High impedance efffects on master grounds

[jdbiederer]

In the present problems with copper thefts, we have been looking at solutions to a telecom site ground loss. Some vendors have proposed encasing the outside collection ground bars in cages. My belief is the use of a ferris material surronding the bar will act as a choke and result in a high impedance ground path. I suggested the vendor consider an aluminum case, but my associate feels even aluminum will create a high impedance. From my recollection of physics, that will only occur with a ferromagnetic effect, hence not using a ferris material to encase the bus. What am I missing here?

 

[RayS]

wow. That's bad when you gotta put a cage around a ground to keep the thieves off it.

If you bond the cage to the conductor, the impedance should be lower as the cage will take most of the current flow, especially at higher freq's. Now you just gotta keep the cage from corroding, and hope the price of scrap iron doesn't rise...

As to your question, the ferrous materials do have a very much larger effect on inductance. I don't know the calculation, but at a few inches away it may not be very significant.

Could you sleeve it in pvc? encase it in concrete? wrap an alarm loop around it?

 

[jdbiederer]

Yes, the druggies will go for anything to get a hit, and with the price of copper... do you see any way that an aluminum housing would create any impedance on the ground system? I would guess that some current would be induced in the aluminum, but I can't imagine, without the existance of a magnetic pulse, that any net affect as a choke would result?