought up in the OP.

I don't think I inferred that welding and lightning currents were the same, just that the latter is possibly a noteworthy thing to the discussion. I wouldn't have thought it has "little to no bearing..." I thought I had freely admitted to no expertise in lightning protection.

 

[jaggedben]

if the LPS is tied to GEC (and the EGC) how can that also be "...routed so that current is not likely to be coupled into the building electrical system"?? 100kA and 4Mvolts with just a fraction of an ohm in GEC means lots of volts and amps across the GEC & EGC, they are just shunts at that point.

But I don't believe there's any particular reason why a GEC or EGC should see the full lightning voltage if only one end is connected to ground and it's not a direct strike. In any case, it is an not apples to apples comparison to a welding current.

I don't think I inferred that welding and lightning currents were the same, just that the latter is possibly a noteworthy thing to the discussion. I wouldn't have thought it has "little to no bearing..." I thought I had freely admitted to no expertise in lightning protection.

'little to no bearing' is my opinion. They are just very different phenomena. If you design a road for racecars, you don't test it by running dump trucks on it, or vice versa. Also, for what it's worth, welding currents are comparable to NEC applications and the NEC can be read to prohibit using random EGCs as a welding return, as Goldigger said a long time ago in this thread (objectionable current). The NEC does not cover lightning protection, so judging EGCs by their performance in a lightning storm isn't a comparable standard. Apples and oranges.

 

[GoldDigger]

But I don't believe there's any particular reason why a GEC or EGC should see the full lightning voltage if only one end is connected to ground and it's not a direct strike. In any case, it is an not apples to apples comparison to a welding current.



'little to no bearing' is my opinion. They are just very different phenomena. If you design a road for racecars, you don't test it by running dump trucks on it, or vice versa. Also, for what it's worth, welding currents are comparable to NEC applications and the NEC can be read to prohibit using random EGCs as a welding return, as Goldigger said a long time ago in this thread (objectionable current). The NEC does not cover lightning protection, so judging EGCs by their performance in a lightning storm isn't a comparable standard. Apples and oranges.

FWIW, in terms of electrical safely rather than design and use, a transformer-isolated welding machine could be considered to incorporate an SDS.